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GCC(1)				      GNU				GCC(1)



NAME
       gcc - GNU project C and C++ compiler

SYNOPSIS
       gcc [-c|-S|-E] [-std=standard]
	   [-g] [-pg] [-Olevel]
	   [-Wwarn...] [-Wpedantic]
	   [-Idir...] [-Ldir...]
	   [-Dmacro[=defn]...] [-Umacro]
	   [-foption...] [-mmachine-option...]
	   [-o outfile] [@file] infile...

       Only the most useful options are listed here; see below for the
       remainder.  g++ accepts mostly the same options as gcc.

DESCRIPTION
       When you invoke GCC, it normally does preprocessing, compilation,
       assembly and linking.  The "overall options" allow you to stop this
       process at an intermediate stage.  For example, the -c option says not
       to run the linker.  Then the output consists of object files output by
       the assembler.

       Other options are passed on to one stage of processing.	Some options
       control the preprocessor and others the compiler itself.	 Yet other
       options control the assembler and linker; most of these are not
       documented here, since you rarely need to use any of them.

       Most of the command-line options that you can use with GCC are useful
       for C programs; when an option is only useful with another language
       (usually C++), the explanation says so explicitly.  If the description
       for a particular option does not mention a source language, you can use
       that option with all supported languages.

       The gcc program accepts options and file names as operands.  Many
       options have multi-letter names; therefore multiple single-letter
       options may not be grouped: -dv is very different from -d -v.

       You can mix options and other arguments.	 For the most part, the order
       you use doesn't matter.	Order does matter when you use several options
       of the same kind; for example, if you specify -L more than once, the
       directories are searched in the order specified.	 Also, the placement
       of the -l option is significant.

       Many options have long names starting with -f or with -W---for example,
       -fmove-loop-invariants, -Wformat and so on.  Most of these have both
       positive and negative forms; the negative form of -ffoo is -fno-foo.
       This manual documents only one of these two forms, whichever one is not
       the default.

OPTIONS
   Option Summary
       Here is a summary of all the options, grouped by type.  Explanations
       are in the following sections.

       Overall Options
	   -c  -S  -E  -o file	-no-canonical-prefixes -pipe  -pass-exit-codes
	   -x language	-v  -###  --help[=class[,...]]	--target-help
	   --version -wrapper @file -fplugin=file -fplugin-arg-name=arg
	   -fdump-ada-spec[-slim] -fada-spec-parent=unit -fdump-go-spec=file

       C Language Options
	   -ansi  -std=standard	 -fgnu89-inline -aux-info filename
	   -fallow-parameterless-variadic-functions -fno-asm  -fno-builtin
	   -fno-builtin-function -fhosted  -ffreestanding -fopenmp
	   -fms-extensions -fplan9-extensions -trigraphs  -traditional
	   -traditional-cpp -fallow-single-precision  -fcond-mismatch
	   -flax-vector-conversions -fsigned-bitfields	-fsigned-char
	   -funsigned-bitfields	 -funsigned-char

       C++ Language Options
	   -fabi-version=n  -fno-access-control	 -fcheck-new
	   -fconstexpr-depth=n	-ffriend-injection -fno-elide-constructors
	   -fno-enforce-eh-specs -ffor-scope  -fno-for-scope
	   -fno-gnu-keywords -fno-implicit-templates
	   -fno-implicit-inline-templates -fno-implement-inlines
	   -fms-extensions -fno-nonansi-builtins  -fnothrow-opt
	   -fno-operator-names -fno-optional-diags  -fpermissive
	   -fno-pretty-templates -frepo	 -fno-rtti  -fstats
	   -ftemplate-backtrace-limit=n -ftemplate-depth=n
	   -fno-threadsafe-statics -fuse-cxa-atexit  -fno-weak	-nostdinc++
	   -fno-default-inline	-fvisibility-inlines-hidden
	   -fvisibility-ms-compat -fext-numeric-literals -Wabi
	   -Wconversion-null  -Wctor-dtor-privacy -Wdelete-non-virtual-dtor
	   -Wliteral-suffix -Wnarrowing -Wnoexcept -Wnon-virtual-dtor
	   -Wreorder -Weffc++  -Wstrict-null-sentinel -Wno-non-template-friend
	   -Wold-style-cast -Woverloaded-virtual  -Wno-pmf-conversions
	   -Wsign-promo

       Objective-C and Objective-C++ Language Options
	   -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime
	   -fno-nil-receivers -fobjc-abi-version=n -fobjc-call-cxx-cdtors
	   -fobjc-direct-dispatch -fobjc-exceptions -fobjc-gc -fobjc-nilcheck
	   -fobjc-std=objc1 -freplace-objc-classes -fzero-link -gen-decls
	   -Wassign-intercept -Wno-protocol  -Wselector
	   -Wstrict-selector-match -Wundeclared-selector

       Language Independent Options
	   -fmessage-length=n -fdiagnostics-show-location=[once|every-line]
	   -fdiagnostics-color=[auto|never|always]
	   -fno-diagnostics-show-option -fno-diagnostics-show-caret

       Warning Options
	   -fsyntax-only  -fmax-errors=n  -Wpedantic -pedantic-errors -w
	   -Wextra  -Wall  -Waddress  -Waggregate-return
	   -Waggressive-loop-optimizations -Warray-bounds -Wno-attributes
	   -Wno-builtin-macro-redefined -Wc++-compat -Wc++11-compat
	   -Wcast-align	 -Wcast-qual -Wchar-subscripts -Wclobbered  -Wcomment
	   -Wconversion	 -Wcoverage-mismatch  -Wno-cpp	-Wno-deprecated
	   -Wno-deprecated-declarations -Wdisabled-optimization
	   -Wno-div-by-zero -Wdouble-promotion -Wempty-body  -Wenum-compare
	   -Wno-endif-labels -Werror  -Werror=* -Wfatal-errors	-Wfloat-equal
	   -Wformat  -Wformat=2 -Wno-format-contains-nul
	   -Wno-format-extra-args -Wformat-nonliteral -Wformat-security
	   -Wformat-y2k -Wframe-larger-than=len -Wno-free-nonheap-object
	   -Wjump-misses-init -Wignored-qualifiers -Wimplicit
	   -Wimplicit-function-declaration  -Wimplicit-int -Winit-self
	   -Winline -Wmaybe-uninitialized -Wno-int-to-pointer-cast
	   -Wno-invalid-offsetof -Winvalid-pch -Wlarger-than=len
	   -Wunsafe-loop-optimizations -Wlogical-op -Wlong-long -Wmain
	   -Wmaybe-uninitialized -Wmissing-braces
	   -Wmissing-field-initializers -Wmissing-include-dirs -Wno-mudflap
	   -Wno-multichar  -Wnonnull  -Wno-overflow -Woverlength-strings
	   -Wpacked  -Wpacked-bitfield-compat  -Wpadded -Wparentheses
	   -Wpedantic-ms-format -Wno-pedantic-ms-format -Wpointer-arith
	   -Wno-pointer-to-int-cast -Wredundant-decls  -Wno-return-local-addr
	   -Wreturn-type  -Wsequence-point  -Wshadow -Wsign-compare
	   -Wsign-conversion  -Wsizeof-pointer-memaccess -Wstack-protector
	   -Wstack-usage=len -Wstrict-aliasing -Wstrict-aliasing=n
	   -Wstrict-overflow -Wstrict-overflow=n
	   -Wsuggest-attribute=[pure|const|noreturn|format]
	   -Wmissing-format-attribute -Wswitch	-Wswitch-default
	   -Wswitch-enum -Wsync-nand -Wsystem-headers  -Wtrampolines
	   -Wtrigraphs	-Wtype-limits  -Wundef -Wuninitialized
	   -Wunknown-pragmas  -Wno-pragmas -Wunsuffixed-float-constants
	   -Wunused  -Wunused-function -Wunused-label  -Wunused-local-typedefs
	   -Wunused-parameter -Wno-unused-result -Wunused-value
	   -Wunused-variable -Wunused-but-set-parameter
	   -Wunused-but-set-variable -Wuseless-cast -Wvariadic-macros
	   -Wvector-operation-performance -Wvla -Wvolatile-register-var
	   -Wwrite-strings -Wzero-as-null-pointer-constant

       C and Objective-C-only Warning Options
	   -Wbad-function-cast	-Wmissing-declarations
	   -Wmissing-parameter-type  -Wmissing-prototypes  -Wnested-externs
	   -Wold-style-declaration  -Wold-style-definition -Wstrict-prototypes
	   -Wtraditional  -Wtraditional-conversion
	   -Wdeclaration-after-statement -Wpointer-sign

       Debugging Options
	   -dletters  -dumpspecs  -dumpmachine	-dumpversion -fsanitize=style
	   -fdbg-cnt-list -fdbg-cnt=counter-value-list -fdisable-ipa-pass_name
	   -fdisable-rtl-pass_name -fdisable-rtl-pass-name=range-list
	   -fdisable-tree-pass_name -fdisable-tree-pass-name=range-list
	   -fdump-noaddr -fdump-unnumbered -fdump-unnumbered-links
	   -fdump-translation-unit[-n] -fdump-class-hierarchy[-n]
	   -fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline -fdump-passes
	   -fdump-statistics -fdump-tree-all -fdump-tree-original[-n]
	   -fdump-tree-optimized[-n] -fdump-tree-cfg -fdump-tree-alias
	   -fdump-tree-ch -fdump-tree-ssa[-n] -fdump-tree-pre[-n]
	   -fdump-tree-ccp[-n] -fdump-tree-dce[-n] -fdump-tree-gimple[-raw]
	   -fdump-tree-mudflap[-n] -fdump-tree-dom[-n] -fdump-tree-dse[-n]
	   -fdump-tree-phiprop[-n] -fdump-tree-phiopt[-n]
	   -fdump-tree-forwprop[-n] -fdump-tree-copyrename[-n] -fdump-tree-nrv
	   -fdump-tree-vect -fdump-tree-sink -fdump-tree-sra[-n]
	   -fdump-tree-forwprop[-n] -fdump-tree-fre[-n] -fdump-tree-vrp[-n]
	   -ftree-vectorizer-verbose=n -fdump-tree-storeccp[-n]
	   -fdump-final-insns=file -fcompare-debug[=opts]
	   -fcompare-debug-second -feliminate-dwarf2-dups
	   -fno-eliminate-unused-debug-types -feliminate-unused-debug-symbols
	   -femit-class-debug-always -fenable-kind-pass
	   -fenable-kind-pass=range-list -fdebug-types-section
	   -fmem-report-wpa -fmem-report -fpre-ipa-mem-report
	   -fpost-ipa-mem-report -fprofile-arcs -fopt-info
	   -fopt-info-options[=file] -frandom-seed=string -fsched-verbose=n
	   -fsel-sched-verbose -fsel-sched-dump-cfg
	   -fsel-sched-pipelining-verbose -fstack-usage	 -ftest-coverage
	   -ftime-report -fvar-tracking -fvar-tracking-assignments
	   -fvar-tracking-assignments-toggle -g	 -glevel  -gtoggle  -gcoff
	   -gdwarf-version -ggdb  -grecord-gcc-switches
	   -gno-record-gcc-switches -gstabs  -gstabs+  -gstrict-dwarf
	   -gno-strict-dwarf -gvms  -gxcoff  -gxcoff+ -fno-merge-debug-strings
	   -fno-dwarf2-cfi-asm -fdebug-prefix-map=old=new
	   -femit-struct-debug-baseonly -femit-struct-debug-reduced
	   -femit-struct-debug-detailed[=spec-list] -p	-pg
	   -print-file-name=library  -print-libgcc-file-name
	   -print-multi-directory  -print-multi-lib  -print-multi-os-directory
	   -print-prog-name=program  -print-search-dirs	 -Q -print-sysroot
	   -print-sysroot-headers-suffix -save-temps -save-temps=cwd
	   -save-temps=obj -time[=file]

       Optimization Options
	   -faggressive-loop-optimizations -falign-functions[=n]
	   -falign-jumps[=n] -falign-labels[=n] -falign-loops[=n]
	   -fassociative-math -fauto-inc-dec -fbranch-probabilities
	   -fbranch-target-load-optimize -fbranch-target-load-optimize2
	   -fbtr-bb-exclusive -fcaller-saves -fcheck-data-deps
	   -fcombine-stack-adjustments -fconserve-stack -fcompare-elim
	   -fcprop-registers -fcrossjumping -fcse-follow-jumps
	   -fcse-skip-blocks -fcx-fortran-rules -fcx-limited-range
	   -fdata-sections -fdce -fdelayed-branch -fdelete-null-pointer-checks
	   -fdevirtualize -fdse -fearly-inlining -fipa-sra
	   -fexpensive-optimizations -ffat-lto-objects -ffast-math
	   -ffinite-math-only -ffloat-store -fexcess-precision=style
	   -fforward-propagate -ffp-contract=style -ffunction-sections -fgcse
	   -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity
	   -fgcse-sm -fhoist-adjacent-loads -fif-conversion -fif-conversion2
	   -findirect-inlining -finline-functions
	   -finline-functions-called-once -finline-limit=n
	   -finline-small-functions -fipa-cp -fipa-cp-clone -fipa-pta
	   -fipa-profile -fipa-pure-const -fipa-reference
	   -fira-algorithm=algorithm -fira-region=region -fira-hoist-pressure
	   -fira-loop-pressure -fno-ira-share-save-slots
	   -fno-ira-share-spill-slots -fira-verbose=n -fivopts
	   -fkeep-inline-functions -fkeep-static-consts -floop-block
	   -floop-interchange -floop-strip-mine -floop-nest-optimize
	   -floop-parallelize-all -flto -flto-compression-level
	   -flto-partition=alg -flto-report -fmerge-all-constants
	   -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves
	   -fmove-loop-invariants fmudflap -fmudflapir -fmudflapth
	   -fno-branch-count-reg -fno-default-inline -fno-defer-pop
	   -fno-function-cse -fno-guess-branch-probability -fno-inline
	   -fno-math-errno -fno-peephole -fno-peephole2 -fno-sched-interblock
	   -fno-sched-spec -fno-signed-zeros -fno-toplevel-reorder
	   -fno-trapping-math -fno-zero-initialized-in-bss
	   -fomit-frame-pointer -foptimize-register-move
	   -foptimize-sibling-calls -fpartial-inlining -fpeel-loops
	   -fpredictive-commoning -fprefetch-loop-arrays -fprofile-report
	   -fprofile-correction -fprofile-dir=path -fprofile-generate
	   -fprofile-generate=path -fprofile-use -fprofile-use=path
	   -fprofile-values -freciprocal-math -free -fregmove
	   -frename-registers -freorder-blocks -freorder-blocks-and-partition
	   -freorder-functions -frerun-cse-after-loop
	   -freschedule-modulo-scheduled-loops -frounding-math
	   -fsched2-use-superblocks -fsched-pressure -fsched-spec-load
	   -fsched-spec-load-dangerous -fsched-stalled-insns-dep[=n]
	   -fsched-stalled-insns[=n] -fsched-group-heuristic
	   -fsched-critical-path-heuristic -fsched-spec-insn-heuristic
	   -fsched-rank-heuristic -fsched-last-insn-heuristic
	   -fsched-dep-count-heuristic -fschedule-insns -fschedule-insns2
	   -fsection-anchors -fselective-scheduling -fselective-scheduling2
	   -fsel-sched-pipelining -fsel-sched-pipelining-outer-loops
	   -fshrink-wrap -fsignaling-nans -fsingle-precision-constant
	   -fsplit-ivs-in-unroller -fsplit-wide-types -fstack-protector
	   -fstack-protector-all -fstack-protector-strong -fstrict-aliasing
	   -fstrict-overflow -fthread-jumps -ftracer -ftree-bit-ccp
	   -ftree-builtin-call-dce -ftree-ccp -ftree-ch
	   -ftree-coalesce-inline-vars -ftree-coalesce-vars -ftree-copy-prop
	   -ftree-copyrename -ftree-dce -ftree-dominator-opts -ftree-dse
	   -ftree-forwprop -ftree-fre -ftree-loop-if-convert
	   -ftree-loop-if-convert-stores -ftree-loop-im -ftree-phiprop
	   -ftree-loop-distribution -ftree-loop-distribute-patterns
	   -ftree-loop-ivcanon -ftree-loop-linear -ftree-loop-optimize
	   -ftree-parallelize-loops=n -ftree-pre -ftree-partial-pre -ftree-pta
	   -ftree-reassoc -ftree-sink -ftree-slsr -ftree-sra
	   -ftree-switch-conversion -ftree-tail-merge -ftree-ter
	   -ftree-vect-loop-version -ftree-vectorize -ftree-vrp
	   -funit-at-a-time -funroll-all-loops -funroll-loops
	   -funsafe-loop-optimizations -funsafe-math-optimizations
	   -funswitch-loops -fvariable-expansion-in-unroller -fvect-cost-model
	   -fvpt -fweb -fwhole-program -fwpa -fuse-ld=linker
	   -fuse-linker-plugin --param name=value -O  -O0  -O1	-O2  -O3  -Os
	   -Ofast -Og

       Preprocessor Options
	   -Aquestion=answer -A-question[=answer] -C  -dD  -dI	-dM  -dN
	   -Dmacro[=defn]  -E  -H -idirafter dir -include file	-imacros file
	   -iprefix file  -iwithprefix dir -iwithprefixbefore dir  -isystem
	   dir -imultilib dir -isysroot dir -M	-MM  -MF  -MG  -MP  -MQ	 -MT
	   -nostdinc -P	 -fdebug-cpp -ftrack-macro-expansion
	   -fworking-directory -remap -trigraphs  -undef  -Umacro -Wp,option
	   -Xpreprocessor option -no-integrated-cpp

       Assembler Option
	   -Wa,option  -Xassembler option

       Linker Options
	   object-file-name  -llibrary -nostartfiles  -nodefaultlibs
	   -nostdlib -pie -rdynamic -s	-static -static-libgcc
	   -static-libstdc++ -static-libasan -static-libtsan -shared
	   -shared-libgcc  -symbolic -T script	-Wl,option  -Xlinker option -u
	   symbol

       Directory Options
	   -Bprefix -Idir -iplugindir=dir -iquotedir -Ldir -specs=file -I-
	   --sysroot=dir --no-sysroot-suffix

       Machine Dependent Options
	   AArch64 Options -mbig-endian	 -mlittle-endian -mgeneral-regs-only
	   -mcmodel=tiny  -mcmodel=small  -mcmodel=large -mstrict-align
	   -momit-leaf-frame-pointer  -mno-omit-leaf-frame-pointer
	   -mtls-dialect=desc  -mtls-dialect=traditional -march=name
	   -mcpu=name  -mtune=name

	   Adapteva Epiphany Options -mhalf-reg-file -mprefer-short-insn-regs
	   -mbranch-cost=num -mcmove -mnops=num -msoft-cmpsf -msplit-lohi
	   -mpost-inc -mpost-modify -mstack-offset=num -mround-nearest
	   -mlong-calls -mshort-calls -msmall16 -mfp-mode=mode -mvect-double
	   -max-vect-align=num -msplit-vecmove-early -m1reg-reg

	   ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name
	   -mapcs-stack-check  -mno-apcs-stack-check -mapcs-float
	   -mno-apcs-float -mapcs-reentrant  -mno-apcs-reentrant
	   -msched-prolog  -mno-sched-prolog -mlittle-endian  -mbig-endian
	   -mwords-little-endian -mfloat-abi=name -mfp16-format=name
	   -mthumb-interwork  -mno-thumb-interwork -mcpu=name  -march=name
	   -mfpu=name -mstructure-size-boundary=n -mabort-on-noreturn
	   -mlong-calls	 -mno-long-calls -msingle-pic-base
	   -mno-single-pic-base -mpic-register=reg -mnop-fun-dllimport
	   -mpoke-function-name -mthumb	 -marm -mtpcs-frame  -mtpcs-leaf-frame
	   -mcaller-super-interworking	-mcallee-super-interworking -mtp=name
	   -mtls-dialect=dialect -mword-relocations -mfix-cortex-m3-ldrd
	   -munaligned-access

	   AVR Options -mmcu=mcu -maccumulate-args -mbranch-cost=cost
	   -mcall-prologues -mint8 -mno-interrupts -mrelax -mstrict-X
	   -mtiny-stack -Waddr-space-convert

	   Blackfin Options -mcpu=cpu[-sirevision] -msim
	   -momit-leaf-frame-pointer  -mno-omit-leaf-frame-pointer
	   -mspecld-anomaly  -mno-specld-anomaly  -mcsync-anomaly
	   -mno-csync-anomaly -mlow-64k -mno-low64k  -mstack-check-l1
	   -mid-shared-library -mno-id-shared-library  -mshared-library-id=n
	   -mleaf-id-shared-library  -mno-leaf-id-shared-library -msep-data
	   -mno-sep-data  -mlong-calls	-mno-long-calls -mfast-fp -minline-plt
	   -mmulticore	-mcorea	 -mcoreb  -msdram -micplb

	   C6X Options -mbig-endian  -mlittle-endian -march=cpu -msim
	   -msdata=sdata-type

	   CRIS Options -mcpu=cpu  -march=cpu  -mtune=cpu -mmax-stack-frame=n
	   -melinux-stacksize=n -metrax4  -metrax100  -mpdebug	-mcc-init
	   -mno-side-effects -mstack-align  -mdata-align  -mconst-align
	   -m32-bit  -m16-bit  -m8-bit	-mno-prologue-epilogue	-mno-gotplt
	   -melf  -maout  -melinux  -mlinux  -sim  -sim2 -mmul-bug-workaround
	   -mno-mul-bug-workaround

	   CR16 Options -mmac -mcr16cplus -mcr16c -msim -mint32 -mbit-ops
	   -mdata-model=model

	   Darwin Options -all_load  -allowable_client	-arch
	   -arch_errors_fatal -arch_only  -bind_at_load	 -bundle
	   -bundle_loader -client_name	-compatibility_version
	   -current_version -dead_strip -dependency-file  -dylib_file
	   -dylinker_install_name -dynamic  -dynamiclib
	   -exported_symbols_list -filelist  -flat_namespace
	   -force_cpusubtype_ALL -force_flat_namespace
	   -headerpad_max_install_names -iframework -image_base	 -init
	   -install_name  -keep_private_externs -multi_module
	   -multiply_defined  -multiply_defined_unused -noall_load
	   -no_dead_strip_inits_and_terms -nofixprebinding -nomultidefs
	   -noprebind  -noseglinkedit -pagezero_size  -prebind
	   -prebind_all_twolevel_modules -private_bundle  -read_only_relocs
	   -sectalign -sectobjectsymbols  -whyload  -seg1addr -sectcreate
	   -sectobjectsymbols  -sectorder -segaddr -segs_read_only_addr
	   -segs_read_write_addr -seg_addr_table  -seg_addr_table_filename
	   -seglinkedit -segprot  -segs_read_only_addr	-segs_read_write_addr
	   -single_module  -static  -sub_library  -sub_umbrella
	   -twolevel_namespace	-umbrella  -undefined -unexported_symbols_list
	   -weak_reference_mismatches -whatsloaded -F -gused -gfull
	   -mmacosx-version-min=version -mkernel -mone-byte-bool

	   DEC Alpha Options -mno-fp-regs  -msoft-float -mieee
	   -mieee-with-inexact	-mieee-conformant -mfp-trap-mode=mode
	   -mfp-rounding-mode=mode -mtrap-precision=mode  -mbuild-constants
	   -mcpu=cpu-type  -mtune=cpu-type -mbwx  -mmax	 -mfix	-mcix
	   -mfloat-vax	-mfloat-ieee -mexplicit-relocs	-msmall-data
	   -mlarge-data -msmall-text  -mlarge-text -mmemory-latency=time

	   FR30 Options -msmall-model -mno-lsim

	   FRV Options -mgpr-32	 -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float
	   -msoft-float -malloc-cc  -mfixed-cc	-mdword	 -mno-dword -mdouble
	   -mno-double -mmedia	-mno-media  -mmuladd  -mno-muladd -mfdpic
	   -minline-plt -mgprel-ro  -multilib-library-pic -mlinked-fp
	   -mlong-calls	 -malign-labels -mlibrary-pic  -macc-4	-macc-8 -mpack
	   -mno-pack  -mno-eflags  -mcond-move	-mno-cond-move
	   -moptimize-membar -mno-optimize-membar -mscc	 -mno-scc  -mcond-exec
	   -mno-cond-exec -mvliw-branch	 -mno-vliw-branch -mmulti-cond-exec
	   -mno-multi-cond-exec	 -mnested-cond-exec -mno-nested-cond-exec
	   -mtomcat-stats -mTLS -mtls -mcpu=cpu

	   GNU/Linux Options -mglibc -muclibc -mbionic -mandroid
	   -tno-android-cc -tno-android-ld

	   H8/300 Options -mrelax  -mh	-ms  -mn  -mexr -mno-exr  -mint32
	   -malign-300

	   HPPA Options -march=architecture-type -mbig-switch
	   -mdisable-fpregs  -mdisable-indexing -mfast-indirect-calls  -mgas
	   -mgnu-ld   -mhp-ld -mfixed-range=register-range -mjump-in-delay
	   -mlinker-opt -mlong-calls -mlong-load-store	-mno-big-switch
	   -mno-disable-fpregs -mno-disable-indexing  -mno-fast-indirect-calls
	   -mno-gas -mno-jump-in-delay	-mno-long-load-store
	   -mno-portable-runtime  -mno-soft-float -mno-space-regs
	   -msoft-float	 -mpa-risc-1-0 -mpa-risc-1-1  -mpa-risc-2-0
	   -mportable-runtime -mschedule=cpu-type  -mspace-regs	 -msio	-mwsio
	   -munix=unix-std  -nolibdld  -static	-threads

	   i386 and x86-64 Options -mtune=cpu-type  -march=cpu-type
	   -mfpmath=unit -masm=dialect	-mno-fancy-math-387 -mno-fp-ret-in-387
	   -msoft-float -mno-wide-multiply  -mrtd  -malign-double
	   -mpreferred-stack-boundary=num -mincoming-stack-boundary=num -mcld
	   -mcx16 -msahf -mmovbe -mcrc32 -mrecip -mrecip=opt -mvzeroupper
	   -mprefer-avx128 -mmmx  -msse	 -msse2 -msse3 -mssse3 -msse4.1
	   -msse4.2 -msse4 -mavx -mavx2 -maes -mpclmul -mfsgsbase -mrdrnd
	   -mf16c -mfma -msse4a -m3dnow -mpopcnt -mabm -mbmi -mtbm -mfma4
	   -mxop -mlzcnt -mbmi2 -mrtm -mlwp -mthreads -mno-align-stringops
	   -minline-all-stringops -minline-stringops-dynamically
	   -mstringop-strategy=alg -mpush-args	-maccumulate-outgoing-args
	   -m128bit-long-double -m96bit-long-double -mlong-double-64
	   -mlong-double-80 -mregparm=num  -msseregparm -mveclibabi=type
	   -mvect8-ret-in-mem -mpc32 -mpc64 -mpc80 -mstackrealign
	   -momit-leaf-frame-pointer  -mno-red-zone -mno-tls-direct-seg-refs
	   -mcmodel=code-model -mabi=name -maddress-mode=mode -m32 -m64 -mx32
	   -mlarge-data-threshold=num -msse2avx -mfentry -m8bit-idiv
	   -mavx256-split-unaligned-load -mavx256-split-unaligned-store

	   i386 and x86-64 Windows Options -mconsole -mcygwin -mno-cygwin
	   -mdll -mnop-fun-dllimport -mthread -municode -mwin32 -mwindows
	   -fno-set-stack-executable

	   IA-64 Options -mbig-endian  -mlittle-endian	-mgnu-as  -mgnu-ld
	   -mno-pic -mvolatile-asm-stop	 -mregister-names  -msdata -mno-sdata
	   -mconstant-gp  -mauto-pic  -mfused-madd
	   -minline-float-divide-min-latency
	   -minline-float-divide-max-throughput -mno-inline-float-divide
	   -minline-int-divide-min-latency -minline-int-divide-max-throughput
	   -mno-inline-int-divide -minline-sqrt-min-latency
	   -minline-sqrt-max-throughput -mno-inline-sqrt -mdwarf2-asm
	   -mearly-stop-bits -mfixed-range=register-range -mtls-size=tls-size
	   -mtune=cpu-type -milp32 -mlp64 -msched-br-data-spec
	   -msched-ar-data-spec -msched-control-spec -msched-br-in-data-spec
	   -msched-ar-in-data-spec -msched-in-control-spec -msched-spec-ldc
	   -msched-spec-control-ldc -msched-prefer-non-data-spec-insns
	   -msched-prefer-non-control-spec-insns
	   -msched-stop-bits-after-every-cycle
	   -msched-count-spec-in-critical-path
	   -msel-sched-dont-check-control-spec -msched-fp-mem-deps-zero-cost
	   -msched-max-memory-insns-hard-limit -msched-max-memory-insns=max-
	   insns

	   LM32 Options -mbarrel-shift-enabled -mdivide-enabled
	   -mmultiply-enabled -msign-extend-enabled -muser-enabled

	   M32R/D Options -m32r2 -m32rx -m32r -mdebug -malign-loops
	   -mno-align-loops -missue-rate=number -mbranch-cost=number
	   -mmodel=code-size-model-type -msdata=sdata-type -mno-flush-func
	   -mflush-func=name -mno-flush-trap -mflush-trap=number -G num

	   M32C Options -mcpu=cpu -msim -memregs=number

	   M680x0 Options -march=arch  -mcpu=cpu  -mtune=tune -m68000  -m68020
	   -m68020-40  -m68020-60  -m68030  -m68040 -m68060  -mcpu32  -m5200
	   -m5206e  -m528x  -m5307  -m5407 -mcfv4e  -mbitfield	-mno-bitfield
	   -mc68000  -mc68020 -mnobitfield  -mrtd  -mno-rtd  -mdiv  -mno-div
	   -mshort -mno-short  -mhard-float  -m68881  -msoft-float  -mpcrel
	   -malign-int	-mstrict-align	-msep-data  -mno-sep-data
	   -mshared-library-id=n  -mid-shared-library  -mno-id-shared-library
	   -mxgot -mno-xgot

	   MCore Options -mhardlit  -mno-hardlit  -mdiv	 -mno-div
	   -mrelax-immediates -mno-relax-immediates  -mwide-bitfields
	   -mno-wide-bitfields -m4byte-functions  -mno-4byte-functions
	   -mcallgraph-data -mno-callgraph-data	 -mslow-bytes  -mno-slow-bytes
	   -mno-lsim -mlittle-endian  -mbig-endian  -m210  -m340
	   -mstack-increment

	   MeP Options -mabsdiff -mall-opts -maverage -mbased=n -mbitops -mc=n
	   -mclip -mconfig=name -mcop -mcop32 -mcop64 -mivc2 -mdc -mdiv -meb
	   -mel -mio-volatile -ml -mleadz -mm -mminmax -mmult -mno-opts
	   -mrepeat -ms -msatur -msdram -msim -msimnovec -mtf -mtiny=n

	   MicroBlaze Options -msoft-float -mhard-float -msmall-divides
	   -mcpu=cpu -mmemcpy -mxl-soft-mul -mxl-soft-div -mxl-barrel-shift
	   -mxl-pattern-compare -mxl-stack-check -mxl-gp-opt -mno-clearbss
	   -mxl-multiply-high -mxl-float-convert -mxl-float-sqrt -mbig-endian
	   -mlittle-endian -mxl-reorder -mxl-mode-app-model

	   MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2
	   -mips3  -mips4  -mips32  -mips32r2 -mips64  -mips64r2 -mips16
	   -mno-mips16	-mflip-mips16 -minterlink-mips16
	   -mno-interlink-mips16 -mabi=abi  -mabicalls	-mno-abicalls -mshared
	   -mno-shared	-mplt  -mno-plt	 -mxgot	 -mno-xgot -mgp32  -mgp64
	   -mfp32  -mfp64  -mhard-float	 -msoft-float -mno-float
	   -msingle-float  -mdouble-float -mdsp	 -mno-dsp  -mdspr2  -mno-dspr2
	   -mmcu -mmno-mcu -mfpu=fpu-type -msmartmips  -mno-smartmips
	   -mpaired-single  -mno-paired-single	-mdmx  -mno-mdmx -mips3d
	   -mno-mips3d	-mmt  -mno-mt  -mllsc  -mno-llsc -mlong64  -mlong32
	   -msym32  -mno-sym32 -Gnum  -mlocal-sdata  -mno-local-sdata
	   -mextern-sdata  -mno-extern-sdata  -mgpopt  -mno-gopt
	   -membedded-data  -mno-embedded-data -muninit-const-in-rodata
	   -mno-uninit-const-in-rodata -mcode-readable=setting
	   -msplit-addresses  -mno-split-addresses -mexplicit-relocs
	   -mno-explicit-relocs -mcheck-zero-division
	   -mno-check-zero-division -mdivide-traps  -mdivide-breaks -mmemcpy
	   -mno-memcpy	-mlong-calls  -mno-long-calls -mmad  -mno-mad
	   -mfused-madd	 -mno-fused-madd  -nocpp -mfix-24k -mno-fix-24k
	   -mfix-r4000	-mno-fix-r4000	-mfix-r4400  -mno-fix-r4400
	   -mfix-r10000 -mno-fix-r10000	 -mfix-vr4120  -mno-fix-vr4120
	   -mfix-vr4130	 -mno-fix-vr4130  -mfix-sb1  -mno-fix-sb1
	   -mflush-func=func  -mno-flush-func -mbranch-cost=num
	   -mbranch-likely  -mno-branch-likely -mfp-exceptions
	   -mno-fp-exceptions -mvr4130-align -mno-vr4130-align -msynci
	   -mno-synci -mrelax-pic-calls -mno-relax-pic-calls
	   -mmcount-ra-address

	   MMIX Options -mlibfuncs  -mno-libfuncs  -mepsilon  -mno-epsilon
	   -mabi=gnu -mabi=mmixware  -mzero-extend  -mknuthdiv
	   -mtoplevel-symbols -melf  -mbranch-predict  -mno-branch-predict
	   -mbase-addresses -mno-base-addresses	 -msingle-exit
	   -mno-single-exit

	   MN10300 Options -mmult-bug  -mno-mult-bug -mno-am33 -mam33 -mam33-2
	   -mam34 -mtune=cpu-type -mreturn-pointer-on-d0 -mno-crt0  -mrelax
	   -mliw -msetlb

	   Moxie Options -meb -mel -mno-crt0

	   PDP-11 Options -mfpu	 -msoft-float  -mac0  -mno-ac0	-m40  -m45
	   -m10 -mbcopy	 -mbcopy-builtin  -mint32  -mno-int16 -mint16
	   -mno-int32  -mfloat32  -mno-float64 -mfloat64  -mno-float32
	   -mabshi  -mno-abshi -mbranch-expensive  -mbranch-cheap -munix-asm
	   -mdec-asm

	   picoChip Options -mae=ae_type -mvliw-lookahead=N
	   -msymbol-as-address -mno-inefficient-warnings

	   PowerPC Options See RS/6000 and PowerPC Options.

	   RL78 Options -msim -mmul=none -mmul=g13 -mmul=rl78

	   RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type
	   -mcmodel=code-model -mpowerpc64 -maltivec  -mno-altivec
	   -mpowerpc-gpopt  -mno-powerpc-gpopt -mpowerpc-gfxopt
	   -mno-powerpc-gfxopt -mmfcrf	-mno-mfcrf  -mpopcntb  -mno-popcntb
	   -mpopcntd -mno-popcntd -mfprnd  -mno-fprnd -mcmpb -mno-cmpb
	   -mmfpgpr -mno-mfpgpr -mhard-dfp -mno-hard-dfp -mfull-toc
	   -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-toc -m64	-m32
	   -mxl-compat	-mno-xl-compat	-mpe -malign-power  -malign-natural
	   -msoft-float	 -mhard-float  -mmultiple  -mno-multiple
	   -msingle-float -mdouble-float -msimple-fpu -mstring	-mno-string
	   -mupdate  -mno-update -mavoid-indexed-addresses
	   -mno-avoid-indexed-addresses -mfused-madd  -mno-fused-madd
	   -mbit-align	-mno-bit-align -mstrict-align  -mno-strict-align
	   -mrelocatable -mno-relocatable  -mrelocatable-lib
	   -mno-relocatable-lib -mtoc  -mno-toc	 -mlittle  -mlittle-endian
	   -mbig  -mbig-endian -mdynamic-no-pic	 -maltivec -mswdiv
	   -msingle-pic-base -mprioritize-restricted-insns=priority
	   -msched-costly-dep=dependence_type -minsert-sched-nops=scheme
	   -mcall-sysv	-mcall-netbsd -maix-struct-return
	   -msvr4-struct-return -mabi=abi-type -msecure-plt -mbss-plt
	   -mblock-move-inline-limit=num -misel -mno-isel -misel=yes
	   -misel=no -mspe -mno-spe -mspe=yes  -mspe=no -mpaired
	   -mgen-cell-microcode -mwarn-cell-microcode -mvrsave -mno-vrsave
	   -mmulhw -mno-mulhw -mdlmzb -mno-dlmzb -mfloat-gprs=yes
	   -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double -mprototype
	   -mno-prototype -msim	 -mmvme	 -mads	-myellowknife  -memb  -msdata
	   -msdata=opt	-mvxworks  -G num  -pthread -mrecip -mrecip=opt
	   -mno-recip -mrecip-precision -mno-recip-precision -mveclibabi=type
	   -mfriz -mno-friz -mpointers-to-nested-functions
	   -mno-pointers-to-nested-functions -msave-toc-indirect
	   -mno-save-toc-indirect -mpower8-fusion -mno-mpower8-fusion
	   -mpower8-vector -mno-power8-vector -mcrypto -mno-crypto
	   -mdirect-move -mno-direct-move -mquad-memory -mno-quad-memory
	   -mquad-memory-atomic -mno-quad-memory-atomic -mcompat-align-parm
	   -mno-compat-align-parm

	   RX Options -m64bit-doubles  -m32bit-doubles	-fpu  -nofpu -mcpu=
	   -mbig-endian-data -mlittle-endian-data -msmall-data -msim  -mno-sim
	   -mas100-syntax -mno-as100-syntax -mrelax -mmax-constant-size=
	   -mint-register= -mpid -mno-warn-multiple-fast-interrupts
	   -msave-acc-in-interrupts

	   S/390 and zSeries Options -mtune=cpu-type  -march=cpu-type
	   -mhard-float	 -msoft-float  -mhard-dfp -mno-hard-dfp
	   -mlong-double-64 -mlong-double-128 -mbackchain  -mno-backchain
	   -mpacked-stack  -mno-packed-stack -msmall-exec  -mno-small-exec
	   -mmvcle -mno-mvcle -m64  -m31  -mdebug  -mno-debug  -mesa  -mzarch
	   -mtpf-trace -mno-tpf-trace  -mfused-madd  -mno-fused-madd
	   -mwarn-framesize  -mwarn-dynamicstack  -mstack-size -mstack-guard
	   -mhotpatch[=halfwords] -mno-hotpatch

	   Score Options -meb -mel -mnhwloop -muls -mmac -mscore5 -mscore5u
	   -mscore7 -mscore7d

	   SH Options -m1  -m2	-m2e -m2a-nofpu -m2a-single-only -m2a-single
	   -m2a -m3  -m3e -m4-nofpu  -m4-single-only  -m4-single  -m4
	   -m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al -m5-64media
	   -m5-64media-nofpu -m5-32media  -m5-32media-nofpu -m5-compact
	   -m5-compact-nofpu -mb  -ml  -mdalign	 -mrelax -mbigtable -mfmovd
	   -mhitachi -mrenesas -mno-renesas -mnomacsave -mieee -mno-ieee
	   -mbitops  -misize  -minline-ic_invalidate -mpadstruct -mspace
	   -mprefergot	-musermode -multcost=number -mdiv=strategy
	   -mdivsi3_libfunc=name -mfixed-range=register-range
	   -mindexed-addressing -mgettrcost=number -mpt-fixed
	   -maccumulate-outgoing-args -minvalid-symbols -matomic-model=atomic-
	   model -mbranch-cost=num -mzdcbranch -mno-zdcbranch -mcbranchdi
	   -mcmpeqdi -mfused-madd -mno-fused-madd -mfsca -mno-fsca -mfsrra
	   -mno-fsrra -mpretend-cmove -mtas

	   Solaris 2 Options -mimpure-text  -mno-impure-text -pthreads
	   -pthread

	   SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model
	   -mmemory-model=mem-model -m32  -m64	-mapp-regs  -mno-app-regs
	   -mfaster-structs  -mno-faster-structs  -mflat  -mno-flat -mfpu
	   -mno-fpu  -mhard-float  -msoft-float -mhard-quad-float
	   -msoft-quad-float -mstack-bias  -mno-stack-bias -munaligned-doubles
	   -mno-unaligned-doubles -muser-mode  -mno-user-mode -mv8plus
	   -mno-v8plus	-mvis  -mno-vis -mvis2	-mno-vis2  -mvis3  -mno-vis3
	   -mcbcond -mno-cbcond -mfmaf	-mno-fmaf  -mpopc  -mno-popc
	   -mfix-at697f -mfix-ut699

	   SPU Options -mwarn-reloc -merror-reloc -msafe-dma -munsafe-dma
	   -mbranch-hints -msmall-mem -mlarge-mem -mstdmain
	   -mfixed-range=register-range -mea32 -mea64
	   -maddress-space-conversion -mno-address-space-conversion
	   -mcache-size=cache-size -matomic-updates -mno-atomic-updates

	   System V Options -Qy	 -Qn  -YP,paths	 -Ym,dir

	   TILE-Gx Options -mcpu=cpu -m32 -m64 -mcmodel=code-model

	   TILEPro Options -mcpu=cpu -m32

	   V850 Options -mlong-calls  -mno-long-calls  -mep  -mno-ep
	   -mprolog-function  -mno-prolog-function  -mspace -mtda=n  -msda=n
	   -mzda=n -mapp-regs  -mno-app-regs -mdisable-callt
	   -mno-disable-callt -mv850e2v3 -mv850e2 -mv850e1 -mv850es -mv850e
	   -mv850 -mv850e3v5 -mloop -mrelax -mlong-jumps -msoft-float
	   -mhard-float -mgcc-abi -mrh850-abi -mbig-switch

	   VAX Options -mg  -mgnu  -munix

	   VMS Options -mvms-return-codes -mdebug-main=prefix -mmalloc64
	   -mpointer-size=size

	   VxWorks Options -mrtp  -non-static  -Bstatic	 -Bdynamic -Xbind-lazy
	   -Xbind-now

	   x86-64 Options See i386 and x86-64 Options.

	   Xstormy16 Options -msim

	   Xtensa Options -mconst16 -mno-const16 -mfused-madd  -mno-fused-madd
	   -mforce-no-pic -mserialize-volatile	-mno-serialize-volatile
	   -mtext-section-literals  -mno-text-section-literals -mtarget-align
	   -mno-target-align -mlongcalls  -mno-longcalls

	   zSeries Options See S/390 and zSeries Options.

       Code Generation Options
	   -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions
	   -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables
	   -fasynchronous-unwind-tables -fno-gnu-unique
	   -finhibit-size-directive  -finstrument-functions
	   -finstrument-functions-exclude-function-list=sym,sym,...
	   -finstrument-functions-exclude-file-list=file,file,...  -fno-common
	   -fno-ident -fpcc-struct-return  -fpic  -fPIC -fpie -fPIE
	   -fno-jump-tables -frecord-gcc-switches -freg-struct-return
	   -fshort-enums -fshort-double	 -fshort-wchar -fverbose-asm
	   -fpack-struct[=n]  -fstack-check -fstack-limit-register=reg
	   -fstack-limit-symbol=sym -fno-stack-limit -fsplit-stack
	   -fleading-underscore	 -ftls-model=model -fstack-reuse=reuse_level
	   -ftrapv  -fwrapv  -fbounds-check -fvisibility
	   -fstrict-volatile-bitfields -fsync-libcalls

   Options Controlling the Kind of Output
       Compilation can involve up to four stages: preprocessing, compilation
       proper, assembly and linking, always in that order.  GCC is capable of
       preprocessing and compiling several files either into several assembler
       input files, or into one assembler input file; then each assembler
       input file produces an object file, and linking combines all the object
       files (those newly compiled, and those specified as input) into an
       executable file.

       For any given input file, the file name suffix determines what kind of
       compilation is done:

       file.c
	   C source code that must be preprocessed.

       file.i
	   C source code that should not be preprocessed.

       file.ii
	   C++ source code that should not be preprocessed.

       file.m
	   Objective-C source code.  Note that you must link with the libobjc
	   library to make an Objective-C program work.

       file.mi
	   Objective-C source code that should not be preprocessed.

       file.mm
       file.M
	   Objective-C++ source code.  Note that you must link with the
	   libobjc library to make an Objective-C++ program work.  Note that
	   .M refers to a literal capital M.

       file.mii
	   Objective-C++ source code that should not be preprocessed.

       file.h
	   C, C++, Objective-C or Objective-C++ header file to be turned into
	   a precompiled header (default), or C, C++ header file to be turned
	   into an Ada spec (via the -fdump-ada-spec switch).

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
	   C++ source code that must be preprocessed.  Note that in .cxx, the
	   last two letters must both be literally x.  Likewise, .C refers to
	   a literal capital C.

       file.mm
       file.M
	   Objective-C++ source code that must be preprocessed.

       file.mii
	   Objective-C++ source code that should not be preprocessed.

       file.hh
       file.H
       file.hp
       file.hxx
       file.hpp
       file.HPP
       file.h++
       file.tcc
	   C++ header file to be turned into a precompiled header or Ada spec.

       file.f
       file.for
       file.ftn
	   Fixed form Fortran source code that should not be preprocessed.

       file.F
       file.FOR
       file.fpp
       file.FPP
       file.FTN
	   Fixed form Fortran source code that must be preprocessed (with the
	   traditional preprocessor).

       file.f90
       file.f95
       file.f03
       file.f08
	   Free form Fortran source code that should not be preprocessed.

       file.F90
       file.F95
       file.F03
       file.F08
	   Free form Fortran source code that must be preprocessed (with the
	   traditional preprocessor).

       file.go
	   Go source code.

       file.ads
	   Ada source code file that contains a library unit declaration (a
	   declaration of a package, subprogram, or generic, or a generic
	   instantiation), or a library unit renaming declaration (a package,
	   generic, or subprogram renaming declaration).  Such files are also
	   called specs.

       file.adb
	   Ada source code file containing a library unit body (a subprogram
	   or package body).  Such files are also called bodies.

       file.s
	   Assembler code.

       file.S
       file.sx
	   Assembler code that must be preprocessed.

       other
	   An object file to be fed straight into linking.  Any file name with
	   no recognized suffix is treated this way.

       You can specify the input language explicitly with the -x option:

       -x language
	   Specify explicitly the language for the following input files
	   (rather than letting the compiler choose a default based on the
	   file name suffix).  This option applies to all following input
	   files until the next -x option.  Possible values for language are:

		   c  c-header	cpp-output
		   c++	c++-header  c++-cpp-output
		   objective-c	objective-c-header  objective-c-cpp-output
		   objective-c++ objective-c++-header objective-c++-cpp-output
		   assembler  assembler-with-cpp
		   ada
		   f77	f77-cpp-input f95  f95-cpp-input
		   go
		   java

       -x none
	   Turn off any specification of a language, so that subsequent files
	   are handled according to their file name suffixes (as they are if
	   -x has not been used at all).

       -pass-exit-codes
	   Normally the gcc program exits with the code of 1 if any phase of
	   the compiler returns a non-success return code.  If you specify
	   -pass-exit-codes, the gcc program instead returns with the
	   numerically highest error produced by any phase returning an error
	   indication.	The C, C++, and Fortran front ends return 4 if an
	   internal compiler error is encountered.

       If you only want some of the stages of compilation, you can use -x (or
       filename suffixes) to tell gcc where to start, and one of the options
       -c, -S, or -E to say where gcc is to stop.  Note that some combinations
       (for example, -x cpp-output -E) instruct gcc to do nothing at all.

       -c  Compile or assemble the source files, but do not link.  The linking
	   stage simply is not done.  The ultimate output is in the form of an
	   object file for each source file.

	   By default, the object file name for a source file is made by
	   replacing the suffix .c, .i, .s, etc., with .o.

	   Unrecognized input files, not requiring compilation or assembly,
	   are ignored.

       -S  Stop after the stage of compilation proper; do not assemble.	 The
	   output is in the form of an assembler code file for each non-
	   assembler input file specified.

	   By default, the assembler file name for a source file is made by
	   replacing the suffix .c, .i, etc., with .s.

	   Input files that don't require compilation are ignored.

       -E  Stop after the preprocessing stage; do not run the compiler proper.
	   The output is in the form of preprocessed source code, which is
	   sent to the standard output.

	   Input files that don't require preprocessing are ignored.

       -o file
	   Place output in file file.  This applies to whatever sort of output
	   is being produced, whether it be an executable file, an object
	   file, an assembler file or preprocessed C code.

	   If -o is not specified, the default is to put an executable file in
	   a.out, the object file for source.suffix in source.o, its assembler
	   file in source.s, a precompiled header file in source.suffix.gch,
	   and all preprocessed C source on standard output.

       -v  Print (on standard error output) the commands executed to run the
	   stages of compilation.  Also print the version number of the
	   compiler driver program and of the preprocessor and the compiler
	   proper.

       -###
	   Like -v except the commands are not executed and arguments are
	   quoted unless they contain only alphanumeric characters or "./-_".
	   This is useful for shell scripts to capture the driver-generated
	   command lines.

       -pipe
	   Use pipes rather than temporary files for communication between the
	   various stages of compilation.  This fails to work on some systems
	   where the assembler is unable to read from a pipe; but the GNU
	   assembler has no trouble.

       --help
	   Print (on the standard output) a description of the command-line
	   options understood by gcc.  If the -v option is also specified then
	   --help is also passed on to the various processes invoked by gcc,
	   so that they can display the command-line options they accept.  If
	   the -Wextra option has also been specified (prior to the --help
	   option), then command-line options that have no documentation
	   associated with them are also displayed.

       --target-help
	   Print (on the standard output) a description of target-specific
	   command-line options for each tool.	For some targets extra target-
	   specific information may also be printed.

       --help={class|[^]qualifier}[,...]
	   Print (on the standard output) a description of the command-line
	   options understood by the compiler that fit into all specified
	   classes and qualifiers.  These are the supported classes:

	   optimizers
	       Display all of the optimization options supported by the
	       compiler.

	   warnings
	       Display all of the options controlling warning messages
	       produced by the compiler.

	   target
	       Display target-specific options.	 Unlike the --target-help
	       option however, target-specific options of the linker and
	       assembler are not displayed.  This is because those tools do
	       not currently support the extended --help= syntax.

	   params
	       Display the values recognized by the --param option.

	   language
	       Display the options supported for language, where language is
	       the name of one of the languages supported in this version of
	       GCC.

	   common
	       Display the options that are common to all languages.

	   These are the supported qualifiers:

	   undocumented
	       Display only those options that are undocumented.

	   joined
	       Display options taking an argument that appears after an equal
	       sign in the same continuous piece of text, such as:
	       --help=target.

	   separate
	       Display options taking an argument that appears as a separate
	       word following the original option, such as: -o output-file.

	   Thus for example to display all the undocumented target-specific
	   switches supported by the compiler, use:

		   --help=target,undocumented

	   The sense of a qualifier can be inverted by prefixing it with the ^
	   character, so for example to display all binary warning options
	   (i.e., ones that are either on or off and that do not take an
	   argument) that have a description, use:

		   --help=warnings,^joined,^undocumented

	   The argument to --help= should not consist solely of inverted
	   qualifiers.

	   Combining several classes is possible, although this usually
	   restricts the output so much that there is nothing to display.  One
	   case where it does work, however, is when one of the classes is
	   target.  For example, to display all the target-specific
	   optimization options, use:

		   --help=target,optimizers

	   The --help= option can be repeated on the command line.  Each
	   successive use displays its requested class of options, skipping
	   those that have already been displayed.

	   If the -Q option appears on the command line before the --help=
	   option, then the descriptive text displayed by --help= is changed.
	   Instead of describing the displayed options, an indication is given
	   as to whether the option is enabled, disabled or set to a specific
	   value (assuming that the compiler knows this at the point where the
	   --help= option is used).

	   Here is a truncated example from the ARM port of gcc:

		     % gcc -Q -mabi=2 --help=target -c
		     The following options are target specific:
		     -mabi=				   2
		     -mabort-on-noreturn		   [disabled]
		     -mapcs				   [disabled]

	   The output is sensitive to the effects of previous command-line
	   options, so for example it is possible to find out which
	   optimizations are enabled at -O2 by using:

		   -Q -O2 --help=optimizers

	   Alternatively you can discover which binary optimizations are
	   enabled by -O3 by using:

		   gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
		   gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
		   diff /tmp/O2-opts /tmp/O3-opts | grep enabled

       -no-canonical-prefixes
	   Do not expand any symbolic links, resolve references to /../ or
	   /./, or make the path absolute when generating a relative prefix.

       --version
	   Display the version number and copyrights of the invoked GCC.

       -wrapper
	   Invoke all subcommands under a wrapper program.  The name of the
	   wrapper program and its parameters are passed as a comma separated
	   list.

		   gcc -c t.c -wrapper gdb,--args

	   This invokes all subprograms of gcc under gdb --args, thus the
	   invocation of cc1 is gdb --args cc1 ....

       -fplugin=name.so
	   Load the plugin code in file name.so, assumed to be a shared object
	   to be dlopen'd by the compiler.  The base name of the shared object
	   file is used to identify the plugin for the purposes of argument
	   parsing (See -fplugin-arg-name-key=value below).  Each plugin
	   should define the callback functions specified in the Plugins API.

       -fplugin-arg-name-key=value
	   Define an argument called key with a value of value for the plugin
	   called name.

       -fdump-ada-spec[-slim]
	   For C and C++ source and include files, generate corresponding Ada
	   specs.

       -fada-spec-parent=unit
	   In conjunction with -fdump-ada-spec[-slim] above, generate Ada
	   specs as child units of parent unit.

       -fdump-go-spec=file
	   For input files in any language, generate corresponding Go
	   declarations in file.  This generates Go "const", "type", "var",
	   and "func" declarations which may be a useful way to start writing
	   a Go interface to code written in some other language.

       @file
	   Read command-line options from file.	 The options read are inserted
	   in place of the original @file option.  If file does not exist, or
	   cannot be read, then the option will be treated literally, and not
	   removed.

	   Options in file are separated by whitespace.	 A whitespace
	   character may be included in an option by surrounding the entire
	   option in either single or double quotes.  Any character (including
	   a backslash) may be included by prefixing the character to be
	   included with a backslash.  The file may itself contain additional
	   @file options; any such options will be processed recursively.

   Compiling C++ Programs
       C++ source files conventionally use one of the suffixes .C, .cc, .cpp,
       .CPP, .c++, .cp, or .cxx; C++ header files often use .hh, .hpp, .H, or
       (for shared template code) .tcc; and preprocessed C++ files use the
       suffix .ii.  GCC recognizes files with these names and compiles them as
       C++ programs even if you call the compiler the same way as for
       compiling C programs (usually with the name gcc).

       However, the use of gcc does not add the C++ library.  g++ is a program
       that calls GCC and automatically specifies linking against the C++
       library.	 It treats .c, .h and .i files as C++ source files instead of
       C source files unless -x is used.  This program is also useful when
       precompiling a C header file with a .h extension for use in C++
       compilations.  On many systems, g++ is also installed with the name
       c++.

       When you compile C++ programs, you may specify many of the same
       command-line options that you use for compiling programs in any
       language; or command-line options meaningful for C and related
       languages; or options that are meaningful only for C++ programs.

   Options Controlling C Dialect
       The following options control the dialect of C (or languages derived
       from C, such as C++, Objective-C and Objective-C++) that the compiler
       accepts:

       -ansi
	   In C mode, this is equivalent to -std=c90. In C++ mode, it is
	   equivalent to -std=c++98.

	   This turns off certain features of GCC that are incompatible with
	   ISO C90 (when compiling C code), or of standard C++ (when compiling
	   C++ code), such as the "asm" and "typeof" keywords, and predefined
	   macros such as "unix" and "vax" that identify the type of system
	   you are using.  It also enables the undesirable and rarely used ISO
	   trigraph feature.  For the C compiler, it disables recognition of
	   C++ style // comments as well as the "inline" keyword.

	   The alternate keywords "__asm__", "__extension__", "__inline__" and
	   "__typeof__" continue to work despite -ansi.	 You would not want to
	   use them in an ISO C program, of course, but it is useful to put
	   them in header files that might be included in compilations done
	   with -ansi.	Alternate predefined macros such as "__unix__" and
	   "__vax__" are also available, with or without -ansi.

	   The -ansi option does not cause non-ISO programs to be rejected
	   gratuitously.  For that, -Wpedantic is required in addition to
	   -ansi.

	   The macro "__STRICT_ANSI__" is predefined when the -ansi option is
	   used.  Some header files may notice this macro and refrain from
	   declaring certain functions or defining certain macros that the ISO
	   standard doesn't call for; this is to avoid interfering with any
	   programs that might use these names for other things.

	   Functions that are normally built in but do not have semantics
	   defined by ISO C (such as "alloca" and "ffs") are not built-in
	   functions when -ansi is used.

       -std=
	   Determine the language standard.   This option is currently only
	   supported when compiling C or C++.

	   The compiler can accept several base standards, such as c90 or
	   c++98, and GNU dialects of those standards, such as gnu90 or
	   gnu++98.  When a base standard is specified, the compiler accepts
	   all programs following that standard plus those using GNU
	   extensions that do not contradict it.  For example, -std=c90 turns
	   off certain features of GCC that are incompatible with ISO C90,
	   such as the "asm" and "typeof" keywords, but not other GNU
	   extensions that do not have a meaning in ISO C90, such as omitting
	   the middle term of a "?:" expression. On the other hand, when a GNU
	   dialect of a standard is specified, all features supported by the
	   compiler are enabled, even when those features change the meaning
	   of the base standard.  As a result, some strict-conforming programs
	   may be rejected.  The particular standard is used by -Wpedantic to
	   identify which features are GNU extensions given that version of
	   the standard. For example -std=gnu90 -Wpedantic warns about C++
	   style // comments, while -std=gnu99 -Wpedantic does not.

	   A value for this option must be provided; possible values are

	   c90
	   c89
	   iso9899:1990
	       Support all ISO C90 programs (certain GNU extensions that
	       conflict with ISO C90 are disabled). Same as -ansi for C code.

	   iso9899:199409
	       ISO C90 as modified in amendment 1.

	   c99
	   c9x
	   iso9899:1999
	   iso9899:199x
	       ISO C99.	 Note that this standard is not yet fully supported;
	       see <http://gcc.gnu.org/c99status.html> for more information.
	       The names c9x and iso9899:199x are deprecated.

	   c11
	   c1x
	   iso9899:2011
	       ISO C11, the 2011 revision of the ISO C standard.  Support is
	       incomplete and experimental.  The name c1x is deprecated.

	   gnu90
	   gnu89
	       GNU dialect of ISO C90 (including some C99 features). This is
	       the default for C code.

	   gnu99
	   gnu9x
	       GNU dialect of ISO C99.	When ISO C99 is fully implemented in
	       GCC, this will become the default.  The name gnu9x is
	       deprecated.

	   gnu11
	   gnu1x
	       GNU dialect of ISO C11.	Support is incomplete and
	       experimental.  The name gnu1x is deprecated.

	   c++98
	   c++03
	       The 1998 ISO C++ standard plus the 2003 technical corrigendum
	       and some additional defect reports. Same as -ansi for C++ code.

	   gnu++98
	   gnu++03
	       GNU dialect of -std=c++98.  This is the default for C++ code.

	   c++11
	   c++0x
	       The 2011 ISO C++ standard plus amendments.  Support for C++11
	       is still experimental, and may change in incompatible ways in
	       future releases.	 The name c++0x is deprecated.

	   gnu++11
	   gnu++0x
	       GNU dialect of -std=c++11. Support for C++11 is still
	       experimental, and may change in incompatible ways in future
	       releases.  The name gnu++0x is deprecated.

	   c++1y
	       The next revision of the ISO C++ standard, tentatively planned
	       for 2017.  Support is highly experimental, and will almost
	       certainly change in incompatible ways in future releases.

	   gnu++1y
	       GNU dialect of -std=c++1y.  Support is highly experimental, and
	       will almost certainly change in incompatible ways in future
	       releases.

       -fgnu89-inline
	   The option -fgnu89-inline tells GCC to use the traditional GNU
	   semantics for "inline" functions when in C99 mode.
	     This option is accepted and ignored by GCC versions 4.1.3 up to
	   but not including 4.3.  In GCC versions 4.3 and later it changes
	   the behavior of GCC in C99 mode.  Using this option is roughly
	   equivalent to adding the "gnu_inline" function attribute to all
	   inline functions.

	   The option -fno-gnu89-inline explicitly tells GCC to use the C99
	   semantics for "inline" when in C99 or gnu99 mode (i.e., it
	   specifies the default behavior).  This option was first supported
	   in GCC 4.3.	This option is not supported in -std=c90 or -std=gnu90
	   mode.

	   The preprocessor macros "__GNUC_GNU_INLINE__" and
	   "__GNUC_STDC_INLINE__" may be used to check which semantics are in
	   effect for "inline" functions.

       -aux-info filename
	   Output to the given filename prototyped declarations for all
	   functions declared and/or defined in a translation unit, including
	   those in header files.  This option is silently ignored in any
	   language other than C.

	   Besides declarations, the file indicates, in comments, the origin
	   of each declaration (source file and line), whether the declaration
	   was implicit, prototyped or unprototyped (I, N for new or O for
	   old, respectively, in the first character after the line number and
	   the colon), and whether it came from a declaration or a definition
	   (C or F, respectively, in the following character).	In the case of
	   function definitions, a K&R-style list of arguments followed by
	   their declarations is also provided, inside comments, after the
	   declaration.

       -fallow-parameterless-variadic-functions
	   Accept variadic functions without named parameters.

	   Although it is possible to define such a function, this is not very
	   useful as it is not possible to read the arguments.	This is only
	   supported for C as this construct is allowed by C++.

       -fno-asm
	   Do not recognize "asm", "inline" or "typeof" as a keyword, so that
	   code can use these words as identifiers.  You can use the keywords
	   "__asm__", "__inline__" and "__typeof__" instead.  -ansi implies
	   -fno-asm.

	   In C++, this switch only affects the "typeof" keyword, since "asm"
	   and "inline" are standard keywords.	You may want to use the
	   -fno-gnu-keywords flag instead, which has the same effect.  In C99
	   mode (-std=c99 or -std=gnu99), this switch only affects the "asm"
	   and "typeof" keywords, since "inline" is a standard keyword in ISO
	   C99.

       -fno-builtin
       -fno-builtin-function
	   Don't recognize built-in functions that do not begin with
	   __builtin_ as prefix.

	   GCC normally generates special code to handle certain built-in
	   functions more efficiently; for instance, calls to "alloca" may
	   become single instructions which adjust the stack directly, and
	   calls to "memcpy" may become inline copy loops.  The resulting code
	   is often both smaller and faster, but since the function calls no
	   longer appear as such, you cannot set a breakpoint on those calls,
	   nor can you change the behavior of the functions by linking with a
	   different library.  In addition, when a function is recognized as a
	   built-in function, GCC may use information about that function to
	   warn about problems with calls to that function, or to generate
	   more efficient code, even if the resulting code still contains
	   calls to that function.  For example, warnings are given with
	   -Wformat for bad calls to "printf" when "printf" is built in and
	   "strlen" is known not to modify global memory.

	   With the -fno-builtin-function option only the built-in function
	   function is disabled.  function must not begin with __builtin_.  If
	   a function is named that is not built-in in this version of GCC,
	   this option is ignored.  There is no corresponding
	   -fbuiltin-function option; if you wish to enable built-in functions
	   selectively when using -fno-builtin or -ffreestanding, you may
	   define macros such as:

		   #define abs(n)	   __builtin_abs ((n))
		   #define strcpy(d, s)	   __builtin_strcpy ((d), (s))

       -fhosted
	   Assert that compilation targets a hosted environment.  This implies
	   -fbuiltin.  A hosted environment is one in which the entire
	   standard library is available, and in which "main" has a return
	   type of "int".  Examples are nearly everything except a kernel.
	   This is equivalent to -fno-freestanding.

       -ffreestanding
	   Assert that compilation targets a freestanding environment.	This
	   implies -fno-builtin.  A freestanding environment is one in which
	   the standard library may not exist, and program startup may not
	   necessarily be at "main".  The most obvious example is an OS
	   kernel.  This is equivalent to -fno-hosted.

       -fopenmp
	   Enable handling of OpenMP directives "#pragma omp" in C/C++ and
	   "!$omp" in Fortran.	When -fopenmp is specified, the compiler
	   generates parallel code according to the OpenMP Application Program
	   Interface v3.0 <http://www.openmp.org/>.  This option implies
	   -pthread, and thus is only supported on targets that have support
	   for -pthread.

       -fgnu-tm
	   When the option -fgnu-tm is specified, the compiler generates code
	   for the Linux variant of Intel's current Transactional Memory ABI
	   specification document (Revision 1.1, May 6 2009).  This is an
	   experimental feature whose interface may change in future versions
	   of GCC, as the official specification changes.  Please note that
	   not all architectures are supported for this feature.

	   For more information on GCC's support for transactional memory,

	   Note that the transactional memory feature is not supported with
	   non-call exceptions (-fnon-call-exceptions).

       -fms-extensions
	   Accept some non-standard constructs used in Microsoft header files.

	   In C++ code, this allows member names in structures to be similar
	   to previous types declarations.

		   typedef int UOW;
		   struct ABC {
		     UOW UOW;
		   };

	   Some cases of unnamed fields in structures and unions are only
	   accepted with this option.

       -fplan9-extensions
	   Accept some non-standard constructs used in Plan 9 code.

	   This enables -fms-extensions, permits passing pointers to
	   structures with anonymous fields to functions that expect pointers
	   to elements of the type of the field, and permits referring to
	   anonymous fields declared using a typedef.	 This is only
	   supported for C, not C++.

       -trigraphs
	   Support ISO C trigraphs.  The -ansi option (and -std options for
	   strict ISO C conformance) implies -trigraphs.

       -traditional
       -traditional-cpp
	   Formerly, these options caused GCC to attempt to emulate a pre-
	   standard C compiler.	 They are now only supported with the -E
	   switch.  The preprocessor continues to support a pre-standard mode.
	   See the GNU CPP manual for details.

       -fcond-mismatch
	   Allow conditional expressions with mismatched types in the second
	   and third arguments.	 The value of such an expression is void.
	   This option is not supported for C++.

       -flax-vector-conversions
	   Allow implicit conversions between vectors with differing numbers
	   of elements and/or incompatible element types.  This option should
	   not be used for new code.

       -funsigned-char
	   Let the type "char" be unsigned, like "unsigned char".

	   Each kind of machine has a default for what "char" should be.  It
	   is either like "unsigned char" by default or like "signed char" by
	   default.

	   Ideally, a portable program should always use "signed char" or
	   "unsigned char" when it depends on the signedness of an object.
	   But many programs have been written to use plain "char" and expect
	   it to be signed, or expect it to be unsigned, depending on the
	   machines they were written for.  This option, and its inverse, let
	   you make such a program work with the opposite default.

	   The type "char" is always a distinct type from each of "signed
	   char" or "unsigned char", even though its behavior is always just
	   like one of those two.

       -fsigned-char
	   Let the type "char" be signed, like "signed char".

	   Note that this is equivalent to -fno-unsigned-char, which is the
	   negative form of -funsigned-char.  Likewise, the option
	   -fno-signed-char is equivalent to -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
	   These options control whether a bit-field is signed or unsigned,
	   when the declaration does not use either "signed" or "unsigned".
	   By default, such a bit-field is signed, because this is consistent:
	   the basic integer types such as "int" are signed types.

   Options Controlling C++ Dialect
       This section describes the command-line options that are only
       meaningful for C++ programs.  You can also use most of the GNU compiler
       options regardless of what language your program is in.	For example,
       you might compile a file "firstClass.C" like this:

	       g++ -g -frepo -O -c firstClass.C

       In this example, only -frepo is an option meant only for C++ programs;
       you can use the other options with any language supported by GCC.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
	   Use version n of the C++ ABI.  The default is version 2.

	   Version 0 refers to the version conforming most closely to the C++
	   ABI specification.  Therefore, the ABI obtained using version 0
	   will change in different versions of G++ as ABI bugs are fixed.

	   Version 1 is the version of the C++ ABI that first appeared in G++
	   3.2.

	   Version 2 is the version of the C++ ABI that first appeared in G++
	   3.4.

	   Version 3 corrects an error in mangling a constant address as a
	   template argument.

	   Version 4, which first appeared in G++ 4.5, implements a standard
	   mangling for vector types.

	   Version 5, which first appeared in G++ 4.6, corrects the mangling
	   of attribute const/volatile on function pointer types, decltype of
	   a plain decl, and use of a function parameter in the declaration of
	   another parameter.

	   Version 6, which first appeared in G++ 4.7, corrects the promotion
	   behavior of C++11 scoped enums and the mangling of template
	   argument packs, const/static_cast, prefix ++ and --, and a class
	   scope function used as a template argument.

	   See also -Wabi.

       -fno-access-control
	   Turn off all access checking.  This switch is mainly useful for
	   working around bugs in the access control code.

       -fcheck-new
	   Check that the pointer returned by "operator new" is non-null
	   before attempting to modify the storage allocated.  This check is
	   normally unnecessary because the C++ standard specifies that
	   "operator new" only returns 0 if it is declared throw(), in which
	   case the compiler always checks the return value even without this
	   option.  In all other cases, when "operator new" has a non-empty
	   exception specification, memory exhaustion is signalled by throwing
	   "std::bad_alloc".  See also new (nothrow).

       -fconstexpr-depth=n
	   Set the maximum nested evaluation depth for C++11 constexpr
	   functions to n.  A limit is needed to detect endless recursion
	   during constant expression evaluation.  The minimum specified by
	   the standard is 512.

       -fdeduce-init-list
	   Enable deduction of a template type parameter as
	   "std::initializer_list" from a brace-enclosed initializer list,
	   i.e.

		   template <class T> auto forward(T t) -> decltype (realfn (t))
		   {
		     return realfn (t);
		   }

		   void f()
		   {
		     forward({1,2}); // call forward<std::initializer_list<int>>
		   }

	   This deduction was implemented as a possible extension to the
	   originally proposed semantics for the C++11 standard, but was not
	   part of the final standard, so it is disabled by default.  This
	   option is deprecated, and may be removed in a future version of
	   G++.

       -ffriend-injection
	   Inject friend functions into the enclosing namespace, so that they
	   are visible outside the scope of the class in which they are
	   declared.  Friend functions were documented to work this way in the
	   old Annotated C++ Reference Manual, and versions of G++ before 4.1
	   always worked that way.  However, in ISO C++ a friend function that
	   is not declared in an enclosing scope can only be found using
	   argument dependent lookup.  This option causes friends to be
	   injected as they were in earlier releases.

	   This option is for compatibility, and may be removed in a future
	   release of G++.

       -fno-elide-constructors
	   The C++ standard allows an implementation to omit creating a
	   temporary that is only used to initialize another object of the
	   same type.  Specifying this option disables that optimization, and
	   forces G++ to call the copy constructor in all cases.

       -fno-enforce-eh-specs
	   Don't generate code to check for violation of exception
	   specifications at run time.	This option violates the C++ standard,
	   but may be useful for reducing code size in production builds, much
	   like defining NDEBUG.  This does not give user code permission to
	   throw exceptions in violation of the exception specifications; the
	   compiler still optimizes based on the specifications, so throwing
	   an unexpected exception results in undefined behavior at run time.

       -fextern-tls-init
       -fno-extern-tls-init
	   The C++11 and OpenMP standards allow thread_local and threadprivate
	   variables to have dynamic (runtime) initialization.	To support
	   this, any use of such a variable goes through a wrapper function
	   that performs any necessary initialization.	When the use and
	   definition of the variable are in the same translation unit, this
	   overhead can be optimized away, but when the use is in a different
	   translation unit there is significant overhead even if the variable
	   doesn't actually need dynamic initialization.  If the programmer
	   can be sure that no use of the variable in a non-defining TU needs
	   to trigger dynamic initialization (either because the variable is
	   statically initialized, or a use of the variable in the defining TU
	   will be executed before any uses in another TU), they can avoid
	   this overhead with the -fno-extern-tls-init option.

	   On targets that support symbol aliases, the default is
	   -fextern-tls-init.  On targets that do not support symbol aliases,
	   the default is -fno-extern-tls-init.

       -ffor-scope
       -fno-for-scope
	   If -ffor-scope is specified, the scope of variables declared in a
	   for-init-statement is limited to the for loop itself, as specified
	   by the C++ standard.	 If -fno-for-scope is specified, the scope of
	   variables declared in a for-init-statement extends to the end of
	   the enclosing scope, as was the case in old versions of G++, and
	   other (traditional) implementations of C++.

	   If neither flag is given, the default is to follow the standard,
	   but to allow and give a warning for old-style code that would
	   otherwise be invalid, or have different behavior.

       -fno-gnu-keywords
	   Do not recognize "typeof" as a keyword, so that code can use this
	   word as an identifier.  You can use the keyword "__typeof__"
	   instead.  -ansi implies -fno-gnu-keywords.

       -fno-implicit-templates
	   Never emit code for non-inline templates that are instantiated
	   implicitly (i.e. by use); only emit code for explicit
	   instantiations.

       -fno-implicit-inline-templates
	   Don't emit code for implicit instantiations of inline templates,
	   either.  The default is to handle inlines differently so that
	   compiles with and without optimization need the same set of
	   explicit instantiations.

       -fno-implement-inlines
	   To save space, do not emit out-of-line copies of inline functions
	   controlled by #pragma implementation.  This causes linker errors if
	   these functions are not inlined everywhere they are called.

       -fms-extensions
	   Disable Wpedantic warnings about constructs used in MFC, such as
	   implicit int and getting a pointer to member function via non-
	   standard syntax.

       -fno-nonansi-builtins
	   Disable built-in declarations of functions that are not mandated by
	   ANSI/ISO C.	These include "ffs", "alloca", "_exit", "index",
	   "bzero", "conjf", and other related functions.

       -fnothrow-opt
	   Treat a "throw()" exception specification as if it were a
	   "noexcept" specification to reduce or eliminate the text size
	   overhead relative to a function with no exception specification.
	   If the function has local variables of types with non-trivial
	   destructors, the exception specification actually makes the
	   function smaller because the EH cleanups for those variables can be
	   optimized away.  The semantic effect is that an exception thrown
	   out of a function with such an exception specification results in a
	   call to "terminate" rather than "unexpected".

       -fno-operator-names
	   Do not treat the operator name keywords "and", "bitand", "bitor",
	   "compl", "not", "or" and "xor" as synonyms as keywords.

       -fno-optional-diags
	   Disable diagnostics that the standard says a compiler does not need
	   to issue.  Currently, the only such diagnostic issued by G++ is the
	   one for a name having multiple meanings within a class.

       -fpermissive
	   Downgrade some diagnostics about nonconformant code from errors to
	   warnings.  Thus, using -fpermissive allows some nonconforming code
	   to compile.

       -fno-pretty-templates
	   When an error message refers to a specialization of a function
	   template, the compiler normally prints the signature of the
	   template followed by the template arguments and any typedefs or
	   typenames in the signature (e.g. "void f(T) [with T = int]" rather
	   than "void f(int)") so that it's clear which template is involved.
	   When an error message refers to a specialization of a class
	   template, the compiler omits any template arguments that match the
	   default template arguments for that template.  If either of these
	   behaviors make it harder to understand the error message rather
	   than easier, you can use -fno-pretty-templates to disable them.

       -frepo
	   Enable automatic template instantiation at link time.  This option
	   also implies -fno-implicit-templates.

       -fno-rtti
	   Disable generation of information about every class with virtual
	   functions for use by the C++ run-time type identification features
	   (dynamic_cast and typeid).  If you don't use those parts of the
	   language, you can save some space by using this flag.  Note that
	   exception handling uses the same information, but G++ generates it
	   as needed. The dynamic_cast operator can still be used for casts
	   that do not require run-time type information, i.e. casts to "void
	   *" or to unambiguous base classes.

       -fstats
	   Emit statistics about front-end processing at the end of the
	   compilation.	 This information is generally only useful to the G++
	   development team.

       -fstrict-enums
	   Allow the compiler to optimize using the assumption that a value of
	   enumerated type can only be one of the values of the enumeration
	   (as defined in the C++ standard; basically, a value that can be
	   represented in the minimum number of bits needed to represent all
	   the enumerators).  This assumption may not be valid if the program
	   uses a cast to convert an arbitrary integer value to the enumerated
	   type.

       -ftemplate-backtrace-limit=n
	   Set the maximum number of template instantiation notes for a single
	   warning or error to n.  The default value is 10.

       -ftemplate-depth=n
	   Set the maximum instantiation depth for template classes to n.  A
	   limit on the template instantiation depth is needed to detect
	   endless recursions during template class instantiation.  ANSI/ISO
	   C++ conforming programs must not rely on a maximum depth greater
	   than 17 (changed to 1024 in C++11).	The default value is 900, as
	   the compiler can run out of stack space before hitting 1024 in some
	   situations.

       -fno-threadsafe-statics
	   Do not emit the extra code to use the routines specified in the C++
	   ABI for thread-safe initialization of local statics.	 You can use
	   this option to reduce code size slightly in code that doesn't need
	   to be thread-safe.

       -fuse-cxa-atexit
	   Register destructors for objects with static storage duration with
	   the "__cxa_atexit" function rather than the "atexit" function.
	   This option is required for fully standards-compliant handling of
	   static destructors, but only works if your C library supports
	   "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
	   Don't use the "__cxa_get_exception_ptr" runtime routine.  This
	   causes "std::uncaught_exception" to be incorrect, but is necessary
	   if the runtime routine is not available.

       -fvisibility-inlines-hidden
	   This switch declares that the user does not attempt to compare
	   pointers to inline functions or methods where the addresses of the
	   two functions are taken in different shared objects.

	   The effect of this is that GCC may, effectively, mark inline
	   methods with "__attribute__ ((visibility ("hidden")))" so that they
	   do not appear in the export table of a DSO and do not require a PLT
	   indirection when used within the DSO.  Enabling this option can
	   have a dramatic effect on load and link times of a DSO as it
	   massively reduces the size of the dynamic export table when the
	   library makes heavy use of templates.

	   The behavior of this switch is not quite the same as marking the
	   methods as hidden directly, because it does not affect static
	   variables local to the function or cause the compiler to deduce
	   that the function is defined in only one shared object.

	   You may mark a method as having a visibility explicitly to negate
	   the effect of the switch for that method.  For example, if you do
	   want to compare pointers to a particular inline method, you might
	   mark it as having default visibility.  Marking the enclosing class
	   with explicit visibility has no effect.

	   Explicitly instantiated inline methods are unaffected by this
	   option as their linkage might otherwise cross a shared library
	   boundary.

       -fvisibility-ms-compat
	   This flag attempts to use visibility settings to make GCC's C++
	   linkage model compatible with that of Microsoft Visual Studio.

	   The flag makes these changes to GCC's linkage model:

	   1.  It sets the default visibility to "hidden", like
	       -fvisibility=hidden.

	   2.  Types, but not their members, are not hidden by default.

	   3.  The One Definition Rule is relaxed for types without explicit
	       visibility specifications that are defined in more than one
	       shared object: those declarations are permitted if they are
	       permitted when this option is not used.

	   In new code it is better to use -fvisibility=hidden and export
	   those classes that are intended to be externally visible.
	   Unfortunately it is possible for code to rely, perhaps
	   accidentally, on the Visual Studio behavior.

	   Among the consequences of these changes are that static data
	   members of the same type with the same name but defined in
	   different shared objects are different, so changing one does not
	   change the other; and that pointers to function members defined in
	   different shared objects may not compare equal.  When this flag is
	   given, it is a violation of the ODR to define types with the same
	   name differently.

       -fno-weak
	   Do not use weak symbol support, even if it is provided by the
	   linker.  By default, G++ uses weak symbols if they are available.
	   This option exists only for testing, and should not be used by end-
	   users; it results in inferior code and has no benefits.  This
	   option may be removed in a future release of G++.

       -nostdinc++
	   Do not search for header files in the standard directories specific
	   to C++, but do still search the other standard directories.	(This
	   option is used when building the C++ library.)

       In addition, these optimization, warning, and code generation options
       have meanings only for C++ programs:

       -fno-default-inline
	   Do not assume inline for functions defined inside a class scope.
	     Note that these functions have linkage like inline functions;
	   they just aren't inlined by default.

       -Wabi (C, Objective-C, C++ and Objective-C++ only)
	   Warn when G++ generates code that is probably not compatible with
	   the vendor-neutral C++ ABI.	Although an effort has been made to
	   warn about all such cases, there are probably some cases that are
	   not warned about, even though G++ is generating incompatible code.
	   There may also be cases where warnings are emitted even though the
	   code that is generated is compatible.

	   You should rewrite your code to avoid these warnings if you are
	   concerned about the fact that code generated by G++ may not be
	   binary compatible with code generated by other compilers.

	   The known incompatibilities in -fabi-version=2 (the default)
	   include:

	   o   A template with a non-type template parameter of reference type
	       is mangled incorrectly:

		       extern int N;
		       template <int &> struct S {};
		       void n (S<N>) {2}

	       This is fixed in -fabi-version=3.

	   o   SIMD vector types declared using "__attribute ((vector_size))"
	       are mangled in a non-standard way that does not allow for
	       overloading of functions taking vectors of different sizes.

	       The mangling is changed in -fabi-version=4.

	   The known incompatibilities in -fabi-version=1 include:

	   o   Incorrect handling of tail-padding for bit-fields.  G++ may
	       attempt to pack data into the same byte as a base class.	 For
	       example:

		       struct A { virtual void f(); int f1 : 1; };
		       struct B : public A { int f2 : 1; };

	       In this case, G++ places "B::f2" into the same byte as "A::f1";
	       other compilers do not.	You can avoid this problem by
	       explicitly padding "A" so that its size is a multiple of the
	       byte size on your platform; that causes G++ and other compilers
	       to lay out "B" identically.

	   o   Incorrect handling of tail-padding for virtual bases.  G++ does
	       not use tail padding when laying out virtual bases.  For
	       example:

		       struct A { virtual void f(); char c1; };
		       struct B { B(); char c2; };
		       struct C : public A, public virtual B {};

	       In this case, G++ does not place "B" into the tail-padding for
	       "A"; other compilers do.	 You can avoid this problem by
	       explicitly padding "A" so that its size is a multiple of its
	       alignment (ignoring virtual base classes); that causes G++ and
	       other compilers to lay out "C" identically.

	   o   Incorrect handling of bit-fields with declared widths greater
	       than that of their underlying types, when the bit-fields appear
	       in a union.  For example:

		       union U { int i : 4096; };

	       Assuming that an "int" does not have 4096 bits, G++ makes the
	       union too small by the number of bits in an "int".

	   o   Empty classes can be placed at incorrect offsets.  For example:

		       struct A {};

		       struct B {
			 A a;
			 virtual void f ();
		       };

		       struct C : public B, public A {};

	       G++ places the "A" base class of "C" at a nonzero offset; it
	       should be placed at offset zero.	 G++ mistakenly believes that
	       the "A" data member of "B" is already at offset zero.

	   o   Names of template functions whose types involve "typename" or
	       template template parameters can be mangled incorrectly.

		       template <typename Q>
		       void f(typename Q::X) {}

		       template <template <typename> class Q>
		       void f(typename Q<int>::X) {}

	       Instantiations of these templates may be mangled incorrectly.

	   It also warns about psABI-related changes.  The known psABI changes
	   at this point include:

	   o   For SysV/x86-64, unions with "long double" members are passed
	       in memory as specified in psABI.	 For example:

		       union U {
			 long double ld;
			 int i;
		       };

	       "union U" is always passed in memory.

       -Wctor-dtor-privacy (C++ and Objective-C++ only)
	   Warn when a class seems unusable because all the constructors or
	   destructors in that class are private, and it has neither friends
	   nor public static member functions.	Also warn if there are no non-
	   private methods, and there's at least one private member function
	   that isn't a constructor or destructor.

       -Wdelete-non-virtual-dtor (C++ and Objective-C++ only)
	   Warn when delete is used to destroy an instance of a class that has
	   virtual functions and non-virtual destructor. It is unsafe to
	   delete an instance of a derived class through a pointer to a base
	   class if the base class does not have a virtual destructor.	This
	   warning is enabled by -Wall.

       -Wliteral-suffix (C++ and Objective-C++ only)
	   Warn when a string or character literal is followed by a ud-suffix
	   which does not begin with an underscore.  As a conforming
	   extension, GCC treats such suffixes as separate preprocessing
	   tokens in order to maintain backwards compatibility with code that
	   uses formatting macros from "<inttypes.h>".	For example:

		   #define __STDC_FORMAT_MACROS
		   #include <inttypes.h>
		   #include <stdio.h>

		   int main() {
		     int64_t i64 = 123;
		     printf("My int64: %"PRId64"\n", i64);
		   }

	   In this case, "PRId64" is treated as a separate preprocessing
	   token.

	   This warning is enabled by default.

       -Wnarrowing (C++ and Objective-C++ only)
	   Warn when a narrowing conversion prohibited by C++11 occurs within
	   { }, e.g.

		   int i = { 2.2 }; // error: narrowing from double to int

	   This flag is included in -Wall and -Wc++11-compat.

	   With -std=c++11, -Wno-narrowing suppresses the diagnostic required
	   by the standard.  Note that this does not affect the meaning of
	   well-formed code; narrowing conversions are still considered ill-
	   formed in SFINAE context.

       -Wnoexcept (C++ and Objective-C++ only)
	   Warn when a noexcept-expression evaluates to false because of a
	   call to a function that does not have a non-throwing exception
	   specification (i.e. throw() or noexcept) but is known by the
	   compiler to never throw an exception.

       -Wnon-virtual-dtor (C++ and Objective-C++ only)
	   Warn when a class has virtual functions and an accessible non-
	   virtual destructor, in which case it is possible but unsafe to
	   delete an instance of a derived class through a pointer to the base
	   class.  This warning is also enabled if -Weffc++ is specified.

       -Wreorder (C++ and Objective-C++ only)
	   Warn when the order of member initializers given in the code does
	   not match the order in which they must be executed.	For instance:

		   struct A {
		     int i;
		     int j;
		     A(): j (0), i (1) { }
		   };

	   The compiler rearranges the member initializers for i and j to
	   match the declaration order of the members, emitting a warning to
	   that effect.	 This warning is enabled by -Wall.

       -fext-numeric-literals (C++ and Objective-C++ only)
	   Accept imaginary, fixed-point, or machine-defined literal number
	   suffixes as GNU extensions.	When this option is turned off these
	   suffixes are treated as C++11 user-defined literal numeric
	   suffixes.  This is on by default for all pre-C++11 dialects and all
	   GNU dialects: -std=c++98, -std=gnu++98, -std=gnu++11, -std=gnu++1y.
	   This option is off by default for ISO C++11 onwards (-std=c++11,
	   ...).

       The following -W... options are not affected by -Wall.

       -Weffc++ (C++ and Objective-C++ only)
	   Warn about violations of the following style guidelines from Scott
	   Meyers' Effective C++, Second Edition book:

	   o   Item 11:	 Define a copy constructor and an assignment operator
	       for classes with dynamically-allocated memory.

	   o   Item 12:	 Prefer initialization to assignment in constructors.

	   o   Item 14:	 Make destructors virtual in base classes.

	   o   Item 15:	 Have "operator=" return a reference to *this.

	   o   Item 23:	 Don't try to return a reference when you must return
	       an object.

	   Also warn about violations of the following style guidelines from
	   Scott Meyers' More Effective C++ book:

	   o   Item 6:	Distinguish between prefix and postfix forms of
	       increment and decrement operators.

	   o   Item 7:	Never overload "&&", "||", or ",".

	   When selecting this option, be aware that the standard library
	   headers do not obey all of these guidelines; use grep -v to filter
	   out those warnings.

       -Wstrict-null-sentinel (C++ and Objective-C++ only)
	   Warn about the use of an uncasted "NULL" as sentinel.  When
	   compiling only with GCC this is a valid sentinel, as "NULL" is
	   defined to "__null".	 Although it is a null pointer constant rather
	   than a null pointer, it is guaranteed to be of the same size as a
	   pointer.  But this use is not portable across different compilers.

       -Wno-non-template-friend (C++ and Objective-C++ only)
	   Disable warnings when non-templatized friend functions are declared
	   within a template.  Since the advent of explicit template
	   specification support in G++, if the name of the friend is an
	   unqualified-id (i.e., friend foo(int)), the C++ language
	   specification demands that the friend declare or define an
	   ordinary, nontemplate function.  (Section 14.5.3).  Before G++
	   implemented explicit specification, unqualified-ids could be
	   interpreted as a particular specialization of a templatized
	   function.  Because this non-conforming behavior is no longer the
	   default behavior for G++, -Wnon-template-friend allows the compiler
	   to check existing code for potential trouble spots and is on by
	   default.  This new compiler behavior can be turned off with
	   -Wno-non-template-friend, which keeps the conformant compiler code
	   but disables the helpful warning.

       -Wold-style-cast (C++ and Objective-C++ only)
	   Warn if an old-style (C-style) cast to a non-void type is used
	   within a C++ program.  The new-style casts (dynamic_cast,
	   static_cast, reinterpret_cast, and const_cast) are less vulnerable
	   to unintended effects and much easier to search for.

       -Woverloaded-virtual (C++ and Objective-C++ only)
	   Warn when a function declaration hides virtual functions from a
	   base class.	For example, in:

		   struct A {
		     virtual void f();
		   };

		   struct B: public A {
		     void f(int);
		   };

	   the "A" class version of "f" is hidden in "B", and code like:

		   B* b;
		   b->f();

	   fails to compile.

       -Wno-pmf-conversions (C++ and Objective-C++ only)
	   Disable the diagnostic for converting a bound pointer to member
	   function to a plain pointer.

       -Wsign-promo (C++ and Objective-C++ only)
	   Warn when overload resolution chooses a promotion from unsigned or
	   enumerated type to a signed type, over a conversion to an unsigned
	   type of the same size.  Previous versions of G++ tried to preserve
	   unsignedness, but the standard mandates the current behavior.

   Options Controlling Objective-C and Objective-C++ Dialects
       (NOTE: This manual does not describe the Objective-C and Objective-C++
       languages themselves.

       This section describes the command-line options that are only
       meaningful for Objective-C and Objective-C++ programs.  You can also
       use most of the language-independent GNU compiler options.  For
       example, you might compile a file "some_class.m" like this:

	       gcc -g -fgnu-runtime -O -c some_class.m

       In this example, -fgnu-runtime is an option meant only for Objective-C
       and Objective-C++ programs; you can use the other options with any
       language supported by GCC.

       Note that since Objective-C is an extension of the C language,
       Objective-C compilations may also use options specific to the C front-
       end (e.g., -Wtraditional).  Similarly, Objective-C++ compilations may
       use C++-specific options (e.g., -Wabi).

       Here is a list of options that are only for compiling Objective-C and
       Objective-C++ programs:

       -fconstant-string-class=class-name
	   Use class-name as the name of the class to instantiate for each
	   literal string specified with the syntax "@"..."".  The default
	   class name is "NXConstantString" if the GNU runtime is being used,
	   and "NSConstantString" if the NeXT runtime is being used (see
	   below).  The -fconstant-cfstrings option, if also present,
	   overrides the -fconstant-string-class setting and cause "@"...""
	   literals to be laid out as constant CoreFoundation strings.

       -fgnu-runtime
	   Generate object code compatible with the standard GNU Objective-C
	   runtime.  This is the default for most types of systems.

       -fnext-runtime
	   Generate output compatible with the NeXT runtime.  This is the
	   default for NeXT-based systems, including Darwin and Mac OS X.  The
	   macro "__NEXT_RUNTIME__" is predefined if (and only if) this option
	   is used.

       -fno-nil-receivers
	   Assume that all Objective-C message dispatches ("[receiver
	   message:arg]") in this translation unit ensure that the receiver is
	   not "nil".  This allows for more efficient entry points in the
	   runtime to be used.	This option is only available in conjunction
	   with the NeXT runtime and ABI version 0 or 1.

       -fobjc-abi-version=n
	   Use version n of the Objective-C ABI for the selected runtime.
	   This option is currently supported only for the NeXT runtime.  In
	   that case, Version 0 is the traditional (32-bit) ABI without
	   support for properties and other Objective-C 2.0 additions.
	   Version 1 is the traditional (32-bit) ABI with support for
	   properties and other Objective-C 2.0 additions.  Version 2 is the
	   modern (64-bit) ABI.	 If nothing is specified, the default is
	   Version 0 on 32-bit target machines, and Version 2 on 64-bit target
	   machines.

       -fobjc-call-cxx-cdtors
	   For each Objective-C class, check if any of its instance variables
	   is a C++ object with a non-trivial default constructor.  If so,
	   synthesize a special "- (id) .cxx_construct" instance method which
	   runs non-trivial default constructors on any such instance
	   variables, in order, and then return "self".	 Similarly, check if
	   any instance variable is a C++ object with a non-trivial
	   destructor, and if so, synthesize a special "- (void)
	   .cxx_destruct" method which runs all such default destructors, in
	   reverse order.

	   The "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods
	   thusly generated only operate on instance variables declared in the
	   current Objective-C class, and not those inherited from
	   superclasses.  It is the responsibility of the Objective-C runtime
	   to invoke all such methods in an object's inheritance hierarchy.
	   The "- (id) .cxx_construct" methods are invoked by the runtime
	   immediately after a new object instance is allocated; the "- (void)
	   .cxx_destruct" methods are invoked immediately before the runtime
	   deallocates an object instance.

	   As of this writing, only the NeXT runtime on Mac OS X 10.4 and
	   later has support for invoking the "- (id) .cxx_construct" and "-
	   (void) .cxx_destruct" methods.

       -fobjc-direct-dispatch
	   Allow fast jumps to the message dispatcher.	On Darwin this is
	   accomplished via the comm page.

       -fobjc-exceptions
	   Enable syntactic support for structured exception handling in
	   Objective-C, similar to what is offered by C++ and Java.  This
	   option is required to use the Objective-C keywords @try, @throw,
	   @catch, @finally and @synchronized.	This option is available with
	   both the GNU runtime and the NeXT runtime (but not available in
	   conjunction with the NeXT runtime on Mac OS X 10.2 and earlier).

       -fobjc-gc
	   Enable garbage collection (GC) in Objective-C and Objective-C++
	   programs.  This option is only available with the NeXT runtime; the
	   GNU runtime has a different garbage collection implementation that
	   does not require special compiler flags.

       -fobjc-nilcheck
	   For the NeXT runtime with version 2 of the ABI, check for a nil
	   receiver in method invocations before doing the actual method call.
	   This is the default and can be disabled using -fno-objc-nilcheck.
	   Class methods and super calls are never checked for nil in this way
	   no matter what this flag is set to.	Currently this flag does
	   nothing when the GNU runtime, or an older version of the NeXT
	   runtime ABI, is used.

       -fobjc-std=objc1
	   Conform to the language syntax of Objective-C 1.0, the language
	   recognized by GCC 4.0.  This only affects the Objective-C additions
	   to the C/C++ language; it does not affect conformance to C/C++
	   standards, which is controlled by the separate C/C++ dialect option
	   flags.  When this option is used with the Objective-C or
	   Objective-C++ compiler, any Objective-C syntax that is not
	   recognized by GCC 4.0 is rejected.  This is useful if you need to
	   make sure that your Objective-C code can be compiled with older
	   versions of GCC.

       -freplace-objc-classes
	   Emit a special marker instructing ld(1) not to statically link in
	   the resulting object file, and allow dyld(1) to load it in at run
	   time instead.  This is used in conjunction with the Fix-and-
	   Continue debugging mode, where the object file in question may be
	   recompiled and dynamically reloaded in the course of program
	   execution, without the need to restart the program itself.
	   Currently, Fix-and-Continue functionality is only available in
	   conjunction with the NeXT runtime on Mac OS X 10.3 and later.

       -fzero-link
	   When compiling for the NeXT runtime, the compiler ordinarily
	   replaces calls to "objc_getClass("...")" (when the name of the
	   class is known at compile time) with static class references that
	   get initialized at load time, which improves run-time performance.
	   Specifying the -fzero-link flag suppresses this behavior and causes
	   calls to "objc_getClass("...")"  to be retained.  This is useful in
	   Zero-Link debugging mode, since it allows for individual class
	   implementations to be modified during program execution.  The GNU
	   runtime currently always retains calls to "objc_get_class("...")"
	   regardless of command-line options.

       -gen-decls
	   Dump interface declarations for all classes seen in the source file
	   to a file named sourcename.decl.

       -Wassign-intercept (Objective-C and Objective-C++ only)
	   Warn whenever an Objective-C assignment is being intercepted by the
	   garbage collector.

       -Wno-protocol (Objective-C and Objective-C++ only)
	   If a class is declared to implement a protocol, a warning is issued
	   for every method in the protocol that is not implemented by the
	   class.  The default behavior is to issue a warning for every method
	   not explicitly implemented in the class, even if a method
	   implementation is inherited from the superclass.  If you use the
	   -Wno-protocol option, then methods inherited from the superclass
	   are considered to be implemented, and no warning is issued for
	   them.

       -Wselector (Objective-C and Objective-C++ only)
	   Warn if multiple methods of different types for the same selector
	   are found during compilation.  The check is performed on the list
	   of methods in the final stage of compilation.  Additionally, a
	   check is performed for each selector appearing in a
	   "@selector(...)"  expression, and a corresponding method for that
	   selector has been found during compilation.	Because these checks
	   scan the method table only at the end of compilation, these
	   warnings are not produced if the final stage of compilation is not
	   reached, for example because an error is found during compilation,
	   or because the -fsyntax-only option is being used.

       -Wstrict-selector-match (Objective-C and Objective-C++ only)
	   Warn if multiple methods with differing argument and/or return
	   types are found for a given selector when attempting to send a
	   message using this selector to a receiver of type "id" or "Class".
	   When this flag is off (which is the default behavior), the compiler
	   omits such warnings if any differences found are confined to types
	   that share the same size and alignment.

       -Wundeclared-selector (Objective-C and Objective-C++ only)
	   Warn if a "@selector(...)" expression referring to an undeclared
	   selector is found.  A selector is considered undeclared if no
	   method with that name has been declared before the "@selector(...)"
	   expression, either explicitly in an @interface or @protocol
	   declaration, or implicitly in an @implementation section.  This
	   option always performs its checks as soon as a "@selector(...)"
	   expression is found, while -Wselector only performs its checks in
	   the final stage of compilation.  This also enforces the coding
	   style convention that methods and selectors must be declared before
	   being used.

       -print-objc-runtime-info
	   Generate C header describing the largest structure that is passed
	   by value, if any.

   Options to Control Diagnostic Messages Formatting
       Traditionally, diagnostic messages have been formatted irrespective of
       the output device's aspect (e.g. its width, ...).  You can use the
       options described below to control the formatting algorithm for
       diagnostic messages, e.g. how many characters per line, how often
       source location information should be reported.	Note that some
       language front ends may not honor these options.

       -fmessage-length=n
	   Try to format error messages so that they fit on lines of about n
	   characters.	The default is 72 characters for g++ and 0 for the
	   rest of the front ends supported by GCC.  If n is zero, then no
	   line-wrapping is done; each error message appears on a single line.

       -fdiagnostics-show-location=once
	   Only meaningful in line-wrapping mode.  Instructs the diagnostic
	   messages reporter to emit source location information once; that
	   is, in case the message is too long to fit on a single physical
	   line and has to be wrapped, the source location won't be emitted
	   (as prefix) again, over and over, in subsequent continuation lines.
	   This is the default behavior.

       -fdiagnostics-show-location=every-line
	   Only meaningful in line-wrapping mode.  Instructs the diagnostic
	   messages reporter to emit the same source location information (as
	   prefix) for physical lines that result from the process of breaking
	   a message which is too long to fit on a single line.

       -fdiagnostics-color[=WHEN]
       -fno-diagnostics-color
	   Use color in diagnostics.  WHEN is never, always, or auto.  The
	   default is auto.  auto means to use color only when the standard
	   error is a terminal.	 The forms -fdiagnostics-color and
	   -fno-diagnostics-color are aliases for -fdiagnostics-color=always
	   and -fdiagnostics-color=never, respectively.

	   The colors are defined by the environment variable GCC_COLORS.  Its
	   value is a colon-separated list of capabilities and Select Graphic
	   Rendition (SGR) substrings. SGR commands are interpreted by the
	   terminal or terminal emulator.  (See the section in the
	   documentation of your text terminal for permitted values and their
	   meanings as character attributes.)  These substring values are
	   integers in decimal representation and can be concatenated with
	   semicolons.	Common values to concatenate include 1 for bold, 4 for
	   underline, 5 for blink, 7 for inverse, 39 for default foreground
	   color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode
	   foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color
	   modes foreground colors, 49 for default background color, 40 to 47
	   for background colors, 100 to 107 for 16-color mode background
	   colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes
	   background colors.

	   The default GCC_COLORS is
	   error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01
	   where 01;31 is bold red, 01;35 is bold magenta, 01;36 is bold cyan,
	   01;32 is bold green and 01 is bold. Setting GCC_COLORS to the empty
	   string disables colors.  Supported capabilities are as follows.

	   "error="
	       SGR substring for error: markers.

	   "warning="
	       SGR substring for warning: markers.

	   "note="
	       SGR substring for note: markers.

	   "caret="
	       SGR substring for caret line.

	   "locus="
	       SGR substring for location information, file:line or
	       file:line:column etc.

	   "quote="
	       SGR substring for information printed within quotes.

       -fno-diagnostics-show-option
	   By default, each diagnostic emitted includes text indicating the
	   command-line option that directly controls the diagnostic (if such
	   an option is known to the diagnostic machinery).  Specifying the
	   -fno-diagnostics-show-option flag suppresses that behavior.

       -fno-diagnostics-show-caret
	   By default, each diagnostic emitted includes the original source
	   line and a caret '^' indicating the column.	This option suppresses
	   this information.

   Options to Request or Suppress Warnings
       Warnings are diagnostic messages that report constructions that are not
       inherently erroneous but that are risky or suggest there may have been
       an error.

       The following language-independent options do not enable specific
       warnings but control the kinds of diagnostics produced by GCC.

       -fsyntax-only
	   Check the code for syntax errors, but don't do anything beyond
	   that.

       -fmax-errors=n
	   Limits the maximum number of error messages to n, at which point
	   GCC bails out rather than attempting to continue processing the
	   source code.	 If n is 0 (the default), there is no limit on the
	   number of error messages produced.  If -Wfatal-errors is also
	   specified, then -Wfatal-errors takes precedence over this option.

       -w  Inhibit all warning messages.

       -Werror
	   Make all warnings into errors.

       -Werror=
	   Make the specified warning into an error.  The specifier for a
	   warning is appended; for example -Werror=switch turns the warnings
	   controlled by -Wswitch into errors.	This switch takes a negative
	   form, to be used to negate -Werror for specific warnings; for
	   example -Wno-error=switch makes -Wswitch warnings not be errors,
	   even when -Werror is in effect.

	   The warning message for each controllable warning includes the
	   option that controls the warning.  That option can then be used
	   with -Werror= and -Wno-error= as described above.  (Printing of the
	   option in the warning message can be disabled using the
	   -fno-diagnostics-show-option flag.)

	   Note that specifying -Werror=foo automatically implies -Wfoo.
	   However, -Wno-error=foo does not imply anything.

       -Wfatal-errors
	   This option causes the compiler to abort compilation on the first
	   error occurred rather than trying to keep going and printing
	   further error messages.

       You can request many specific warnings with options beginning with -W,
       for example -Wimplicit to request warnings on implicit declarations.
       Each of these specific warning options also has a negative form
       beginning -Wno- to turn off warnings; for example, -Wno-implicit.  This
       manual lists only one of the two forms, whichever is not the default.
       For further language-specific options also refer to C++ Dialect Options
       and Objective-C and Objective-C++ Dialect Options.

       When an unrecognized warning option is requested (e.g.,
       -Wunknown-warning), GCC emits a diagnostic stating that the option is
       not recognized.	However, if the -Wno- form is used, the behavior is
       slightly different: no diagnostic is produced for -Wno-unknown-warning
       unless other diagnostics are being produced.  This allows the use of
       new -Wno- options with old compilers, but if something goes wrong, the
       compiler warns that an unrecognized option is present.

       -Wpedantic
       -pedantic
	   Issue all the warnings demanded by strict ISO C and ISO C++; reject
	   all programs that use forbidden extensions, and some other programs
	   that do not follow ISO C and ISO C++.  For ISO C, follows the
	   version of the ISO C standard specified by any -std option used.

	   Valid ISO C and ISO C++ programs should compile properly with or
	   without this option (though a rare few require -ansi or a -std
	   option specifying the required version of ISO C).  However, without
	   this option, certain GNU extensions and traditional C and C++
	   features are supported as well.  With this option, they are
	   rejected.

	   -Wpedantic does not cause warning messages for use of the alternate
	   keywords whose names begin and end with __.	Pedantic warnings are
	   also disabled in the expression that follows "__extension__".
	   However, only system header files should use these escape routes;
	   application programs should avoid them.

	   Some users try to use -Wpedantic to check programs for strict ISO C
	   conformance.	 They soon find that it does not do quite what they
	   want: it finds some non-ISO practices, but not all---only those for
	   which ISO C requires a diagnostic, and some others for which
	   diagnostics have been added.

	   A feature to report any failure to conform to ISO C might be useful
	   in some instances, but would require considerable additional work
	   and would be quite different from -Wpedantic.  We don't have plans
	   to support such a feature in the near future.

	   Where the standard specified with -std represents a GNU extended
	   dialect of C, such as gnu90 or gnu99, there is a corresponding base
	   standard, the version of ISO C on which the GNU extended dialect is
	   based.  Warnings from -Wpedantic are given where they are required
	   by the base standard.  (It does not make sense for such warnings to
	   be given only for features not in the specified GNU C dialect,
	   since by definition the GNU dialects of C include all features the
	   compiler supports with the given option, and there would be nothing
	   to warn about.)

       -pedantic-errors
	   Like -Wpedantic, except that errors are produced rather than
	   warnings.

       -Wall
	   This enables all the warnings about constructions that some users
	   consider questionable, and that are easy to avoid (or modify to
	   prevent the warning), even in conjunction with macros.  This also
	   enables some language-specific warnings described in C++ Dialect
	   Options and Objective-C and Objective-C++ Dialect Options.

	   -Wall turns on the following warning flags:

	   -Waddress -Warray-bounds (only with -O2) -Wc++11-compat
	   -Wchar-subscripts -Wenum-compare (in C/ObjC; this is on by default
	   in C++) -Wimplicit-int (C and Objective-C only)
	   -Wimplicit-function-declaration (C and Objective-C only) -Wcomment
	   -Wformat -Wmain (only for C/ObjC and unless -ffreestanding)
	   -Wmaybe-uninitialized -Wmissing-braces (only for C/ObjC) -Wnonnull
	   -Wparentheses -Wpointer-sign -Wreorder -Wreturn-type
	   -Wsequence-point -Wsign-compare (only in C++) -Wstrict-aliasing
	   -Wstrict-overflow=1 -Wswitch -Wtrigraphs -Wuninitialized
	   -Wunknown-pragmas -Wunused-function -Wunused-label -Wunused-value
	   -Wunused-variable -Wvolatile-register-var

	   Note that some warning flags are not implied by -Wall.  Some of
	   them warn about constructions that users generally do not consider
	   questionable, but which occasionally you might wish to check for;
	   others warn about constructions that are necessary or hard to avoid
	   in some cases, and there is no simple way to modify the code to
	   suppress the warning. Some of them are enabled by -Wextra but many
	   of them must be enabled individually.

       -Wextra
	   This enables some extra warning flags that are not enabled by
	   -Wall. (This option used to be called -W.  The older name is still
	   supported, but the newer name is more descriptive.)

	   -Wclobbered -Wempty-body -Wignored-qualifiers
	   -Wmissing-field-initializers -Wmissing-parameter-type (C only)
	   -Wold-style-declaration (C only) -Woverride-init -Wsign-compare
	   -Wtype-limits -Wuninitialized -Wunused-parameter (only with
	   -Wunused or -Wall) -Wunused-but-set-parameter (only with -Wunused
	   or -Wall)

	   The option -Wextra also prints warning messages for the following
	   cases:

	   o   A pointer is compared against integer zero with <, <=, >, or
	       >=.

	   o   (C++ only) An enumerator and a non-enumerator both appear in a
	       conditional expression.

	   o   (C++ only) Ambiguous virtual bases.

	   o   (C++ only) Subscripting an array that has been declared
	       register.

	   o   (C++ only) Taking the address of a variable that has been
	       declared register.

	   o   (C++ only) A base class is not initialized in a derived class's
	       copy constructor.

       -Wchar-subscripts
	   Warn if an array subscript has type "char".	This is a common cause
	   of error, as programmers often forget that this type is signed on
	   some machines.  This warning is enabled by -Wall.

       -Wcomment
	   Warn whenever a comment-start sequence /* appears in a /* comment,
	   or whenever a Backslash-Newline appears in a // comment.  This
	   warning is enabled by -Wall.

       -Wno-coverage-mismatch
	   Warn if feedback profiles do not match when using the -fprofile-use
	   option.  If a source file is changed between compiling with
	   -fprofile-gen and with -fprofile-use, the files with the profile
	   feedback can fail to match the source file and GCC cannot use the
	   profile feedback information.  By default, this warning is enabled
	   and is treated as an error.	-Wno-coverage-mismatch can be used to
	   disable the warning or -Wno-error=coverage-mismatch can be used to
	   disable the error.  Disabling the error for this warning can result
	   in poorly optimized code and is useful only in the case of very
	   minor changes such as bug fixes to an existing code-base.
	   Completely disabling the warning is not recommended.

       -Wno-cpp
	   (C, Objective-C, C++, Objective-C++ and Fortran only)

	   Suppress warning messages emitted by "#warning" directives.

       -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only)
	   Give a warning when a value of type "float" is implicitly promoted
	   to "double".	 CPUs with a 32-bit "single-precision" floating-point
	   unit implement "float" in hardware, but emulate "double" in
	   software.  On such a machine, doing computations using "double"
	   values is much more expensive because of the overhead required for
	   software emulation.

	   It is easy to accidentally do computations with "double" because
	   floating-point literals are implicitly of type "double".  For
	   example, in:

		   float area(float radius)
		   {
		      return 3.14159 * radius * radius;
		   }

	   the compiler performs the entire computation with "double" because
	   the floating-point literal is a "double".

       -Wformat
       -Wformat=n
	   Check calls to "printf" and "scanf", etc., to make sure that the
	   arguments supplied have types appropriate to the format string
	   specified, and that the conversions specified in the format string
	   make sense.	This includes standard functions, and others specified
	   by format attributes, in the "printf", "scanf", "strftime" and
	   "strfmon" (an X/Open extension, not in the C standard) families (or
	   other target-specific families).  Which functions are checked
	   without format attributes having been specified depends on the
	   standard version selected, and such checks of functions without the
	   attribute specified are disabled by -ffreestanding or -fno-builtin.

	   The formats are checked against the format features supported by
	   GNU libc version 2.2.  These include all ISO C90 and C99 features,
	   as well as features from the Single Unix Specification and some BSD
	   and GNU extensions.	Other library implementations may not support
	   all these features; GCC does not support warning about features
	   that go beyond a particular library's limitations.  However, if
	   -Wpedantic is used with -Wformat, warnings are given about format
	   features not in the selected standard version (but not for
	   "strfmon" formats, since those are not in any version of the C
	   standard).

	   -Wformat=1
	   -Wformat
	       Option -Wformat is equivalent to -Wformat=1, and -Wno-format is
	       equivalent to -Wformat=0.  Since -Wformat also checks for null
	       format arguments for several functions, -Wformat also implies
	       -Wnonnull.  Some aspects of this level of format checking can
	       be disabled by the options: -Wno-format-contains-nul,
	       -Wno-format-extra-args, and -Wno-format-zero-length.  -Wformat
	       is enabled by -Wall.

	   -Wno-format-contains-nul
	       If -Wformat is specified, do not warn about format strings that
	       contain NUL bytes.

	   -Wno-format-extra-args
	       If -Wformat is specified, do not warn about excess arguments to
	       a "printf" or "scanf" format function.  The C standard
	       specifies that such arguments are ignored.

	       Where the unused arguments lie between used arguments that are
	       specified with $ operand number specifications, normally
	       warnings are still given, since the implementation could not
	       know what type to pass to "va_arg" to skip the unused
	       arguments.  However, in the case of "scanf" formats, this
	       option suppresses the warning if the unused arguments are all
	       pointers, since the Single Unix Specification says that such
	       unused arguments are allowed.

	   -Wno-format-zero-length
	       If -Wformat is specified, do not warn about zero-length
	       formats.	 The C standard specifies that zero-length formats are
	       allowed.

	   -Wformat=2
	       Enable -Wformat plus additional format checks.  Currently
	       equivalent to -Wformat -Wformat-nonliteral -Wformat-security
	       -Wformat-y2k.

	   -Wformat-nonliteral
	       If -Wformat is specified, also warn if the format string is not
	       a string literal and so cannot be checked, unless the format
	       function takes its format arguments as a "va_list".

	   -Wformat-security
	       If -Wformat is specified, also warn about uses of format
	       functions that represent possible security problems.  At
	       present, this warns about calls to "printf" and "scanf"
	       functions where the format string is not a string literal and
	       there are no format arguments, as in "printf (foo);".  This may
	       be a security hole if the format string came from untrusted
	       input and contains %n.  (This is currently a subset of what
	       -Wformat-nonliteral warns about, but in future warnings may be
	       added to -Wformat-security that are not included in
	       -Wformat-nonliteral.)

	   -Wformat-y2k
	       If -Wformat is specified, also warn about "strftime" formats
	       that may yield only a two-digit year.

       -Wnonnull
	   Warn about passing a null pointer for arguments marked as requiring
	   a non-null value by the "nonnull" function attribute.

	   -Wnonnull is included in -Wall and -Wformat.	 It can be disabled
	   with the -Wno-nonnull option.

       -Winit-self (C, C++, Objective-C and Objective-C++ only)
	   Warn about uninitialized variables that are initialized with
	   themselves.	Note this option can only be used with the
	   -Wuninitialized option.

	   For example, GCC warns about "i" being uninitialized in the
	   following snippet only when -Winit-self has been specified:

		   int f()
		   {
		     int i = i;
		     return i;
		   }

	   This warning is enabled by -Wall in C++.

       -Wimplicit-int (C and Objective-C only)
	   Warn when a declaration does not specify a type.  This warning is
	   enabled by -Wall.

       -Wimplicit-function-declaration (C and Objective-C only)
	   Give a warning whenever a function is used before being declared.
	   In C99 mode (-std=c99 or -std=gnu99), this warning is enabled by
	   default and it is made into an error by -pedantic-errors. This
	   warning is also enabled by -Wall.

       -Wimplicit (C and Objective-C only)
	   Same as -Wimplicit-int and -Wimplicit-function-declaration.	This
	   warning is enabled by -Wall.

       -Wignored-qualifiers (C and C++ only)
	   Warn if the return type of a function has a type qualifier such as
	   "const".  For ISO C such a type qualifier has no effect, since the
	   value returned by a function is not an lvalue.  For C++, the
	   warning is only emitted for scalar types or "void".	ISO C
	   prohibits qualified "void" return types on function definitions, so
	   such return types always receive a warning even without this
	   option.

	   This warning is also enabled by -Wextra.

       -Wmain
	   Warn if the type of main is suspicious.  main should be a function
	   with external linkage, returning int, taking either zero arguments,
	   two, or three arguments of appropriate types.  This warning is
	   enabled by default in C++ and is enabled by either -Wall or
	   -Wpedantic.

       -Wmissing-braces
	   Warn if an aggregate or union initializer is not fully bracketed.
	   In the following example, the initializer for a is not fully
	   bracketed, but that for b is fully bracketed.  This warning is
	   enabled by -Wall in C.

		   int a[2][2] = { 0, 1, 2, 3 };
		   int b[2][2] = { { 0, 1 }, { 2, 3 } };

	   This warning is enabled by -Wall.

       -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
	   Warn if a user-supplied include directory does not exist.

       -Wparentheses
	   Warn if parentheses are omitted in certain contexts, such as when
	   there is an assignment in a context where a truth value is
	   expected, or when operators are nested whose precedence people
	   often get confused about.

	   Also warn if a comparison like x<=y<=z appears; this is equivalent
	   to (x<=y ? 1 : 0) <= z, which is a different interpretation from
	   that of ordinary mathematical notation.

	   Also warn about constructions where there may be confusion to which
	   "if" statement an "else" branch belongs.  Here is an example of
	   such a case:

		   {
		     if (a)
		       if (b)
			 foo ();
		     else
		       bar ();
		   }

	   In C/C++, every "else" branch belongs to the innermost possible
	   "if" statement, which in this example is "if (b)".  This is often
	   not what the programmer expected, as illustrated in the above
	   example by indentation the programmer chose.	 When there is the
	   potential for this confusion, GCC issues a warning when this flag
	   is specified.  To eliminate the warning, add explicit braces around
	   the innermost "if" statement so there is no way the "else" can
	   belong to the enclosing "if".  The resulting code looks like this:

		   {
		     if (a)
		       {
			 if (b)
			   foo ();
			 else
			   bar ();
		       }
		   }

	   Also warn for dangerous uses of the GNU extension to "?:" with
	   omitted middle operand. When the condition in the "?": operator is
	   a boolean expression, the omitted value is always 1.	 Often
	   programmers expect it to be a value computed inside the conditional
	   expression instead.

	   This warning is enabled by -Wall.

       -Wsequence-point
	   Warn about code that may have undefined semantics because of
	   violations of sequence point rules in the C and C++ standards.

	   The C and C++ standards define the order in which expressions in a
	   C/C++ program are evaluated in terms of sequence points, which
	   represent a partial ordering between the execution of parts of the
	   program: those executed before the sequence point, and those
	   executed after it.  These occur after the evaluation of a full
	   expression (one which is not part of a larger expression), after
	   the evaluation of the first operand of a "&&", "||", "? :" or ","
	   (comma) operator, before a function is called (but after the
	   evaluation of its arguments and the expression denoting the called
	   function), and in certain other places.  Other than as expressed by
	   the sequence point rules, the order of evaluation of subexpressions
	   of an expression is not specified.  All these rules describe only a
	   partial order rather than a total order, since, for example, if two
	   functions are called within one expression with no sequence point
	   between them, the order in which the functions are called is not
	   specified.  However, the standards committee have ruled that
	   function calls do not overlap.

	   It is not specified when between sequence points modifications to
	   the values of objects take effect.  Programs whose behavior depends
	   on this have undefined behavior; the C and C++ standards specify
	   that "Between the previous and next sequence point an object shall
	   have its stored value modified at most once by the evaluation of an
	   expression.	Furthermore, the prior value shall be read only to
	   determine the value to be stored.".	If a program breaks these
	   rules, the results on any particular implementation are entirely
	   unpredictable.

	   Examples of code with undefined behavior are "a = a++;", "a[n] =
	   b[n++]" and "a[i++] = i;".  Some more complicated cases are not
	   diagnosed by this option, and it may give an occasional false
	   positive result, but in general it has been found fairly effective
	   at detecting this sort of problem in programs.

	   The standard is worded confusingly, therefore there is some debate
	   over the precise meaning of the sequence point rules in subtle
	   cases.  Links to discussions of the problem, including proposed
	   formal definitions, may be found on the GCC readings page, at
	   <http://gcc.gnu.org/readings.html>.

	   This warning is enabled by -Wall for C and C++.

       -Wno-return-local-addr
	   Do not warn about returning a pointer (or in C++, a reference) to a
	   variable that goes out of scope after the function returns.

       -Wreturn-type
	   Warn whenever a function is defined with a return type that
	   defaults to "int".  Also warn about any "return" statement with no
	   return value in a function whose return type is not "void" (falling
	   off the end of the function body is considered returning without a
	   value), and about a "return" statement with an expression in a
	   function whose return type is "void".

	   For C++, a function without return type always produces a
	   diagnostic message, even when -Wno-return-type is specified.	 The
	   only exceptions are main and functions defined in system headers.

	   This warning is enabled by -Wall.

       -Wswitch
	   Warn whenever a "switch" statement has an index of enumerated type
	   and lacks a "case" for one or more of the named codes of that
	   enumeration.	 (The presence of a "default" label prevents this
	   warning.)  "case" labels outside the enumeration range also provoke
	   warnings when this option is used (even if there is a "default"
	   label).  This warning is enabled by -Wall.

       -Wswitch-default
	   Warn whenever a "switch" statement does not have a "default" case.

       -Wswitch-enum
	   Warn whenever a "switch" statement has an index of enumerated type
	   and lacks a "case" for one or more of the named codes of that
	   enumeration.	 "case" labels outside the enumeration range also
	   provoke warnings when this option is used.  The only difference
	   between -Wswitch and this option is that this option gives a
	   warning about an omitted enumeration code even if there is a
	   "default" label.

       -Wsync-nand (C and C++ only)
	   Warn when "__sync_fetch_and_nand" and "__sync_nand_and_fetch"
	   built-in functions are used.	 These functions changed semantics in
	   GCC 4.4.

       -Wtrigraphs
	   Warn if any trigraphs are encountered that might change the meaning
	   of the program (trigraphs within comments are not warned about).
	   This warning is enabled by -Wall.

       -Wunused-but-set-parameter
	   Warn whenever a function parameter is assigned to, but otherwise
	   unused (aside from its declaration).

	   To suppress this warning use the unused attribute.

	   This warning is also enabled by -Wunused together with -Wextra.

       -Wunused-but-set-variable
	   Warn whenever a local variable is assigned to, but otherwise unused
	   (aside from its declaration).  This warning is enabled by -Wall.

	   To suppress this warning use the unused attribute.

	   This warning is also enabled by -Wunused, which is enabled by
	   -Wall.

       -Wunused-function
	   Warn whenever a static function is declared but not defined or a
	   non-inline static function is unused.  This warning is enabled by
	   -Wall.

       -Wunused-label
	   Warn whenever a label is declared but not used.  This warning is
	   enabled by -Wall.

	   To suppress this warning use the unused attribute.

       -Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only)
	   Warn when a typedef locally defined in a function is not used.
	   This warning is enabled by -Wall.

       -Wunused-parameter
	   Warn whenever a function parameter is unused aside from its
	   declaration.

	   To suppress this warning use the unused attribute.

       -Wno-unused-result
	   Do not warn if a caller of a function marked with attribute
	   "warn_unused_result" does not use its return value. The default is
	   -Wunused-result.

       -Wunused-variable
	   Warn whenever a local variable or non-constant static variable is
	   unused aside from its declaration.  This warning is enabled by
	   -Wall.

	   To suppress this warning use the unused attribute.

       -Wunused-value
	   Warn whenever a statement computes a result that is explicitly not
	   used. To suppress this warning cast the unused expression to void.
	   This includes an expression-statement or the left-hand side of a
	   comma expression that contains no side effects. For example, an
	   expression such as x[i,j] causes a warning, while x[(void)i,j] does
	   not.

	   This warning is enabled by -Wall.

       -Wunused
	   All the above -Wunused options combined.

	   In order to get a warning about an unused function parameter, you
	   must either specify -Wextra -Wunused (note that -Wall implies
	   -Wunused), or separately specify -Wunused-parameter.

       -Wuninitialized
	   Warn if an automatic variable is used without first being
	   initialized or if a variable may be clobbered by a "setjmp" call.
	   In C++, warn if a non-static reference or non-static const member
	   appears in a class without constructors.

	   If you want to warn about code that uses the uninitialized value of
	   the variable in its own initializer, use the -Winit-self option.

	   These warnings occur for individual uninitialized or clobbered
	   elements of structure, union or array variables as well as for
	   variables that are uninitialized or clobbered as a whole.  They do
	   not occur for variables or elements declared "volatile".  Because
	   these warnings depend on optimization, the exact variables or
	   elements for which there are warnings depends on the precise
	   optimization options and version of GCC used.

	   Note that there may be no warning about a variable that is used
	   only to compute a value that itself is never used, because such
	   computations may be deleted by data flow analysis before the
	   warnings are printed.

       -Wmaybe-uninitialized
	   For an automatic variable, if there exists a path from the function
	   entry to a use of the variable that is initialized, but there exist
	   some other paths for which the variable is not initialized, the
	   compiler emits a warning if it cannot prove the uninitialized paths
	   are not executed at run time. These warnings are made optional
	   because GCC is not smart enough to see all the reasons why the code
	   might be correct in spite of appearing to have an error.  Here is
	   one example of how this can happen:

		   {
		     int x;
		     switch (y)
		       {
		       case 1: x = 1;
			 break;
		       case 2: x = 4;
			 break;
		       case 3: x = 5;
		       }
		     foo (x);
		   }

	   If the value of "y" is always 1, 2 or 3, then "x" is always
	   initialized, but GCC doesn't know this. To suppress the warning,
	   you need to provide a default case with assert(0) or similar code.

	   This option also warns when a non-volatile automatic variable might
	   be changed by a call to "longjmp".  These warnings as well are
	   possible only in optimizing compilation.

	   The compiler sees only the calls to "setjmp".  It cannot know where
	   "longjmp" will be called; in fact, a signal handler could call it
	   at any point in the code.  As a result, you may get a warning even
	   when there is in fact no problem because "longjmp" cannot in fact
	   be called at the place that would cause a problem.

	   Some spurious warnings can be avoided if you declare all the
	   functions you use that never return as "noreturn".

	   This warning is enabled by -Wall or -Wextra.

       -Wunknown-pragmas
	   Warn when a "#pragma" directive is encountered that is not
	   understood by GCC.  If this command-line option is used, warnings
	   are even issued for unknown pragmas in system header files.	This
	   is not the case if the warnings are only enabled by the -Wall
	   command-line option.

       -Wno-pragmas
	   Do not warn about misuses of pragmas, such as incorrect parameters,
	   invalid syntax, or conflicts between pragmas.  See also
	   -Wunknown-pragmas.

       -Wstrict-aliasing
	   This option is only active when -fstrict-aliasing is active.	 It
	   warns about code that might break the strict aliasing rules that
	   the compiler is using for optimization.  The warning does not catch
	   all cases, but does attempt to catch the more common pitfalls.  It
	   is included in -Wall.  It is equivalent to -Wstrict-aliasing=3

       -Wstrict-aliasing=n
	   This option is only active when -fstrict-aliasing is active.	 It
	   warns about code that might break the strict aliasing rules that
	   the compiler is using for optimization.  Higher levels correspond
	   to higher accuracy (fewer false positives).	Higher levels also
	   correspond to more effort, similar to the way -O works.
	   -Wstrict-aliasing is equivalent to -Wstrict-aliasing=3.

	   Level 1: Most aggressive, quick, least accurate.  Possibly useful
	   when higher levels do not warn but -fstrict-aliasing still breaks
	   the code, as it has very few false negatives.  However, it has many
	   false positives.  Warns for all pointer conversions between
	   possibly incompatible types, even if never dereferenced.  Runs in
	   the front end only.

	   Level 2: Aggressive, quick, not too precise.	 May still have many
	   false positives (not as many as level 1 though), and few false
	   negatives (but possibly more than level 1).	Unlike level 1, it
	   only warns when an address is taken.	 Warns about incomplete types.
	   Runs in the front end only.

	   Level 3 (default for -Wstrict-aliasing): Should have very few false
	   positives and few false negatives.  Slightly slower than levels 1
	   or 2 when optimization is enabled.  Takes care of the common
	   pun+dereference pattern in the front end: "*(int*)&some_float".  If
	   optimization is enabled, it also runs in the back end, where it
	   deals with multiple statement cases using flow-sensitive points-to
	   information.	 Only warns when the converted pointer is
	   dereferenced.  Does not warn about incomplete types.

       -Wstrict-overflow
       -Wstrict-overflow=n
	   This option is only active when -fstrict-overflow is active.	 It
	   warns about cases where the compiler optimizes based on the
	   assumption that signed overflow does not occur.  Note that it does
	   not warn about all cases where the code might overflow: it only
	   warns about cases where the compiler implements some optimization.
	   Thus this warning depends on the optimization level.

	   An optimization that assumes that signed overflow does not occur is
	   perfectly safe if the values of the variables involved are such
	   that overflow never does, in fact, occur.  Therefore this warning
	   can easily give a false positive: a warning about code that is not
	   actually a problem.	To help focus on important issues, several
	   warning levels are defined.	No warnings are issued for the use of
	   undefined signed overflow when estimating how many iterations a
	   loop requires, in particular when determining whether a loop will
	   be executed at all.

	   -Wstrict-overflow=1
	       Warn about cases that are both questionable and easy to avoid.
	       For example,  with -fstrict-overflow, the compiler simplifies
	       "x + 1 > x" to 1.  This level of -Wstrict-overflow is enabled
	       by -Wall; higher levels are not, and must be explicitly
	       requested.

	   -Wstrict-overflow=2
	       Also warn about other cases where a comparison is simplified to
	       a constant.  For example: "abs (x) >= 0".  This can only be
	       simplified when -fstrict-overflow is in effect, because "abs
	       (INT_MIN)" overflows to "INT_MIN", which is less than zero.
	       -Wstrict-overflow (with no level) is the same as
	       -Wstrict-overflow=2.

	   -Wstrict-overflow=3
	       Also warn about other cases where a comparison is simplified.
	       For example: "x + 1 > 1" is simplified to "x > 0".

	   -Wstrict-overflow=4
	       Also warn about other simplifications not covered by the above
	       cases.  For example: "(x * 10) / 5" is simplified to "x * 2".

	   -Wstrict-overflow=5
	       Also warn about cases where the compiler reduces the magnitude
	       of a constant involved in a comparison.	For example: "x + 2 >
	       y" is simplified to "x + 1 >= y".  This is reported only at the
	       highest warning level because this simplification applies to
	       many comparisons, so this warning level gives a very large
	       number of false positives.

       -Wsuggest-attribute=[pure|const|noreturn|format]
	   Warn for cases where adding an attribute may be beneficial. The
	   attributes currently supported are listed below.

	   -Wsuggest-attribute=pure
	   -Wsuggest-attribute=const
	   -Wsuggest-attribute=noreturn
	       Warn about functions that might be candidates for attributes
	       "pure", "const" or "noreturn".  The compiler only warns for
	       functions visible in other compilation units or (in the case of
	       "pure" and "const") if it cannot prove that the function
	       returns normally. A function returns normally if it doesn't
	       contain an infinite loop or return abnormally by throwing,
	       calling "abort()" or trapping.  This analysis requires option
	       -fipa-pure-const, which is enabled by default at -O and higher.
	       Higher optimization levels improve the accuracy of the
	       analysis.

	   -Wsuggest-attribute=format
	   -Wmissing-format-attribute
	       Warn about function pointers that might be candidates for
	       "format" attributes.  Note these are only possible candidates,
	       not absolute ones.  GCC guesses that function pointers with
	       "format" attributes that are used in assignment,
	       initialization, parameter passing or return statements should
	       have a corresponding "format" attribute in the resulting type.
	       I.e. the left-hand side of the assignment or initialization,
	       the type of the parameter variable, or the return type of the
	       containing function respectively should also have a "format"
	       attribute to avoid the warning.

	       GCC also warns about function definitions that might be
	       candidates for "format" attributes.  Again, these are only
	       possible candidates.  GCC guesses that "format" attributes
	       might be appropriate for any function that calls a function
	       like "vprintf" or "vscanf", but this might not always be the
	       case, and some functions for which "format" attributes are
	       appropriate may not be detected.

       -Warray-bounds
	   This option is only active when -ftree-vrp is active (default for
	   -O2 and above). It warns about subscripts to arrays that are always
	   out of bounds. This warning is enabled by -Wall.

       -Wno-div-by-zero
	   Do not warn about compile-time integer division by zero.  Floating-
	   point division by zero is not warned about, as it can be a
	   legitimate way of obtaining infinities and NaNs.

       -Wsystem-headers
	   Print warning messages for constructs found in system header files.
	   Warnings from system headers are normally suppressed, on the
	   assumption that they usually do not indicate real problems and
	   would only make the compiler output harder to read.	Using this
	   command-line option tells GCC to emit warnings from system headers
	   as if they occurred in user code.  However, note that using -Wall
	   in conjunction with this option does not warn about unknown pragmas
	   in system headers---for that, -Wunknown-pragmas must also be used.

       -Wtrampolines
	    Warn about trampolines generated for pointers to nested functions.

	    A trampoline is a small piece of data or code that is created at run
	    time on the stack when the address of a nested function is taken, and
	    is used to call the nested function indirectly.  For some targets, it
	    is made up of data only and thus requires no special treatment.  But,
	    for most targets, it is made up of code and thus requires the stack
	    to be made executable in order for the program to work properly.

       -Wfloat-equal
	   Warn if floating-point values are used in equality comparisons.

	   The idea behind this is that sometimes it is convenient (for the
	   programmer) to consider floating-point values as approximations to
	   infinitely precise real numbers.  If you are doing this, then you
	   need to compute (by analyzing the code, or in some other way) the
	   maximum or likely maximum error that the computation introduces,
	   and allow for it when performing comparisons (and when producing
	   output, but that's a different problem).  In particular, instead of
	   testing for equality, you should check to see whether the two
	   values have ranges that overlap; and this is done with the
	   relational operators, so equality comparisons are probably
	   mistaken.

       -Wtraditional (C and Objective-C only)
	   Warn about certain constructs that behave differently in
	   traditional and ISO C.  Also warn about ISO C constructs that have
	   no traditional C equivalent, and/or problematic constructs that
	   should be avoided.

	   o   Macro parameters that appear within string literals in the
	       macro body.  In traditional C macro replacement takes place
	       within string literals, but in ISO C it does not.

	   o   In traditional C, some preprocessor directives did not exist.
	       Traditional preprocessors only considered a line to be a
	       directive if the # appeared in column 1 on the line.  Therefore
	       -Wtraditional warns about directives that traditional C
	       understands but ignores because the # does not appear as the
	       first character on the line.  It also suggests you hide
	       directives like #pragma not understood by traditional C by
	       indenting them.	Some traditional implementations do not
	       recognize #elif, so this option suggests avoiding it
	       altogether.

	   o   A function-like macro that appears without arguments.

	   o   The unary plus operator.

	   o   The U integer constant suffix, or the F or L floating-point
	       constant suffixes.  (Traditional C does support the L suffix on
	       integer constants.)  Note, these suffixes appear in macros
	       defined in the system headers of most modern systems, e.g. the
	       _MIN/_MAX macros in "<limits.h>".  Use of these macros in user
	       code might normally lead to spurious warnings, however GCC's
	       integrated preprocessor has enough context to avoid warning in
	       these cases.

	   o   A function declared external in one block and then used after
	       the end of the block.

	   o   A "switch" statement has an operand of type "long".

	   o   A non-"static" function declaration follows a "static" one.
	       This construct is not accepted by some traditional C compilers.

	   o   The ISO type of an integer constant has a different width or
	       signedness from its traditional type.  This warning is only
	       issued if the base of the constant is ten.  I.e. hexadecimal or
	       octal values, which typically represent bit patterns, are not
	       warned about.

	   o   Usage of ISO string concatenation is detected.

	   o   Initialization of automatic aggregates.

	   o   Identifier conflicts with labels.  Traditional C lacks a
	       separate namespace for labels.

	   o   Initialization of unions.  If the initializer is zero, the
	       warning is omitted.  This is done under the assumption that the
	       zero initializer in user code appears conditioned on e.g.
	       "__STDC__" to avoid missing initializer warnings and relies on
	       default initialization to zero in the traditional C case.

	   o   Conversions by prototypes between fixed/floating-point values
	       and vice versa.	The absence of these prototypes when compiling
	       with traditional C causes serious problems.  This is a subset
	       of the possible conversion warnings; for the full set use
	       -Wtraditional-conversion.

	   o   Use of ISO C style function definitions.	 This warning
	       intentionally is not issued for prototype declarations or
	       variadic functions because these ISO C features appear in your
	       code when using libiberty's traditional C compatibility macros,
	       "PARAMS" and "VPARAMS".	This warning is also bypassed for
	       nested functions because that feature is already a GCC
	       extension and thus not relevant to traditional C compatibility.

       -Wtraditional-conversion (C and Objective-C only)
	   Warn if a prototype causes a type conversion that is different from
	   what would happen to the same argument in the absence of a
	   prototype.  This includes conversions of fixed point to floating
	   and vice versa, and conversions changing the width or signedness of
	   a fixed-point argument except when the same as the default
	   promotion.

       -Wdeclaration-after-statement (C and Objective-C only)
	   Warn when a declaration is found after a statement in a block.
	   This construct, known from C++, was introduced with ISO C99 and is
	   by default allowed in GCC.  It is not supported by ISO C90 and was
	   not supported by GCC versions before GCC 3.0.

       -Wundef
	   Warn if an undefined identifier is evaluated in an #if directive.

       -Wno-endif-labels
	   Do not warn whenever an #else or an #endif are followed by text.

       -Wshadow
	   Warn whenever a local variable or type declaration shadows another
	   variable, parameter, type, or class member (in C++), or whenever a
	   built-in function is shadowed. Note that in C++, the compiler warns
	   if a local variable shadows an explicit typedef, but not if it
	   shadows a struct/class/enum.

       -Wlarger-than=len
	   Warn whenever an object of larger than len bytes is defined.

       -Wframe-larger-than=len
	   Warn if the size of a function frame is larger than len bytes.  The
	   computation done to determine the stack frame size is approximate
	   and not conservative.  The actual requirements may be somewhat
	   greater than len even if you do not get a warning.  In addition,
	   any space allocated via "alloca", variable-length arrays, or
	   related constructs is not included by the compiler when determining
	   whether or not to issue a warning.

       -Wno-free-nonheap-object
	   Do not warn when attempting to free an object that was not
	   allocated on the heap.

       -Wstack-usage=len
	   Warn if the stack usage of a function might be larger than len
	   bytes.  The computation done to determine the stack usage is
	   conservative.  Any space allocated via "alloca", variable-length
	   arrays, or related constructs is included by the compiler when
	   determining whether or not to issue a warning.

	   The message is in keeping with the output of -fstack-usage.

	   o   If the stack usage is fully static but exceeds the specified
	       amount, it's:

			 warning: stack usage is 1120 bytes

	   o   If the stack usage is (partly) dynamic but bounded, it's:

			 warning: stack usage might be 1648 bytes

	   o   If the stack usage is (partly) dynamic and not bounded, it's:

			 warning: stack usage might be unbounded

       -Wunsafe-loop-optimizations
	   Warn if the loop cannot be optimized because the compiler cannot
	   assume anything on the bounds of the loop indices.  With
	   -funsafe-loop-optimizations warn if the compiler makes such
	   assumptions.

       -Wno-pedantic-ms-format (MinGW targets only)
	   When used in combination with -Wformat and -pedantic without GNU
	   extensions, this option disables the warnings about non-ISO
	   "printf" / "scanf" format width specifiers "I32", "I64", and "I"
	   used on Windows targets, which depend on the MS runtime.

       -Wpointer-arith
	   Warn about anything that depends on the "size of" a function type
	   or of "void".  GNU C assigns these types a size of 1, for
	   convenience in calculations with "void *" pointers and pointers to
	   functions.  In C++, warn also when an arithmetic operation involves
	   "NULL".  This warning is also enabled by -Wpedantic.

       -Wtype-limits
	   Warn if a comparison is always true or always false due to the
	   limited range of the data type, but do not warn for constant
	   expressions.	 For example, warn if an unsigned variable is compared
	   against zero with < or >=.  This warning is also enabled by
	   -Wextra.

       -Wbad-function-cast (C and Objective-C only)
	   Warn whenever a function call is cast to a non-matching type.  For
	   example, warn if "int malloc()" is cast to "anything *".

       -Wc++-compat (C and Objective-C only)
	   Warn about ISO C constructs that are outside of the common subset
	   of ISO C and ISO C++, e.g. request for implicit conversion from
	   "void *" to a pointer to non-"void" type.

       -Wc++11-compat (C++ and Objective-C++ only)
	   Warn about C++ constructs whose meaning differs between ISO C++
	   1998 and ISO C++ 2011, e.g., identifiers in ISO C++ 1998 that are
	   keywords in ISO C++ 2011.  This warning turns on -Wnarrowing and is
	   enabled by -Wall.

       -Wcast-qual
	   Warn whenever a pointer is cast so as to remove a type qualifier
	   from the target type.  For example, warn if a "const char *" is
	   cast to an ordinary "char *".

	   Also warn when making a cast that introduces a type qualifier in an
	   unsafe way.	For example, casting "char **" to "const char **" is
	   unsafe, as in this example:

		     /* p is char ** value.  */
		     const char **q = (const char **) p;
		     /* Assignment of readonly string to const char * is OK.  */
		     *q = "string";
		     /* Now char** pointer points to read-only memory.	*/
		     **p = 'b';

       -Wcast-align
	   Warn whenever a pointer is cast such that the required alignment of
	   the target is increased.  For example, warn if a "char *" is cast
	   to an "int *" on machines where integers can only be accessed at
	   two- or four-byte boundaries.

       -Wwrite-strings
	   When compiling C, give string constants the type "const
	   char[length]" so that copying the address of one into a non-"const"
	   "char *" pointer produces a warning.	 These warnings help you find
	   at compile time code that can try to write into a string constant,
	   but only if you have been very careful about using "const" in
	   declarations and prototypes.	 Otherwise, it is just a nuisance.
	   This is why we did not make -Wall request these warnings.

	   When compiling C++, warn about the deprecated conversion from
	   string literals to "char *".	 This warning is enabled by default
	   for C++ programs.

       -Wclobbered
	   Warn for variables that might be changed by longjmp or vfork.  This
	   warning is also enabled by -Wextra.

       -Wconversion
	   Warn for implicit conversions that may alter a value. This includes
	   conversions between real and integer, like "abs (x)" when "x" is
	   "double"; conversions between signed and unsigned, like "unsigned
	   ui = -1"; and conversions to smaller types, like "sqrtf (M_PI)". Do
	   not warn for explicit casts like "abs ((int) x)" and "ui =
	   (unsigned) -1", or if the value is not changed by the conversion
	   like in "abs (2.0)".	 Warnings about conversions between signed and
	   unsigned integers can be disabled by using -Wno-sign-conversion.

	   For C++, also warn for confusing overload resolution for user-
	   defined conversions; and conversions that never use a type
	   conversion operator: conversions to "void", the same type, a base
	   class or a reference to them. Warnings about conversions between
	   signed and unsigned integers are disabled by default in C++ unless
	   -Wsign-conversion is explicitly enabled.

       -Wno-conversion-null (C++ and Objective-C++ only)
	   Do not warn for conversions between "NULL" and non-pointer types.
	   -Wconversion-null is enabled by default.

       -Wzero-as-null-pointer-constant (C++ and Objective-C++ only)
	   Warn when a literal '0' is used as null pointer constant.  This can
	   be useful to facilitate the conversion to "nullptr" in C++11.

       -Wuseless-cast (C++ and Objective-C++ only)
	   Warn when an expression is casted to its own type.

       -Wempty-body
	   Warn if an empty body occurs in an if, else or do while statement.
	   This warning is also enabled by -Wextra.

       -Wenum-compare
	   Warn about a comparison between values of different enumerated
	   types.  In C++ enumeral mismatches in conditional expressions are
	   also diagnosed and the warning is enabled by default.  In C this
	   warning is enabled by -Wall.

       -Wjump-misses-init (C, Objective-C only)
	   Warn if a "goto" statement or a "switch" statement jumps forward
	   across the initialization of a variable, or jumps backward to a
	   label after the variable has been initialized.  This only warns
	   about variables that are initialized when they are declared.	 This
	   warning is only supported for C and Objective-C; in C++ this sort
	   of branch is an error in any case.

	   -Wjump-misses-init is included in -Wc++-compat.  It can be disabled
	   with the -Wno-jump-misses-init option.

       -Wsign-compare
	   Warn when a comparison between signed and unsigned values could
	   produce an incorrect result when the signed value is converted to
	   unsigned.  This warning is also enabled by -Wextra; to get the
	   other warnings of -Wextra without this warning, use -Wextra
	   -Wno-sign-compare.

       -Wsign-conversion
	   Warn for implicit conversions that may change the sign of an
	   integer value, like assigning a signed integer expression to an
	   unsigned integer variable. An explicit cast silences the warning.
	   In C, this option is enabled also by -Wconversion.

       -Wsizeof-pointer-memaccess
	   Warn for suspicious length parameters to certain string and memory
	   built-in functions if the argument uses "sizeof".  This warning
	   warns e.g.  about "memset (ptr, 0, sizeof (ptr));" if "ptr" is not
	   an array, but a pointer, and suggests a possible fix, or about
	   "memcpy (&foo, ptr, sizeof (&foo));".  This warning is enabled by
	   -Wall.

       -Waddress
	   Warn about suspicious uses of memory addresses. These include using
	   the address of a function in a conditional expression, such as
	   "void func(void); if (func)", and comparisons against the memory
	   address of a string literal, such as "if (x == "abc")".  Such uses
	   typically indicate a programmer error: the address of a function
	   always evaluates to true, so their use in a conditional usually
	   indicate that the programmer forgot the parentheses in a function
	   call; and comparisons against string literals result in unspecified
	   behavior and are not portable in C, so they usually indicate that
	   the programmer intended to use "strcmp".  This warning is enabled
	   by -Wall.

       -Wlogical-op
	   Warn about suspicious uses of logical operators in expressions.
	   This includes using logical operators in contexts where a bit-wise
	   operator is likely to be expected.

       -Waggregate-return
	   Warn if any functions that return structures or unions are defined
	   or called.  (In languages where you can return an array, this also
	   elicits a warning.)

       -Wno-aggressive-loop-optimizations
	   Warn if in a loop with constant number of iterations the compiler
	   detects undefined behavior in some statement during one or more of
	   the iterations.

       -Wno-attributes
	   Do not warn if an unexpected "__attribute__" is used, such as
	   unrecognized attributes, function attributes applied to variables,
	   etc.	 This does not stop errors for incorrect use of supported
	   attributes.

       -Wno-builtin-macro-redefined
	   Do not warn if certain built-in macros are redefined.  This
	   suppresses warnings for redefinition of "__TIMESTAMP__",
	   "__TIME__", "__DATE__", "__FILE__", and "__BASE_FILE__".

       -Wstrict-prototypes (C and Objective-C only)
	   Warn if a function is declared or defined without specifying the
	   argument types.  (An old-style function definition is permitted
	   without a warning if preceded by a declaration that specifies the
	   argument types.)

       -Wold-style-declaration (C and Objective-C only)
	   Warn for obsolescent usages, according to the C Standard, in a
	   declaration. For example, warn if storage-class specifiers like
	   "static" are not the first things in a declaration.	This warning
	   is also enabled by -Wextra.

       -Wold-style-definition (C and Objective-C only)
	   Warn if an old-style function definition is used.  A warning is
	   given even if there is a previous prototype.

       -Wmissing-parameter-type (C and Objective-C only)
	   A function parameter is declared without a type specifier in
	   K&R-style functions:

		   void foo(bar) { }

	   This warning is also enabled by -Wextra.

       -Wmissing-prototypes (C and Objective-C only)
	   Warn if a global function is defined without a previous prototype
	   declaration.	 This warning is issued even if the definition itself
	   provides a prototype.  Use this option to detect global functions
	   that do not have a matching prototype declaration in a header file.
	   This option is not valid for C++ because all function declarations
	   provide prototypes and a non-matching declaration will declare an
	   overload rather than conflict with an earlier declaration.  Use
	   -Wmissing-declarations to detect missing declarations in C++.

       -Wmissing-declarations
	   Warn if a global function is defined without a previous
	   declaration.	 Do so even if the definition itself provides a
	   prototype.  Use this option to detect global functions that are not
	   declared in header files.  In C, no warnings are issued for
	   functions with previous non-prototype declarations; use
	   -Wmissing-prototype to detect missing prototypes.  In C++, no
	   warnings are issued for function templates, or for inline
	   functions, or for functions in anonymous namespaces.

       -Wmissing-field-initializers
	   Warn if a structure's initializer has some fields missing.  For
	   example, the following code causes such a warning, because "x.h" is
	   implicitly zero:

		   struct s { int f, g, h; };
		   struct s x = { 3, 4 };

	   This option does not warn about designated initializers, so the
	   following modification does not trigger a warning:

		   struct s { int f, g, h; };
		   struct s x = { .f = 3, .g = 4 };

	   This warning is included in -Wextra.	 To get other -Wextra warnings
	   without this one, use -Wextra -Wno-missing-field-initializers.

       -Wno-multichar
	   Do not warn if a multicharacter constant ('FOOF') is used.  Usually
	   they indicate a typo in the user's code, as they have
	   implementation-defined values, and should not be used in portable
	   code.

       -Wnormalized=<none|id|nfc|nfkc>
	   In ISO C and ISO C++, two identifiers are different if they are
	   different sequences of characters.  However, sometimes when
	   characters outside the basic ASCII character set are used, you can
	   have two different character sequences that look the same.  To
	   avoid confusion, the ISO 10646 standard sets out some normalization
	   rules which when applied ensure that two sequences that look the
	   same are turned into the same sequence.  GCC can warn you if you
	   are using identifiers that have not been normalized; this option
	   controls that warning.

	   There are four levels of warning supported by GCC.  The default is
	   -Wnormalized=nfc, which warns about any identifier that is not in
	   the ISO 10646 "C" normalized form, NFC.  NFC is the recommended
	   form for most uses.

	   Unfortunately, there are some characters allowed in identifiers by
	   ISO C and ISO C++ that, when turned into NFC, are not allowed in
	   identifiers.	 That is, there's no way to use these symbols in
	   portable ISO C or C++ and have all your identifiers in NFC.
	   -Wnormalized=id suppresses the warning for these characters.	 It is
	   hoped that future versions of the standards involved will correct
	   this, which is why this option is not the default.

	   You can switch the warning off for all characters by writing
	   -Wnormalized=none.  You should only do this if you are using some
	   other normalization scheme (like "D"), because otherwise you can
	   easily create bugs that are literally impossible to see.

	   Some characters in ISO 10646 have distinct meanings but look
	   identical in some fonts or display methodologies, especially once
	   formatting has been applied.	 For instance "\u207F", "SUPERSCRIPT
	   LATIN SMALL LETTER N", displays just like a regular "n" that has
	   been placed in a superscript.  ISO 10646 defines the NFKC
	   normalization scheme to convert all these into a standard form as
	   well, and GCC warns if your code is not in NFKC if you use
	   -Wnormalized=nfkc.  This warning is comparable to warning about
	   every identifier that contains the letter O because it might be
	   confused with the digit 0, and so is not the default, but may be
	   useful as a local coding convention if the programming environment
	   cannot be fixed to display these characters distinctly.

       -Wno-deprecated
	   Do not warn about usage of deprecated features.

       -Wno-deprecated-declarations
	   Do not warn about uses of functions, variables, and types marked as
	   deprecated by using the "deprecated" attribute.

       -Wno-overflow
	   Do not warn about compile-time overflow in constant expressions.

       -Woverride-init (C and Objective-C only)
	   Warn if an initialized field without side effects is overridden
	   when using designated initializers.

	   This warning is included in -Wextra.	 To get other -Wextra warnings
	   without this one, use -Wextra -Wno-override-init.

       -Wpacked
	   Warn if a structure is given the packed attribute, but the packed
	   attribute has no effect on the layout or size of the structure.
	   Such structures may be mis-aligned for little benefit.  For
	   instance, in this code, the variable "f.x" in "struct bar" is
	   misaligned even though "struct bar" does not itself have the packed
	   attribute:

		   struct foo {
		     int x;
		     char a, b, c, d;
		   } __attribute__((packed));
		   struct bar {
		     char z;
		     struct foo f;
		   };

       -Wpacked-bitfield-compat
	   The 4.1, 4.2 and 4.3 series of GCC ignore the "packed" attribute on
	   bit-fields of type "char".  This has been fixed in GCC 4.4 but the
	   change can lead to differences in the structure layout.  GCC
	   informs you when the offset of such a field has changed in GCC 4.4.
	   For example there is no longer a 4-bit padding between field "a"
	   and "b" in this structure:

		   struct foo
		   {
		     char a:4;
		     char b:8;
		   } __attribute__ ((packed));

	   This warning is enabled by default.	Use
	   -Wno-packed-bitfield-compat to disable this warning.

       -Wpadded
	   Warn if padding is included in a structure, either to align an
	   element of the structure or to align the whole structure.
	   Sometimes when this happens it is possible to rearrange the fields
	   of the structure to reduce the padding and so make the structure
	   smaller.

       -Wredundant-decls
	   Warn if anything is declared more than once in the same scope, even
	   in cases where multiple declaration is valid and changes nothing.

       -Wnested-externs (C and Objective-C only)
	   Warn if an "extern" declaration is encountered within a function.

       -Wno-inherited-variadic-ctor
	   Suppress warnings about use of C++11 inheriting constructors when
	   the base class inherited from has a C variadic constructor; the
	   warning is on by default because the ellipsis is not inherited.

       -Winline
	   Warn if a function that is declared as inline cannot be inlined.
	   Even with this option, the compiler does not warn about failures to
	   inline functions declared in system headers.

	   The compiler uses a variety of heuristics to determine whether or
	   not to inline a function.  For example, the compiler takes into
	   account the size of the function being inlined and the amount of
	   inlining that has already been done in the current function.
	   Therefore, seemingly insignificant changes in the source program
	   can cause the warnings produced by -Winline to appear or disappear.

       -Wno-invalid-offsetof (C++ and Objective-C++ only)
	   Suppress warnings from applying the offsetof macro to a non-POD
	   type.  According to the 1998 ISO C++ standard, applying offsetof to
	   a non-POD type is undefined.	 In existing C++ implementations,
	   however, offsetof typically gives meaningful results even when
	   applied to certain kinds of non-POD types (such as a simple struct
	   that fails to be a POD type only by virtue of having a
	   constructor).  This flag is for users who are aware that they are
	   writing nonportable code and who have deliberately chosen to ignore
	   the warning about it.

	   The restrictions on offsetof may be relaxed in a future version of
	   the C++ standard.

       -Wno-int-to-pointer-cast
	   Suppress warnings from casts to pointer type of an integer of a
	   different size. In C++, casting to a pointer type of smaller size
	   is an error. Wint-to-pointer-cast is enabled by default.

       -Wno-pointer-to-int-cast (C and Objective-C only)
	   Suppress warnings from casts from a pointer to an integer type of a
	   different size.

       -Winvalid-pch
	   Warn if a precompiled header is found in the search path but can't
	   be used.

       -Wlong-long
	   Warn if long long type is used.  This is enabled by either
	   -Wpedantic or -Wtraditional in ISO C90 and C++98 modes.  To inhibit
	   the warning messages, use -Wno-long-long.

       -Wvariadic-macros
	   Warn if variadic macros are used in pedantic ISO C90 mode, or the
	   GNU alternate syntax when in pedantic ISO C99 mode.	This is
	   default.  To inhibit the warning messages, use
	   -Wno-variadic-macros.

       -Wvarargs
	   Warn upon questionable usage of the macros used to handle variable
	   arguments like va_start.  This is default.  To inhibit the warning
	   messages, use -Wno-varargs.

       -Wvector-operation-performance
	   Warn if vector operation is not implemented via SIMD capabilities
	   of the architecture.	 Mainly useful for the performance tuning.
	   Vector operation can be implemented "piecewise", which means that
	   the scalar operation is performed on every vector element; "in
	   parallel", which means that the vector operation is implemented
	   using scalars of wider type, which normally is more performance
	   efficient; and "as a single scalar", which means that vector fits
	   into a scalar type.

       -Wno-virtual-move-assign
	   Suppress warnings about inheriting from a virtual base with a non-
	   trivial C++11 move assignment operator.  This is dangerous because
	   if the virtual base is reachable along more than one path, it will
	   be moved multiple times, which can mean both objects end up in the
	   moved-from state.  If the move assignment operator is written to
	   avoid moving from a moved-from object, this warning can be
	   disabled.

       -Wvla
	   Warn if variable length array is used in the code.  -Wno-vla
	   prevents the -Wpedantic warning of the variable length array.

       -Wvolatile-register-var
	   Warn if a register variable is declared volatile.  The volatile
	   modifier does not inhibit all optimizations that may eliminate
	   reads and/or writes to register variables.  This warning is enabled
	   by -Wall.

       -Wdisabled-optimization
	   Warn if a requested optimization pass is disabled.  This warning
	   does not generally indicate that there is anything wrong with your
	   code; it merely indicates that GCC's optimizers are unable to
	   handle the code effectively.	 Often, the problem is that your code
	   is too big or too complex; GCC refuses to optimize programs when
	   the optimization itself is likely to take inordinate amounts of
	   time.

       -Wpointer-sign (C and Objective-C only)
	   Warn for pointer argument passing or assignment with different
	   signedness.	This option is only supported for C and Objective-C.
	   It is implied by -Wall and by -Wpedantic, which can be disabled
	   with -Wno-pointer-sign.

       -Wstack-protector
	   This option is only active when -fstack-protector is active.	 It
	   warns about functions that are not protected against stack
	   smashing.

       -Wno-mudflap
	   Suppress warnings about constructs that cannot be instrumented by
	   -fmudflap.

       -Woverlength-strings
	   Warn about string constants that are longer than the "minimum
	   maximum" length specified in the C standard.	 Modern compilers
	   generally allow string constants that are much longer than the
	   standard's minimum limit, but very portable programs should avoid
	   using longer strings.

	   The limit applies after string constant concatenation, and does not
	   count the trailing NUL.  In C90, the limit was 509 characters; in
	   C99, it was raised to 4095.	C++98 does not specify a normative
	   minimum maximum, so we do not diagnose overlength strings in C++.

	   This option is implied by -Wpedantic, and can be disabled with
	   -Wno-overlength-strings.

       -Wunsuffixed-float-constants (C and Objective-C only)
	   Issue a warning for any floating constant that does not have a
	   suffix.  When used together with -Wsystem-headers it warns about
	   such constants in system header files.  This can be useful when
	   preparing code to use with the "FLOAT_CONST_DECIMAL64" pragma from
	   the decimal floating-point extension to C99.

   Options for Debugging Your Program or GCC
       GCC has various special options that are used for debugging either your
       program or GCC:

       -g  Produce debugging information in the operating system's native
	   format (stabs, COFF, XCOFF, or DWARF 2).  GDB can work with this
	   debugging information.

	   On most systems that use stabs format, -g enables use of extra
	   debugging information that only GDB can use; this extra information
	   makes debugging work better in GDB but probably makes other
	   debuggers crash or refuse to read the program.  If you want to
	   control for certain whether to generate the extra information, use
	   -gstabs+, -gstabs, -gxcoff+, -gxcoff, or -gvms (see below).

	   GCC allows you to use -g with -O.  The shortcuts taken by optimized
	   code may occasionally produce surprising results: some variables
	   you declared may not exist at all; flow of control may briefly move
	   where you did not expect it; some statements may not be executed
	   because they compute constant results or their values are already
	   at hand; some statements may execute in different places because
	   they have been moved out of loops.

	   Nevertheless it proves possible to debug optimized output.  This
	   makes it reasonable to use the optimizer for programs that might
	   have bugs.

	   The following options are useful when GCC is generated with the
	   capability for more than one debugging format.

       -gsplit-dwarf
	   Separate as much dwarf debugging information as possible into a
	   separate output file with the extension .dwo.  This option allows
	   the build system to avoid linking files with debug information.  To
	   be useful, this option requires a debugger capable of reading .dwo
	   files.

       -ggdb
	   Produce debugging information for use by GDB.  This means to use
	   the most expressive format available (DWARF 2, stabs, or the native
	   format if neither of those are supported), including GDB extensions
	   if at all possible.

       -gpubnames
	   Generate dwarf .debug_pubnames and .debug_pubtypes sections.

       -gstabs
	   Produce debugging information in stabs format (if that is
	   supported), without GDB extensions.	This is the format used by DBX
	   on most BSD systems.	 On MIPS, Alpha and System V Release 4 systems
	   this option produces stabs debugging output that is not understood
	   by DBX or SDB.  On System V Release 4 systems this option requires
	   the GNU assembler.

       -feliminate-unused-debug-symbols
	   Produce debugging information in stabs format (if that is
	   supported), for only symbols that are actually used.

       -femit-class-debug-always
	   Instead of emitting debugging information for a C++ class in only
	   one object file, emit it in all object files using the class.  This
	   option should be used only with debuggers that are unable to handle
	   the way GCC normally emits debugging information for classes
	   because using this option increases the size of debugging
	   information by as much as a factor of two.

       -fdebug-types-section
	   When using DWARF Version 4 or higher, type DIEs can be put into
	   their own ".debug_types" section instead of making them part of the
	   ".debug_info" section.  It is more efficient to put them in a
	   separate comdat sections since the linker can then remove
	   duplicates.	But not all DWARF consumers support ".debug_types"
	   sections yet and on some objects ".debug_types" produces larger
	   instead of smaller debugging information.

       -gstabs+
	   Produce debugging information in stabs format (if that is
	   supported), using GNU extensions understood only by the GNU
	   debugger (GDB).  The use of these extensions is likely to make
	   other debuggers crash or refuse to read the program.

       -gcoff
	   Produce debugging information in COFF format (if that is
	   supported).	This is the format used by SDB on most System V
	   systems prior to System V Release 4.

       -gxcoff
	   Produce debugging information in XCOFF format (if that is
	   supported).	This is the format used by the DBX debugger on IBM
	   RS/6000 systems.

       -gxcoff+
	   Produce debugging information in XCOFF format (if that is
	   supported), using GNU extensions understood only by the GNU
	   debugger (GDB).  The use of these extensions is likely to make
	   other debuggers crash or refuse to read the program, and may cause
	   assemblers other than the GNU assembler (GAS) to fail with an
	   error.

       -gdwarf-version
	   Produce debugging information in DWARF format (if that is
	   supported).	The value of version may be either 2, 3 or 4; the
	   default version for most targets is 4.

	   Note that with DWARF Version 2, some ports require and always use
	   some non-conflicting DWARF 3 extensions in the unwind tables.

	   Version 4 may require GDB 7.0 and -fvar-tracking-assignments for
	   maximum benefit.

       -grecord-gcc-switches
	   This switch causes the command-line options used to invoke the
	   compiler that may affect code generation to be appended to the
	   DW_AT_producer attribute in DWARF debugging information.  The
	   options are concatenated with spaces separating them from each
	   other and from the compiler version.	 See also
	   -frecord-gcc-switches for another way of storing compiler options
	   into the object file.  This is the default.

       -gno-record-gcc-switches
	   Disallow appending command-line options to the DW_AT_producer
	   attribute in DWARF debugging information.

       -gstrict-dwarf
	   Disallow using extensions of later DWARF standard version than
	   selected with -gdwarf-version.  On most targets using non-
	   conflicting DWARF extensions from later standard versions is
	   allowed.

       -gno-strict-dwarf
	   Allow using extensions of later DWARF standard version than
	   selected with -gdwarf-version.

       -gvms
	   Produce debugging information in Alpha/VMS debug format (if that is
	   supported).	This is the format used by DEBUG on Alpha/VMS systems.

       -glevel
       -ggdblevel
       -gstabslevel
       -gcofflevel
       -gxcofflevel
       -gvmslevel
	   Request debugging information and also use level to specify how
	   much information.  The default level is 2.

	   Level 0 produces no debug information at all.  Thus, -g0 negates
	   -g.

	   Level 1 produces minimal information, enough for making backtraces
	   in parts of the program that you don't plan to debug.  This
	   includes descriptions of functions and external variables, but no
	   information about local variables and no line numbers.

	   Level 3 includes extra information, such as all the macro
	   definitions present in the program.	Some debuggers support macro
	   expansion when you use -g3.

	   -gdwarf-2 does not accept a concatenated debug level, because GCC
	   used to support an option -gdwarf that meant to generate debug
	   information in version 1 of the DWARF format (which is very
	   different from version 2), and it would have been too confusing.
	   That debug format is long obsolete, but the option cannot be
	   changed now.	 Instead use an additional -glevel option to change
	   the debug level for DWARF.

       -gtoggle
	   Turn off generation of debug info, if leaving out this option
	   generates it, or turn it on at level 2 otherwise.  The position of
	   this argument in the command line does not matter; it takes effect
	   after all other options are processed, and it does so only once, no
	   matter how many times it is given.  This is mainly intended to be
	   used with -fcompare-debug.

       -fsanitize=address
	   Enable AddressSanitizer, a fast memory error detector.  Memory
	   access instructions will be instrumented to detect out-of-bounds
	   and use-after-free bugs.  See
	   <http://code.google.com/p/address-sanitizer/> for more details.

       -fsanitize=thread
	   Enable ThreadSanitizer, a fast data race detector.  Memory access
	   instructions will be instrumented to detect data race bugs.	See
	   <http://code.google.com/p/data-race-test/wiki/ThreadSanitizer> for
	   more details.

       -fdump-final-insns[=file]
	   Dump the final internal representation (RTL) to file.  If the
	   optional argument is omitted (or if file is "."), the name of the
	   dump file is determined by appending ".gkd" to the compilation
	   output file name.

       -fcompare-debug[=opts]
	   If no error occurs during compilation, run the compiler a second
	   time, adding opts and -fcompare-debug-second to the arguments
	   passed to the second compilation.  Dump the final internal
	   representation in both compilations, and print an error if they
	   differ.

	   If the equal sign is omitted, the default -gtoggle is used.

	   The environment variable GCC_COMPARE_DEBUG, if defined, non-empty
	   and nonzero, implicitly enables -fcompare-debug.  If
	   GCC_COMPARE_DEBUG is defined to a string starting with a dash, then
	   it is used for opts, otherwise the default -gtoggle is used.

	   -fcompare-debug=, with the equal sign but without opts, is
	   equivalent to -fno-compare-debug, which disables the dumping of the
	   final representation and the second compilation, preventing even
	   GCC_COMPARE_DEBUG from taking effect.

	   To verify full coverage during -fcompare-debug testing, set
	   GCC_COMPARE_DEBUG to say -fcompare-debug-not-overridden, which GCC
	   rejects as an invalid option in any actual compilation (rather than
	   preprocessing, assembly or linking).	 To get just a warning,
	   setting GCC_COMPARE_DEBUG to -w%n-fcompare-debug not overridden
	   will do.

       -fcompare-debug-second
	   This option is implicitly passed to the compiler for the second
	   compilation requested by -fcompare-debug, along with options to
	   silence warnings, and omitting other options that would cause side-
	   effect compiler outputs to files or to the standard output.	Dump
	   files and preserved temporary files are renamed so as to contain
	   the ".gk" additional extension during the second compilation, to
	   avoid overwriting those generated by the first.

	   When this option is passed to the compiler driver, it causes the
	   first compilation to be skipped, which makes it useful for little
	   other than debugging the compiler proper.

       -feliminate-dwarf2-dups
	   Compress DWARF 2 debugging information by eliminating duplicated
	   information about each symbol.  This option only makes sense when
	   generating DWARF 2 debugging information with -gdwarf-2.

       -femit-struct-debug-baseonly
	   Emit debug information for struct-like types only when the base
	   name of the compilation source file matches the base name of file
	   in which the struct is defined.

	   This option substantially reduces the size of debugging
	   information, but at significant potential loss in type information
	   to the debugger.  See -femit-struct-debug-reduced for a less
	   aggressive option.  See -femit-struct-debug-detailed for more
	   detailed control.

	   This option works only with DWARF 2.

       -femit-struct-debug-reduced
	   Emit debug information for struct-like types only when the base
	   name of the compilation source file matches the base name of file
	   in which the type is defined, unless the struct is a template or
	   defined in a system header.

	   This option significantly reduces the size of debugging
	   information, with some potential loss in type information to the
	   debugger.  See -femit-struct-debug-baseonly for a more aggressive
	   option.  See -femit-struct-debug-detailed for more detailed
	   control.

	   This option works only with DWARF 2.

       -femit-struct-debug-detailed[=spec-list]
	   Specify the struct-like types for which the compiler generates
	   debug information.  The intent is to reduce duplicate struct debug
	   information between different object files within the same program.

	   This option is a detailed version of -femit-struct-debug-reduced
	   and -femit-struct-debug-baseonly, which serves for most needs.

	   A specification has the
	   syntax[dir:|ind:][ord:|gen:](any|sys|base|none)

	   The optional first word limits the specification to structs that
	   are used directly (dir:) or used indirectly (ind:).	A struct type
	   is used directly when it is the type of a variable, member.
	   Indirect uses arise through pointers to structs.  That is, when use
	   of an incomplete struct is valid, the use is indirect.  An example
	   is struct one direct; struct two * indirect;.

	   The optional second word limits the specification to ordinary
	   structs (ord:) or generic structs (gen:).  Generic structs are a
	   bit complicated to explain.	For C++, these are non-explicit
	   specializations of template classes, or non-template classes within
	   the above.  Other programming languages have generics, but
	   -femit-struct-debug-detailed does not yet implement them.

	   The third word specifies the source files for those structs for
	   which the compiler should emit debug information.  The values none
	   and any have the normal meaning.  The value base means that the
	   base of name of the file in which the type declaration appears must
	   match the base of the name of the main compilation file.  In
	   practice, this means that when compiling foo.c, debug information
	   is generated for types declared in that file and foo.h, but not
	   other header files.	The value sys means those types satisfying
	   base or declared in system or compiler headers.

	   You may need to experiment to determine the best settings for your
	   application.

	   The default is -femit-struct-debug-detailed=all.

	   This option works only with DWARF 2.

       -fno-merge-debug-strings
	   Direct the linker to not merge together strings in the debugging
	   information that are identical in different object files.  Merging
	   is not supported by all assemblers or linkers.  Merging decreases
	   the size of the debug information in the output file at the cost of
	   increasing link processing time.  Merging is enabled by default.

       -fdebug-prefix-map=old=new
	   When compiling files in directory old, record debugging information
	   describing them as in new instead.

       -fno-dwarf2-cfi-asm
	   Emit DWARF 2 unwind info as compiler generated ".eh_frame" section
	   instead of using GAS ".cfi_*" directives.

       -p  Generate extra code to write profile information suitable for the
	   analysis program prof.  You must use this option when compiling the
	   source files you want data about, and you must also use it when
	   linking.

       -pg Generate extra code to write profile information suitable for the
	   analysis program gprof.  You must use this option when compiling
	   the source files you want data about, and you must also use it when
	   linking.

       -Q  Makes the compiler print out each function name as it is compiled,
	   and print some statistics about each pass when it finishes.

       -ftime-report
	   Makes the compiler print some statistics about the time consumed by
	   each pass when it finishes.

       -fmem-report
	   Makes the compiler print some statistics about permanent memory
	   allocation when it finishes.

       -fmem-report-wpa
	   Makes the compiler print some statistics about permanent memory
	   allocation for the WPA phase only.

       -fpre-ipa-mem-report
       -fpost-ipa-mem-report
	   Makes the compiler print some statistics about permanent memory
	   allocation before or after interprocedural optimization.

       -fprofile-report
	   Makes the compiler print some statistics about consistency of the
	   (estimated) profile and effect of individual passes.

       -fstack-usage
	   Makes the compiler output stack usage information for the program,
	   on a per-function basis.  The filename for the dump is made by
	   appending .su to the auxname.  auxname is generated from the name
	   of the output file, if explicitly specified and it is not an
	   executable, otherwise it is the basename of the source file.	 An
	   entry is made up of three fields:

	   o   The name of the function.

	   o   A number of bytes.

	   o   One or more qualifiers: "static", "dynamic", "bounded".

	   The qualifier "static" means that the function manipulates the
	   stack statically: a fixed number of bytes are allocated for the
	   frame on function entry and released on function exit; no stack
	   adjustments are otherwise made in the function.  The second field
	   is this fixed number of bytes.

	   The qualifier "dynamic" means that the function manipulates the
	   stack dynamically: in addition to the static allocation described
	   above, stack adjustments are made in the body of the function, for
	   example to push/pop arguments around function calls.	 If the
	   qualifier "bounded" is also present, the amount of these
	   adjustments is bounded at compile time and the second field is an
	   upper bound of the total amount of stack used by the function.  If
	   it is not present, the amount of these adjustments is not bounded
	   at compile time and the second field only represents the bounded
	   part.

       -fprofile-arcs
	   Add code so that program flow arcs are instrumented.	 During
	   execution the program records how many times each branch and call
	   is executed and how many times it is taken or returns.  When the
	   compiled program exits it saves this data to a file called
	   auxname.gcda for each source file.  The data may be used for
	   profile-directed optimizations (-fbranch-probabilities), or for
	   test coverage analysis (-ftest-coverage).  Each object file's
	   auxname is generated from the name of the output file, if
	   explicitly specified and it is not the final executable, otherwise
	   it is the basename of the source file.  In both cases any suffix is
	   removed (e.g. foo.gcda for input file dir/foo.c, or dir/foo.gcda
	   for output file specified as -o dir/foo.o).

       --coverage
	   This option is used to compile and link code instrumented for
	   coverage analysis.  The option is a synonym for -fprofile-arcs
	   -ftest-coverage (when compiling) and -lgcov (when linking).	See
	   the documentation for those options for more details.

	   o   Compile the source files with -fprofile-arcs plus optimization
	       and code generation options.  For test coverage analysis, use
	       the additional -ftest-coverage option.  You do not need to
	       profile every source file in a program.

	   o   Link your object files with -lgcov or -fprofile-arcs (the
	       latter implies the former).

	   o   Run the program on a representative workload to generate the
	       arc profile information.	 This may be repeated any number of
	       times.  You can run concurrent instances of your program, and
	       provided that the file system supports locking, the data files
	       will be correctly updated.  Also "fork" calls are detected and
	       correctly handled (double counting will not happen).

	   o   For profile-directed optimizations, compile the source files
	       again with the same optimization and code generation options
	       plus -fbranch-probabilities.

	   o   For test coverage analysis, use gcov to produce human readable
	       information from the .gcno and .gcda files.  Refer to the gcov
	       documentation for further information.

	   With -fprofile-arcs, for each function of your program GCC creates
	   a program flow graph, then finds a spanning tree for the graph.
	   Only arcs that are not on the spanning tree have to be
	   instrumented: the compiler adds code to count the number of times
	   that these arcs are executed.  When an arc is the only exit or only
	   entrance to a block, the instrumentation code can be added to the
	   block; otherwise, a new basic block must be created to hold the
	   instrumentation code.

       -ftest-coverage
	   Produce a notes file that the gcov code-coverage utility can use to
	   show program coverage.  Each source file's note file is called
	   auxname.gcno.  Refer to the -fprofile-arcs option above for a
	   description of auxname and instructions on how to generate test
	   coverage data.  Coverage data matches the source files more closely
	   if you do not optimize.

       -fdbg-cnt-list
	   Print the name and the counter upper bound for all debug counters.

       -fdbg-cnt=counter-value-list
	   Set the internal debug counter upper bound.	counter-value-list is
	   a comma-separated list of name:value pairs which sets the upper
	   bound of each debug counter name to value.  All debug counters have
	   the initial upper bound of "UINT_MAX"; thus "dbg_cnt()" returns
	   true always unless the upper bound is set by this option.  For
	   example, with -fdbg-cnt=dce:10,tail_call:0, "dbg_cnt(dce)" returns
	   true only for first 10 invocations.

       -fenable-kind-pass
       -fdisable-kind-pass=range-list
	   This is a set of options that are used to explicitly disable/enable
	   optimization passes.	 These options are intended for use for
	   debugging GCC.  Compiler users should use regular options for
	   enabling/disabling passes instead.

	   -fdisable-ipa-pass
	       Disable IPA pass pass. pass is the pass name.  If the same pass
	       is statically invoked in the compiler multiple times, the pass
	       name should be appended with a sequential number starting from
	       1.

	   -fdisable-rtl-pass
	   -fdisable-rtl-pass=range-list
	       Disable RTL pass pass.  pass is the pass name.  If the same
	       pass is statically invoked in the compiler multiple times, the
	       pass name should be appended with a sequential number starting
	       from 1.	range-list is a comma-separated list of function
	       ranges or assembler names.  Each range is a number pair
	       separated by a colon.  The range is inclusive in both ends.  If
	       the range is trivial, the number pair can be simplified as a
	       single number.  If the function's call graph node's uid falls
	       within one of the specified ranges, the pass is disabled for
	       that function.  The uid is shown in the function header of a
	       dump file, and the pass names can be dumped by using option
	       -fdump-passes.

	   -fdisable-tree-pass
	   -fdisable-tree-pass=range-list
	       Disable tree pass pass.	See -fdisable-rtl for the description
	       of option arguments.

	   -fenable-ipa-pass
	       Enable IPA pass pass.  pass is the pass name.  If the same pass
	       is statically invoked in the compiler multiple times, the pass
	       name should be appended with a sequential number starting from
	       1.

	   -fenable-rtl-pass
	   -fenable-rtl-pass=range-list
	       Enable RTL pass pass.  See -fdisable-rtl for option argument
	       description and examples.

	   -fenable-tree-pass
	   -fenable-tree-pass=range-list
	       Enable tree pass pass.  See -fdisable-rtl for the description
	       of option arguments.

	   Here are some examples showing uses of these options.

		   # disable ccp1 for all functions
		      -fdisable-tree-ccp1
		   # disable complete unroll for function whose cgraph node uid is 1
		      -fenable-tree-cunroll=1
		   # disable gcse2 for functions at the following ranges [1,1],
		   # [300,400], and [400,1000]
		   # disable gcse2 for functions foo and foo2
		      -fdisable-rtl-gcse2=foo,foo2
		   # disable early inlining
		      -fdisable-tree-einline
		   # disable ipa inlining
		      -fdisable-ipa-inline
		   # enable tree full unroll
		      -fenable-tree-unroll

       -dletters
       -fdump-rtl-pass
       -fdump-rtl-pass=filename
	   Says to make debugging dumps during compilation at times specified
	   by letters.	This is used for debugging the RTL-based passes of the
	   compiler.  The file names for most of the dumps are made by
	   appending a pass number and a word to the dumpname, and the files
	   are created in the directory of the output file. In case of
	   =filename option, the dump is output on the given file instead of
	   the pass numbered dump files. Note that the pass number is computed
	   statically as passes get registered into the pass manager.  Thus
	   the numbering is not related to the dynamic order of execution of
	   passes.  In particular, a pass installed by a plugin could have a
	   number over 200 even if it executed quite early.  dumpname is
	   generated from the name of the output file, if explicitly specified
	   and it is not an executable, otherwise it is the basename of the
	   source file. These switches may have different effects when -E is
	   used for preprocessing.

	   Debug dumps can be enabled with a -fdump-rtl switch or some -d
	   option letters.  Here are the possible letters for use in pass and
	   letters, and their meanings:

	   -fdump-rtl-alignments
	       Dump after branch alignments have been computed.

	   -fdump-rtl-asmcons
	       Dump after fixing rtl statements that have unsatisfied in/out
	       constraints.

	   -fdump-rtl-auto_inc_dec
	       Dump after auto-inc-dec discovery.  This pass is only run on
	       architectures that have auto inc or auto dec instructions.

	   -fdump-rtl-barriers
	       Dump after cleaning up the barrier instructions.

	   -fdump-rtl-bbpart
	       Dump after partitioning hot and cold basic blocks.

	   -fdump-rtl-bbro
	       Dump after block reordering.

	   -fdump-rtl-btl1
	   -fdump-rtl-btl2
	       -fdump-rtl-btl1 and -fdump-rtl-btl2 enable dumping after the
	       two branch target load optimization passes.

	   -fdump-rtl-bypass
	       Dump after jump bypassing and control flow optimizations.

	   -fdump-rtl-combine
	       Dump after the RTL instruction combination pass.

	   -fdump-rtl-compgotos
	       Dump after duplicating the computed gotos.

	   -fdump-rtl-ce1
	   -fdump-rtl-ce2
	   -fdump-rtl-ce3
	       -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3 enable
	       dumping after the three if conversion passes.

	   -fdump-rtl-cprop_hardreg
	       Dump after hard register copy propagation.

	   -fdump-rtl-csa
	       Dump after combining stack adjustments.

	   -fdump-rtl-cse1
	   -fdump-rtl-cse2
	       -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping after the
	       two common subexpression elimination passes.

	   -fdump-rtl-dce
	       Dump after the standalone dead code elimination passes.

	   -fdump-rtl-dbr
	       Dump after delayed branch scheduling.

	   -fdump-rtl-dce1
	   -fdump-rtl-dce2
	       -fdump-rtl-dce1 and -fdump-rtl-dce2 enable dumping after the
	       two dead store elimination passes.

	   -fdump-rtl-eh
	       Dump after finalization of EH handling code.

	   -fdump-rtl-eh_ranges
	       Dump after conversion of EH handling range regions.

	   -fdump-rtl-expand
	       Dump after RTL generation.

	   -fdump-rtl-fwprop1
	   -fdump-rtl-fwprop2
	       -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable dumping after
	       the two forward propagation passes.

	   -fdump-rtl-gcse1
	   -fdump-rtl-gcse2
	       -fdump-rtl-gcse1 and -fdump-rtl-gcse2 enable dumping after
	       global common subexpression elimination.

	   -fdump-rtl-init-regs
	       Dump after the initialization of the registers.

	   -fdump-rtl-initvals
	       Dump after the computation of the initial value sets.

	   -fdump-rtl-into_cfglayout
	       Dump after converting to cfglayout mode.

	   -fdump-rtl-ira
	       Dump after iterated register allocation.

	   -fdump-rtl-jump
	       Dump after the second jump optimization.

	   -fdump-rtl-loop2
	       -fdump-rtl-loop2 enables dumping after the rtl loop
	       optimization passes.

	   -fdump-rtl-mach
	       Dump after performing the machine dependent reorganization
	       pass, if that pass exists.

	   -fdump-rtl-mode_sw
	       Dump after removing redundant mode switches.

	   -fdump-rtl-rnreg
	       Dump after register renumbering.

	   -fdump-rtl-outof_cfglayout
	       Dump after converting from cfglayout mode.

	   -fdump-rtl-peephole2
	       Dump after the peephole pass.

	   -fdump-rtl-postreload
	       Dump after post-reload optimizations.

	   -fdump-rtl-pro_and_epilogue
	       Dump after generating the function prologues and epilogues.

	   -fdump-rtl-regmove
	       Dump after the register move pass.

	   -fdump-rtl-sched1
	   -fdump-rtl-sched2
	       -fdump-rtl-sched1 and -fdump-rtl-sched2 enable dumping after
	       the basic block scheduling passes.

	   -fdump-rtl-see
	       Dump after sign extension elimination.

	   -fdump-rtl-seqabstr
	       Dump after common sequence discovery.

	   -fdump-rtl-shorten
	       Dump after shortening branches.

	   -fdump-rtl-sibling
	       Dump after sibling call optimizations.

	   -fdump-rtl-split1
	   -fdump-rtl-split2
	   -fdump-rtl-split3
	   -fdump-rtl-split4
	   -fdump-rtl-split5
	       -fdump-rtl-split1, -fdump-rtl-split2, -fdump-rtl-split3,
	       -fdump-rtl-split4 and -fdump-rtl-split5 enable dumping after
	       five rounds of instruction splitting.

	   -fdump-rtl-sms
	       Dump after modulo scheduling.  This pass is only run on some
	       architectures.

	   -fdump-rtl-stack
	       Dump after conversion from GCC's "flat register file" registers
	       to the x87's stack-like registers.  This pass is only run on
	       x86 variants.

	   -fdump-rtl-subreg1
	   -fdump-rtl-subreg2
	       -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable dumping after
	       the two subreg expansion passes.

	   -fdump-rtl-unshare
	       Dump after all rtl has been unshared.

	   -fdump-rtl-vartrack
	       Dump after variable tracking.

	   -fdump-rtl-vregs
	       Dump after converting virtual registers to hard registers.

	   -fdump-rtl-web
	       Dump after live range splitting.

	   -fdump-rtl-regclass
	   -fdump-rtl-subregs_of_mode_init
	   -fdump-rtl-subregs_of_mode_finish
	   -fdump-rtl-dfinit
	   -fdump-rtl-dfinish
	       These dumps are defined but always produce empty files.

	   -da
	   -fdump-rtl-all
	       Produce all the dumps listed above.

	   -dA Annotate the assembler output with miscellaneous debugging
	       information.

	   -dD Dump all macro definitions, at the end of preprocessing, in
	       addition to normal output.

	   -dH Produce a core dump whenever an error occurs.

	   -dp Annotate the assembler output with a comment indicating which
	       pattern and alternative is used.	 The length of each
	       instruction is also printed.

	   -dP Dump the RTL in the assembler output as a comment before each
	       instruction.  Also turns on -dp annotation.

	   -dx Just generate RTL for a function instead of compiling it.
	       Usually used with -fdump-rtl-expand.

       -fdump-noaddr
	   When doing debugging dumps, suppress address output.	 This makes it
	   more feasible to use diff on debugging dumps for compiler
	   invocations with different compiler binaries and/or different text
	   / bss / data / heap / stack / dso start locations.

       -fdump-unnumbered
	   When doing debugging dumps, suppress instruction numbers and
	   address output.  This makes it more feasible to use diff on
	   debugging dumps for compiler invocations with different options, in
	   particular with and without -g.

       -fdump-unnumbered-links
	   When doing debugging dumps (see -d option above), suppress
	   instruction numbers for the links to the previous and next
	   instructions in a sequence.

       -fdump-translation-unit (C++ only)
       -fdump-translation-unit-options (C++ only)
	   Dump a representation of the tree structure for the entire
	   translation unit to a file.	The file name is made by appending .tu
	   to the source file name, and the file is created in the same
	   directory as the output file.  If the -options form is used,
	   options controls the details of the dump as described for the
	   -fdump-tree options.

       -fdump-class-hierarchy (C++ only)
       -fdump-class-hierarchy-options (C++ only)
	   Dump a representation of each class's hierarchy and virtual
	   function table layout to a file.  The file name is made by
	   appending .class to the source file name, and the file is created
	   in the same directory as the output file.  If the -options form is
	   used, options controls the details of the dump as described for the
	   -fdump-tree options.

       -fdump-ipa-switch
	   Control the dumping at various stages of inter-procedural analysis
	   language tree to a file.  The file name is generated by appending a
	   switch specific suffix to the source file name, and the file is
	   created in the same directory as the output file.  The following
	   dumps are possible:

	   all Enables all inter-procedural analysis dumps.

	   cgraph
	       Dumps information about call-graph optimization, unused
	       function removal, and inlining decisions.

	   inline
	       Dump after function inlining.

       -fdump-passes
	   Dump the list of optimization passes that are turned on and off by
	   the current command-line options.

       -fdump-statistics-option
	   Enable and control dumping of pass statistics in a separate file.
	   The file name is generated by appending a suffix ending in
	   .statistics to the source file name, and the file is created in the
	   same directory as the output file.  If the -option form is used,
	   -stats causes counters to be summed over the whole compilation unit
	   while -details dumps every event as the passes generate them.  The
	   default with no option is to sum counters for each function
	   compiled.

       -fdump-tree-switch
       -fdump-tree-switch-options
       -fdump-tree-switch-options=filename
	   Control the dumping at various stages of processing the
	   intermediate language tree to a file.  The file name is generated
	   by appending a switch-specific suffix to the source file name, and
	   the file is created in the same directory as the output file. In
	   case of =filename option, the dump is output on the given file
	   instead of the auto named dump files.  If the -options form is
	   used, options is a list of - separated options which control the
	   details of the dump.	 Not all options are applicable to all dumps;
	   those that are not meaningful are ignored.  The following options
	   are available

	   address
	       Print the address of each node.	Usually this is not meaningful
	       as it changes according to the environment and source file.
	       Its primary use is for tying up a dump file with a debug
	       environment.

	   asmname
	       If "DECL_ASSEMBLER_NAME" has been set for a given decl, use
	       that in the dump instead of "DECL_NAME".	 Its primary use is
	       ease of use working backward from mangled names in the assembly
	       file.

	   slim
	       When dumping front-end intermediate representations, inhibit
	       dumping of members of a scope or body of a function merely
	       because that scope has been reached.  Only dump such items when
	       they are directly reachable by some other path.

	       When dumping pretty-printed trees, this option inhibits dumping
	       the bodies of control structures.

	       When dumping RTL, print the RTL in slim (condensed) form
	       instead of the default LISP-like representation.

	   raw Print a raw representation of the tree.	By default, trees are
	       pretty-printed into a C-like representation.

	   details
	       Enable more detailed dumps (not honored by every dump option).
	       Also include information from the optimization passes.

	   stats
	       Enable dumping various statistics about the pass (not honored
	       by every dump option).

	   blocks
	       Enable showing basic block boundaries (disabled in raw dumps).

	   graph
	       For each of the other indicated dump files (-fdump-rtl-pass),
	       dump a representation of the control flow graph suitable for
	       viewing with GraphViz to file.passid.pass.dot.  Each function
	       in the file is pretty-printed as a subgraph, so that GraphViz
	       can render them all in a single plot.

	       This option currently only works for RTL dumps, and the RTL is
	       always dumped in slim form.

	   vops
	       Enable showing virtual operands for every statement.

	   lineno
	       Enable showing line numbers for statements.

	   uid Enable showing the unique ID ("DECL_UID") for each variable.

	   verbose
	       Enable showing the tree dump for each statement.

	   eh  Enable showing the EH region number holding each statement.

	   scev
	       Enable showing scalar evolution analysis details.

	   optimized
	       Enable showing optimization information (only available in
	       certain passes).

	   missed
	       Enable showing missed optimization information (only available
	       in certain passes).

	   notes
	       Enable other detailed optimization information (only available
	       in certain passes).

	   =filename
	       Instead of an auto named dump file, output into the given file
	       name. The file names stdout and stderr are treated specially
	       and are considered already open standard streams. For example,

		       gcc -O2 -ftree-vectorize -fdump-tree-vect-blocks=foo.dump
			    -fdump-tree-pre=stderr file.c

	       outputs vectorizer dump into foo.dump, while the PRE dump is
	       output on to stderr. If two conflicting dump filenames are
	       given for the same pass, then the latter option overrides the
	       earlier one.

	   all Turn on all options, except raw, slim, verbose and lineno.

	   optall
	       Turn on all optimization options, i.e., optimized, missed, and
	       note.

	   The following tree dumps are possible:

	   original
	       Dump before any tree based optimization, to file.original.

	   optimized
	       Dump after all tree based optimization, to file.optimized.

	   gimple
	       Dump each function before and after the gimplification pass to
	       a file.	The file name is made by appending .gimple to the
	       source file name.

	   cfg Dump the control flow graph of each function to a file.	The
	       file name is made by appending .cfg to the source file name.

	   ch  Dump each function after copying loop headers.  The file name
	       is made by appending .ch to the source file name.

	   ssa Dump SSA related information to a file.	The file name is made
	       by appending .ssa to the source file name.

	   alias
	       Dump aliasing information for each function.  The file name is
	       made by appending .alias to the source file name.

	   ccp Dump each function after CCP.  The file name is made by
	       appending .ccp to the source file name.

	   storeccp
	       Dump each function after STORE-CCP.  The file name is made by
	       appending .storeccp to the source file name.

	   pre Dump trees after partial redundancy elimination.	 The file name
	       is made by appending .pre to the source file name.

	   fre Dump trees after full redundancy elimination.  The file name is
	       made by appending .fre to the source file name.

	   copyprop
	       Dump trees after copy propagation.  The file name is made by
	       appending .copyprop to the source file name.

	   store_copyprop
	       Dump trees after store copy-propagation.	 The file name is made
	       by appending .store_copyprop to the source file name.

	   dce Dump each function after dead code elimination.	The file name
	       is made by appending .dce to the source file name.

	   mudflap
	       Dump each function after adding mudflap instrumentation.	 The
	       file name is made by appending .mudflap to the source file
	       name.

	   sra Dump each function after performing scalar replacement of
	       aggregates.  The file name is made by appending .sra to the
	       source file name.

	   sink
	       Dump each function after performing code sinking.  The file
	       name is made by appending .sink to the source file name.

	   dom Dump each function after applying dominator tree optimizations.
	       The file name is made by appending .dom to the source file
	       name.

	   dse Dump each function after applying dead store elimination.  The
	       file name is made by appending .dse to the source file name.

	   phiopt
	       Dump each function after optimizing PHI nodes into straightline
	       code.  The file name is made by appending .phiopt to the source
	       file name.

	   forwprop
	       Dump each function after forward propagating single use
	       variables.  The file name is made by appending .forwprop to the
	       source file name.

	   copyrename
	       Dump each function after applying the copy rename optimization.
	       The file name is made by appending .copyrename to the source
	       file name.

	   nrv Dump each function after applying the named return value
	       optimization on generic trees.  The file name is made by
	       appending .nrv to the source file name.

	   vect
	       Dump each function after applying vectorization of loops.  The
	       file name is made by appending .vect to the source file name.

	   slp Dump each function after applying vectorization of basic
	       blocks.	The file name is made by appending .slp to the source
	       file name.

	   vrp Dump each function after Value Range Propagation (VRP).	The
	       file name is made by appending .vrp to the source file name.

	   all Enable all the available tree dumps with the flags provided in
	       this option.

       -fopt-info
       -fopt-info-options
       -fopt-info-options=filename
	   Controls optimization dumps from various optimization passes. If
	   the -options form is used, options is a list of - separated options
	   to select the dump details and optimizations.  If options is not
	   specified, it defaults to all for details and optall for
	   optimization groups. If the filename is not specified, it defaults
	   to stderr. Note that the output filename will be overwritten in
	   case of multiple translation units. If a combined output from
	   multiple translation units is desired, stderr should be used
	   instead.

	   The options can be divided into two groups, 1) options describing
	   the verbosity of the dump, and 2) options describing which
	   optimizations should be included. The options from both the groups
	   can be freely mixed as they are non-overlapping. However, in case
	   of any conflicts, the latter options override the earlier options
	   on the command line. Though multiple -fopt-info options are
	   accepted, only one of them can have =filename. If other filenames
	   are provided then all but the first one are ignored.

	   The dump verbosity has the following options

	   optimized
	       Print information when an optimization is successfully applied.
	       It is up to a pass to decide which information is relevant. For
	       example, the vectorizer passes print the source location of
	       loops which got successfully vectorized.

	   missed
	       Print information about missed optimizations. Individual passes
	       control which information to include in the output. For
	       example,

		       gcc -O2 -ftree-vectorize -fopt-info-vec-missed

	       will print information about missed optimization opportunities
	       from vectorization passes on stderr.

	   note
	       Print verbose information about optimizations, such as certain
	       transformations, more detailed messages about decisions etc.

	   all Print detailed optimization information. This includes
	       optimized, missed, and note.

	   The second set of options describes a group of optimizations and
	   may include one or more of the following.

	   ipa Enable dumps from all interprocedural optimizations.

	   loop
	       Enable dumps from all loop optimizations.

	   inline
	       Enable dumps from all inlining optimizations.

	   vec Enable dumps from all vectorization optimizations.

	   For example,

		   gcc -O3 -fopt-info-missed=missed.all

	   outputs missed optimization report from all the passes into
	   missed.all.

	   As another example,

		   gcc -O3 -fopt-info-inline-optimized-missed=inline.txt

	   will output information about missed optimizations as well as
	   optimized locations from all the inlining passes into inline.txt.

	   If the filename is provided, then the dumps from all the applicable
	   optimizations are concatenated into the filename.  Otherwise the
	   dump is output onto stderr. If options is omitted, it defaults to
	   all-optall, which means dump all available optimization info from
	   all the passes. In the following example, all optimization info is
	   output on to stderr.

		   gcc -O3 -fopt-info

	   Note that -fopt-info-vec-missed behaves the same as
	   -fopt-info-missed-vec.

	   As another example, consider

		   gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt

	   Here the two output filenames vec.miss and loop.opt are in conflict
	   since only one output file is allowed. In this case, only the first
	   option takes effect and the subsequent options are ignored. Thus
	   only the vec.miss is produced which cotaints dumps from the
	   vectorizer about missed opportunities.

       -ftree-vectorizer-verbose=n
	   This option is deprecated and is implemented in terms of
	   -fopt-info. Please use -fopt-info-kind form instead, where kind is
	   one of the valid opt-info options. It prints additional
	   optimization information.  For n=0 no diagnostic information is
	   reported.  If n=1 the vectorizer reports each loop that got
	   vectorized, and the total number of loops that got vectorized.  If
	   n=2 the vectorizer reports locations which could not be vectorized
	   and the reasons for those. For any higher verbosity levels all the
	   analysis and transformation information from the vectorizer is
	   reported.

	   Note that the information output by -ftree-vectorizer-verbose
	   option is sent to stderr. If the equivalent form
	   -fopt-info-options=filename is used then the output is sent into
	   filename instead.

       -frandom-seed=string
	   This option provides a seed that GCC uses in place of random
	   numbers in generating certain symbol names that have to be
	   different in every compiled file.  It is also used to place unique
	   stamps in coverage data files and the object files that produce
	   them.  You can use the -frandom-seed option to produce reproducibly
	   identical object files.

	   The string should be different for every file you compile.

       -fsched-verbose=n
	   On targets that use instruction scheduling, this option controls
	   the amount of debugging output the scheduler prints.	 This
	   information is written to standard error, unless -fdump-rtl-sched1
	   or -fdump-rtl-sched2 is specified, in which case it is output to
	   the usual dump listing file, .sched1 or .sched2 respectively.
	   However for n greater than nine, the output is always printed to
	   standard error.

	   For n greater than zero, -fsched-verbose outputs the same
	   information as -fdump-rtl-sched1 and -fdump-rtl-sched2.  For n
	   greater than one, it also output basic block probabilities,
	   detailed ready list information and unit/insn info.	For n greater
	   than two, it includes RTL at abort point, control-flow and regions
	   info.  And for n over four, -fsched-verbose also includes
	   dependence info.

       -save-temps
       -save-temps=cwd
	   Store the usual "temporary" intermediate files permanently; place
	   them in the current directory and name them based on the source
	   file.  Thus, compiling foo.c with -c -save-temps produces files
	   foo.i and foo.s, as well as foo.o.  This creates a preprocessed
	   foo.i output file even though the compiler now normally uses an
	   integrated preprocessor.

	   When used in combination with the -x command-line option,
	   -save-temps is sensible enough to avoid over writing an input
	   source file with the same extension as an intermediate file.	 The
	   corresponding intermediate file may be obtained by renaming the
	   source file before using -save-temps.

	   If you invoke GCC in parallel, compiling several different source
	   files that share a common base name in different subdirectories or
	   the same source file compiled for multiple output destinations, it
	   is likely that the different parallel compilers will interfere with
	   each other, and overwrite the temporary files.  For instance:

		   gcc -save-temps -o outdir1/foo.o indir1/foo.c&
		   gcc -save-temps -o outdir2/foo.o indir2/foo.c&

	   may result in foo.i and foo.o being written to simultaneously by
	   both compilers.

       -save-temps=obj
	   Store the usual "temporary" intermediate files permanently.	If the
	   -o option is used, the temporary files are based on the object
	   file.  If the -o option is not used, the -save-temps=obj switch
	   behaves like -save-temps.

	   For example:

		   gcc -save-temps=obj -c foo.c
		   gcc -save-temps=obj -c bar.c -o dir/xbar.o
		   gcc -save-temps=obj foobar.c -o dir2/yfoobar

	   creates foo.i, foo.s, dir/xbar.i, dir/xbar.s, dir2/yfoobar.i,
	   dir2/yfoobar.s, and dir2/yfoobar.o.

       -time[=file]
	   Report the CPU time taken by each subprocess in the compilation
	   sequence.  For C source files, this is the compiler proper and
	   assembler (plus the linker if linking is done).

	   Without the specification of an output file, the output looks like
	   this:

		   # cc1 0.12 0.01
		   # as 0.00 0.01

	   The first number on each line is the "user time", that is time
	   spent executing the program itself.	The second number is "system
	   time", time spent executing operating system routines on behalf of
	   the program.	 Both numbers are in seconds.

	   With the specification of an output file, the output is appended to
	   the named file, and it looks like this:

		   0.12 0.01 cc1 <options>
		   0.00 0.01 as <options>

	   The "user time" and the "system time" are moved before the program
	   name, and the options passed to the program are displayed, so that
	   one can later tell what file was being compiled, and with which
	   options.

       -fvar-tracking
	   Run variable tracking pass.	It computes where variables are stored
	   at each position in code.  Better debugging information is then
	   generated (if the debugging information format supports this
	   information).

	   It is enabled by default when compiling with optimization (-Os, -O,
	   -O2, ...), debugging information (-g) and the debug info format
	   supports it.

       -fvar-tracking-assignments
	   Annotate assignments to user variables early in the compilation and
	   attempt to carry the annotations over throughout the compilation
	   all the way to the end, in an attempt to improve debug information
	   while optimizing.  Use of -gdwarf-4 is recommended along with it.

	   It can be enabled even if var-tracking is disabled, in which case
	   annotations are created and maintained, but discarded at the end.

       -fvar-tracking-assignments-toggle
	   Toggle -fvar-tracking-assignments, in the same way that -gtoggle
	   toggles -g.

       -print-file-name=library
	   Print the full absolute name of the library file library that would
	   be used when linking---and don't do anything else.  With this
	   option, GCC does not compile or link anything; it just prints the
	   file name.

       -print-multi-directory
	   Print the directory name corresponding to the multilib selected by
	   any other switches present in the command line.  This directory is
	   supposed to exist in GCC_EXEC_PREFIX.

       -print-multi-lib
	   Print the mapping from multilib directory names to compiler
	   switches that enable them.  The directory name is separated from
	   the switches by ;, and each switch starts with an @ instead of the
	   -, without spaces between multiple switches.	 This is supposed to
	   ease shell processing.

       -print-multi-os-directory
	   Print the path to OS libraries for the selected multilib, relative
	   to some lib subdirectory.  If OS libraries are present in the lib
	   subdirectory and no multilibs are used, this is usually just ., if
	   OS libraries are present in libsuffix sibling directories this
	   prints e.g. ../lib64, ../lib or ../lib32, or if OS libraries are
	   present in lib/subdir subdirectories it prints e.g. amd64, sparcv9
	   or ev6.

       -print-multiarch
	   Print the path to OS libraries for the selected multiarch, relative
	   to some lib subdirectory.

       -print-prog-name=program
	   Like -print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
	   Same as -print-file-name=libgcc.a.

	   This is useful when you use -nostdlib or -nodefaultlibs but you do
	   want to link with libgcc.a.	You can do:

		   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
	   Print the name of the configured installation directory and a list
	   of program and library directories gcc searches---and don't do
	   anything else.

	   This is useful when gcc prints the error message installation
	   problem, cannot exec cpp0: No such file or directory.  To resolve
	   this you either need to put cpp0 and the other compiler components
	   where gcc expects to find them, or you can set the environment
	   variable GCC_EXEC_PREFIX to the directory where you installed them.
	   Don't forget the trailing /.

       -print-sysroot
	   Print the target sysroot directory that is used during compilation.
	   This is the target sysroot specified either at configure time or
	   using the --sysroot option, possibly with an extra suffix that
	   depends on compilation options.  If no target sysroot is specified,
	   the option prints nothing.

       -print-sysroot-headers-suffix
	   Print the suffix added to the target sysroot when searching for
	   headers, or give an error if the compiler is not configured with
	   such a suffix---and don't do anything else.

       -dumpmachine
	   Print the compiler's target machine (for example,
	   i686-pc-linux-gnu)---and don't do anything else.

       -dumpversion
	   Print the compiler version (for example, 3.0)---and don't do
	   anything else.

       -dumpspecs
	   Print the compiler's built-in specs---and don't do anything else.
	   (This is used when GCC itself is being built.)

       -fno-eliminate-unused-debug-types
	   Normally, when producing DWARF 2 output, GCC avoids producing debug
	   symbol output for types that are nowhere used in the source file
	   being compiled.  Sometimes it is useful to have GCC emit debugging
	   information for all types declared in a compilation unit,
	   regardless of whether or not they are actually used in that
	   compilation unit, for example if, in the debugger, you want to cast
	   a value to a type that is not actually used in your program (but is
	   declared).  More often, however, this results in a significant
	   amount of wasted space.

   Options That Control Optimization
       These options control various sorts of optimizations.

       Without any optimization option, the compiler's goal is to reduce the
       cost of compilation and to make debugging produce the expected results.
       Statements are independent: if you stop the program with a breakpoint
       between statements, you can then assign a new value to any variable or
       change the program counter to any other statement in the function and
       get exactly the results you expect from the source code.

       Turning on optimization flags makes the compiler attempt to improve the
       performance and/or code size at the expense of compilation time and
       possibly the ability to debug the program.

       The compiler performs optimization based on the knowledge it has of the
       program.	 Compiling multiple files at once to a single output file mode
       allows the compiler to use information gained from all of the files
       when compiling each of them.

       Not all optimizations are controlled directly by a flag.	 Only
       optimizations that have a flag are listed in this section.

       Most optimizations are only enabled if an -O level is set on the
       command line.  Otherwise they are disabled, even if individual
       optimization flags are specified.

       Depending on the target and how GCC was configured, a slightly
       different set of optimizations may be enabled at each -O level than
       those listed here.  You can invoke GCC with -Q --help=optimizers to
       find out the exact set of optimizations that are enabled at each level.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time, and a
	   lot more memory for a large function.

	   With -O, the compiler tries to reduce code size and execution time,
	   without performing any optimizations that take a great deal of
	   compilation time.

	   -O turns on the following optimization flags:

	   -fauto-inc-dec -fcompare-elim -fcprop-registers -fdce -fdefer-pop
	   -fdelayed-branch -fdse -fguess-branch-probability -fif-conversion2
	   -fif-conversion -fipa-pure-const -fipa-profile -fipa-reference
	   -fmerge-constants -fsplit-wide-types -ftree-bit-ccp
	   -ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-copyrename
	   -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop
	   -ftree-fre -ftree-phiprop -ftree-slsr -ftree-sra -ftree-pta
	   -ftree-ter -funit-at-a-time

	   -O also turns on -fomit-frame-pointer on machines where doing so
	   does not interfere with debugging.

       -O2 Optimize even more.	GCC performs nearly all supported
	   optimizations that do not involve a space-speed tradeoff.  As
	   compared to -O, this option increases both compilation time and the
	   performance of the generated code.

	   -O2 turns on all optimization flags specified by -O.	 It also turns
	   on the following optimization flags: -fthread-jumps
	   -falign-functions  -falign-jumps -falign-loops  -falign-labels
	   -fcaller-saves -fcrossjumping -fcse-follow-jumps  -fcse-skip-blocks
	   -fdelete-null-pointer-checks -fdevirtualize
	   -fexpensive-optimizations -fgcse  -fgcse-lm -fhoist-adjacent-loads
	   -finline-small-functions -findirect-inlining -fipa-sra
	   -foptimize-sibling-calls -fpartial-inlining -fpeephole2 -fregmove
	   -freorder-blocks  -freorder-functions -frerun-cse-after-loop
	   -fsched-interblock  -fsched-spec -fschedule-insns
	   -fschedule-insns2 -fstrict-aliasing -fstrict-overflow
	   -ftree-switch-conversion -ftree-tail-merge -ftree-pre -ftree-vrp

	   Please note the warning under -fgcse about invoking -O2 on programs
	   that use computed gotos.

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2
	   and also turns on the -finline-functions, -funswitch-loops,
	   -fpredictive-commoning, -fgcse-after-reload, -ftree-vectorize,
	   -fvect-cost-model, -ftree-partial-pre and -fipa-cp-clone options.

       -O0 Reduce compilation time and make debugging produce the expected
	   results.  This is the default.

       -Os Optimize for size.  -Os enables all -O2 optimizations that do not
	   typically increase code size.  It also performs further
	   optimizations designed to reduce code size.

	   -Os disables the following optimization flags: -falign-functions
	   -falign-jumps  -falign-loops -falign-labels	-freorder-blocks
	   -freorder-blocks-and-partition -fprefetch-loop-arrays
	   -ftree-vect-loop-version

       -Ofast
	   Disregard strict standards compliance.  -Ofast enables all -O3
	   optimizations.  It also enables optimizations that are not valid
	   for all standard-compliant programs.	 It turns on -ffast-math and
	   the Fortran-specific -fno-protect-parens and -fstack-arrays.

       -Og Optimize debugging experience.  -Og enables optimizations that do
	   not interfere with debugging. It should be the optimization level
	   of choice for the standard edit-compile-debug cycle, offering a
	   reasonable level of optimization while maintaining fast compilation
	   and a good debugging experience.

	   If you use multiple -O options, with or without level numbers, the
	   last such option is the one that is effective.

       Options of the form -fflag specify machine-independent flags.  Most
       flags have both positive and negative forms; the negative form of -ffoo
       is -fno-foo.  In the table below, only one of the forms is listed---the
       one you typically use.  You can figure out the other form by either
       removing no- or adding it.

       The following options control specific optimizations.  They are either
       activated by -O options or are related to ones that are.	 You can use
       the following flags in the rare cases when "fine-tuning" of
       optimizations to be performed is desired.

       -fno-default-inline
	   Do not make member functions inline by default merely because they
	   are defined inside the class scope (C++ only).  Otherwise, when you
	   specify -O, member functions defined inside class scope are
	   compiled inline by default; i.e., you don't need to add inline in
	   front of the member function name.

       -fno-defer-pop
	   Always pop the arguments to each function call as soon as that
	   function returns.  For machines that must pop arguments after a
	   function call, the compiler normally lets arguments accumulate on
	   the stack for several function calls and pops them all at once.

	   Disabled at levels -O, -O2, -O3, -Os.

       -fforward-propagate
	   Perform a forward propagation pass on RTL.  The pass tries to
	   combine two instructions and checks if the result can be
	   simplified.	If loop unrolling is active, two passes are performed
	   and the second is scheduled after loop unrolling.

	   This option is enabled by default at optimization levels -O, -O2,
	   -O3, -Os.

       -ffp-contract=style
	   -ffp-contract=off disables floating-point expression contraction.
	   -ffp-contract=fast enables floating-point expression contraction
	   such as forming of fused multiply-add operations if the target has
	   native support for them.  -ffp-contract=on enables floating-point
	   expression contraction if allowed by the language standard.	This
	   is currently not implemented and treated equal to
	   -ffp-contract=off.

	   The default is -ffp-contract=fast.

       -fomit-frame-pointer
	   Don't keep the frame pointer in a register for functions that don't
	   need one.  This avoids the instructions to save, set up and restore
	   frame pointers; it also makes an extra register available in many
	   functions.  It also makes debugging impossible on some machines.

	   On some machines, such as the VAX, this flag has no effect, because
	   the standard calling sequence automatically handles the frame
	   pointer and nothing is saved by pretending it doesn't exist.	 The
	   machine-description macro "FRAME_POINTER_REQUIRED" controls whether
	   a target machine supports this flag.

	   Starting with GCC version 4.6, the default setting (when not
	   optimizing for size) for 32-bit GNU/Linux x86 and 32-bit Darwin x86
	   targets has been changed to -fomit-frame-pointer.  The default can
	   be reverted to -fno-omit-frame-pointer by configuring GCC with the
	   --enable-frame-pointer configure option.

	   Enabled at levels -O, -O2, -O3, -Os.

       -foptimize-sibling-calls
	   Optimize sibling and tail recursive calls.

	   Enabled at levels -O2, -O3, -Os.

       -fno-inline
	   Do not expand any functions inline apart from those marked with the
	   "always_inline" attribute.  This is the default when not
	   optimizing.

	   Single functions can be exempted from inlining by marking them with
	   the "noinline" attribute.

       -finline-small-functions
	   Integrate functions into their callers when their body is smaller
	   than expected function call code (so overall size of program gets
	   smaller).  The compiler heuristically decides which functions are
	   simple enough to be worth integrating in this way.  This inlining
	   applies to all functions, even those not declared inline.

	   Enabled at level -O2.

       -findirect-inlining
	   Inline also indirect calls that are discovered to be known at
	   compile time thanks to previous inlining.  This option has any
	   effect only when inlining itself is turned on by the
	   -finline-functions or -finline-small-functions options.

	   Enabled at level -O2.

       -finline-functions
	   Consider all functions for inlining, even if they are not declared
	   inline.  The compiler heuristically decides which functions are
	   worth integrating in this way.

	   If all calls to a given function are integrated, and the function
	   is declared "static", then the function is normally not output as
	   assembler code in its own right.

	   Enabled at level -O3.

       -finline-functions-called-once
	   Consider all "static" functions called once for inlining into their
	   caller even if they are not marked "inline".	 If a call to a given
	   function is integrated, then the function is not output as
	   assembler code in its own right.

	   Enabled at levels -O1, -O2, -O3 and -Os.

       -fearly-inlining
	   Inline functions marked by "always_inline" and functions whose body
	   seems smaller than the function call overhead early before doing
	   -fprofile-generate instrumentation and real inlining pass.  Doing
	   so makes profiling significantly cheaper and usually inlining
	   faster on programs having large chains of nested wrapper functions.

	   Enabled by default.

       -fipa-sra
	   Perform interprocedural scalar replacement of aggregates, removal
	   of unused parameters and replacement of parameters passed by
	   reference by parameters passed by value.

	   Enabled at levels -O2, -O3 and -Os.

       -finline-limit=n
	   By default, GCC limits the size of functions that can be inlined.
	   This flag allows coarse control of this limit.  n is the size of
	   functions that can be inlined in number of pseudo instructions.

	   Inlining is actually controlled by a number of parameters, which
	   may be specified individually by using --param name=value.  The
	   -finline-limit=n option sets some of these parameters as follows:

	   max-inline-insns-single
	       is set to n/2.

	   max-inline-insns-auto
	       is set to n/2.

	   See below for a documentation of the individual parameters
	   controlling inlining and for the defaults of these parameters.

	   Note: there may be no value to -finline-limit that results in
	   default behavior.

	   Note: pseudo instruction represents, in this particular context, an
	   abstract measurement of function's size.  In no way does it
	   represent a count of assembly instructions and as such its exact
	   meaning might change from one release to an another.

       -fno-keep-inline-dllexport
	   This is a more fine-grained version of -fkeep-inline-functions,
	   which applies only to functions that are declared using the
	   "dllexport" attribute or declspec

       -fkeep-inline-functions
	   In C, emit "static" functions that are declared "inline" into the
	   object file, even if the function has been inlined into all of its
	   callers.  This switch does not affect functions using the "extern
	   inline" extension in GNU C90.  In C++, emit any and all inline
	   functions into the object file.

       -fkeep-static-consts
	   Emit variables declared "static const" when optimization isn't
	   turned on, even if the variables aren't referenced.

	   GCC enables this option by default.	If you want to force the
	   compiler to check if a variable is referenced, regardless of
	   whether or not optimization is turned on, use the
	   -fno-keep-static-consts option.

       -fmerge-constants
	   Attempt to merge identical constants (string constants and
	   floating-point constants) across compilation units.

	   This option is the default for optimized compilation if the
	   assembler and linker support it.  Use -fno-merge-constants to
	   inhibit this behavior.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fmerge-all-constants
	   Attempt to merge identical constants and identical variables.

	   This option implies -fmerge-constants.  In addition to
	   -fmerge-constants this considers e.g. even constant initialized
	   arrays or initialized constant variables with integral or floating-
	   point types.	 Languages like C or C++ require each variable,
	   including multiple instances of the same variable in recursive
	   calls, to have distinct locations, so using this option results in
	   non-conforming behavior.

       -fmodulo-sched
	   Perform swing modulo scheduling immediately before the first
	   scheduling pass.  This pass looks at innermost loops and reorders
	   their instructions by overlapping different iterations.

       -fmodulo-sched-allow-regmoves
	   Perform more aggressive SMS-based modulo scheduling with register
	   moves allowed.  By setting this flag certain anti-dependences edges
	   are deleted, which triggers the generation of reg-moves based on
	   the life-range analysis.  This option is effective only with
	   -fmodulo-sched enabled.

       -fno-branch-count-reg
	   Do not use "decrement and branch" instructions on a count register,
	   but instead generate a sequence of instructions that decrement a
	   register, compare it against zero, then branch based upon the
	   result.  This option is only meaningful on architectures that
	   support such instructions, which include x86, PowerPC, IA-64 and
	   S/390.

	   The default is -fbranch-count-reg.

       -fno-function-cse
	   Do not put function addresses in registers; make each instruction
	   that calls a constant function contain the function's address
	   explicitly.

	   This option results in less efficient code, but some strange hacks
	   that alter the assembler output may be confused by the
	   optimizations performed when this option is not used.

	   The default is -ffunction-cse

       -fno-zero-initialized-in-bss
	   If the target supports a BSS section, GCC by default puts variables
	   that are initialized to zero into BSS.  This can save space in the
	   resulting code.

	   This option turns off this behavior because some programs
	   explicitly rely on variables going to the data section---e.g., so
	   that the resulting executable can find the beginning of that
	   section and/or make assumptions based on that.

	   The default is -fzero-initialized-in-bss.

       -fmudflap -fmudflapth -fmudflapir
	   For front-ends that support it (C and C++), instrument all risky
	   pointer/array dereferencing operations, some standard library
	   string/heap functions, and some other associated constructs with
	   range/validity tests.  Modules so instrumented should be immune to
	   buffer overflows, invalid heap use, and some other classes of C/C++
	   programming errors.	The instrumentation relies on a separate
	   runtime library (libmudflap), which is linked into a program if
	   -fmudflap is given at link time.  Run-time behavior of the
	   instrumented program is controlled by the MUDFLAP_OPTIONS
	   environment variable.  See "env MUDFLAP_OPTIONS=-help a.out" for
	   its options.

	   Use -fmudflapth instead of -fmudflap to compile and to link if your
	   program is multi-threaded.  Use -fmudflapir, in addition to
	   -fmudflap or -fmudflapth, if instrumentation should ignore pointer
	   reads.  This produces less instrumentation (and therefore faster
	   execution) and still provides some protection against outright
	   memory corrupting writes, but allows erroneously read data to
	   propagate within a program.

       -fthread-jumps
	   Perform optimizations that check to see if a jump branches to a
	   location where another comparison subsumed by the first is found.
	   If so, the first branch is redirected to either the destination of
	   the second branch or a point immediately following it, depending on
	   whether the condition is known to be true or false.

	   Enabled at levels -O2, -O3, -Os.

       -fsplit-wide-types
	   When using a type that occupies multiple registers, such as "long
	   long" on a 32-bit system, split the registers apart and allocate
	   them independently.	This normally generates better code for those
	   types, but may make debugging more difficult.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fcse-follow-jumps
	   In common subexpression elimination (CSE), scan through jump
	   instructions when the target of the jump is not reached by any
	   other path.	For example, when CSE encounters an "if" statement
	   with an "else" clause, CSE follows the jump when the condition
	   tested is false.

	   Enabled at levels -O2, -O3, -Os.

       -fcse-skip-blocks
	   This is similar to -fcse-follow-jumps, but causes CSE to follow
	   jumps that conditionally skip over blocks.  When CSE encounters a
	   simple "if" statement with no else clause, -fcse-skip-blocks causes
	   CSE to follow the jump around the body of the "if".

	   Enabled at levels -O2, -O3, -Os.

       -frerun-cse-after-loop
	   Re-run common subexpression elimination after loop optimizations
	   are performed.

	   Enabled at levels -O2, -O3, -Os.

       -fgcse
	   Perform a global common subexpression elimination pass.  This pass
	   also performs global constant and copy propagation.

	   Note: When compiling a program using computed gotos, a GCC
	   extension, you may get better run-time performance if you disable
	   the global common subexpression elimination pass by adding
	   -fno-gcse to the command line.

	   Enabled at levels -O2, -O3, -Os.

       -fgcse-lm
	   When -fgcse-lm is enabled, global common subexpression elimination
	   attempts to move loads that are only killed by stores into
	   themselves.	This allows a loop containing a load/store sequence to
	   be changed to a load outside the loop, and a copy/store within the
	   loop.

	   Enabled by default when -fgcse is enabled.

       -fgcse-sm
	   When -fgcse-sm is enabled, a store motion pass is run after global
	   common subexpression elimination.  This pass attempts to move
	   stores out of loops.	 When used in conjunction with -fgcse-lm,
	   loops containing a load/store sequence can be changed to a load
	   before the loop and a store after the loop.

	   Not enabled at any optimization level.

       -fgcse-las
	   When -fgcse-las is enabled, the global common subexpression
	   elimination pass eliminates redundant loads that come after stores
	   to the same memory location (both partial and full redundancies).

	   Not enabled at any optimization level.

       -fgcse-after-reload
	   When -fgcse-after-reload is enabled, a redundant load elimination
	   pass is performed after reload.  The purpose of this pass is to
	   clean up redundant spilling.

       -faggressive-loop-optimizations
	   This option tells the loop optimizer to use language constraints to
	   derive bounds for the number of iterations of a loop.  This assumes
	   that loop code does not invoke undefined behavior by for example
	   causing signed integer overflows or out-of-bound array accesses.
	   The bounds for the number of iterations of a loop are used to guide
	   loop unrolling and peeling and loop exit test optimizations.	 This
	   option is enabled by default.

       -funsafe-loop-optimizations
	   This option tells the loop optimizer to assume that loop indices do
	   not overflow, and that loops with nontrivial exit condition are not
	   infinite.  This enables a wider range of loop optimizations even if
	   the loop optimizer itself cannot prove that these assumptions are
	   valid.  If you use -Wunsafe-loop-optimizations, the compiler warns
	   you if it finds this kind of loop.

       -fcrossjumping
	   Perform cross-jumping transformation.  This transformation unifies
	   equivalent code and saves code size.	 The resulting code may or may
	   not perform better than without cross-jumping.

	   Enabled at levels -O2, -O3, -Os.

       -fauto-inc-dec
	   Combine increments or decrements of addresses with memory accesses.
	   This pass is always skipped on architectures that do not have
	   instructions to support this.  Enabled by default at -O and higher
	   on architectures that support this.

       -fdce
	   Perform dead code elimination (DCE) on RTL.	Enabled by default at
	   -O and higher.

       -fdse
	   Perform dead store elimination (DSE) on RTL.	 Enabled by default at
	   -O and higher.

       -fif-conversion
	   Attempt to transform conditional jumps into branch-less
	   equivalents.	 This includes use of conditional moves, min, max, set
	   flags and abs instructions, and some tricks doable by standard
	   arithmetics.	 The use of conditional execution on chips where it is
	   available is controlled by "if-conversion2".

	   Enabled at levels -O, -O2, -O3, -Os.

       -fif-conversion2
	   Use conditional execution (where available) to transform
	   conditional jumps into branch-less equivalents.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fdelete-null-pointer-checks
	   Assume that programs cannot safely dereference null pointers, and
	   that no code or data element resides there.	This enables simple
	   constant folding optimizations at all optimization levels.  In
	   addition, other optimization passes in GCC use this flag to control
	   global dataflow analyses that eliminate useless checks for null
	   pointers; these assume that if a pointer is checked after it has
	   already been dereferenced, it cannot be null.

	   Note however that in some environments this assumption is not true.
	   Use -fno-delete-null-pointer-checks to disable this optimization
	   for programs that depend on that behavior.

	   Some targets, especially embedded ones, disable this option at all
	   levels.  Otherwise it is enabled at all levels: -O0, -O1, -O2, -O3,
	   -Os.	 Passes that use the information are enabled independently at
	   different optimization levels.

       -fdevirtualize
	   Attempt to convert calls to virtual functions to direct calls.
	   This is done both within a procedure and interprocedurally as part
	   of indirect inlining ("-findirect-inlining") and interprocedural
	   constant propagation (-fipa-cp).  Enabled at levels -O2, -O3, -Os.

       -fexpensive-optimizations
	   Perform a number of minor optimizations that are relatively
	   expensive.

	   Enabled at levels -O2, -O3, -Os.

       -free
	   Attempt to remove redundant extension instructions.	This is
	   especially helpful for the x86-64 architecture, which implicitly
	   zero-extends in 64-bit registers after writing to their lower
	   32-bit half.

	   Enabled for x86 at levels -O2, -O3.

       -foptimize-register-move
       -fregmove
	   Attempt to reassign register numbers in move instructions and as
	   operands of other simple instructions in order to maximize the
	   amount of register tying.  This is especially helpful on machines
	   with two-operand instructions.

	   Note -fregmove and -foptimize-register-move are the same
	   optimization.

	   Enabled at levels -O2, -O3, -Os.

       -fira-algorithm=algorithm
	   Use the specified coloring algorithm for the integrated register
	   allocator.  The algorithm argument can be priority, which specifies
	   Chow's priority coloring, or CB, which specifies Chaitin-Briggs
	   coloring.  Chaitin-Briggs coloring is not implemented for all
	   architectures, but for those targets that do support it, it is the
	   default because it generates better code.

       -fira-region=region
	   Use specified regions for the integrated register allocator.	 The
	   region argument should be one of the following:

	   all Use all loops as register allocation regions.  This can give
	       the best results for machines with a small and/or irregular
	       register set.

	   mixed
	       Use all loops except for loops with small register pressure as
	       the regions.  This value usually gives the best results in most
	       cases and for most architectures, and is enabled by default
	       when compiling with optimization for speed (-O, -O2, ...).

	   one Use all functions as a single region.  This typically results
	       in the smallest code size, and is enabled by default for -Os or
	       -O0.

       -fira-hoist-pressure
	   Use IRA to evaluate register pressure in the code hoisting pass for
	   decisions to hoist expressions.  This option usually results in
	   smaller code, but it can slow the compiler down.

	   This option is enabled at level -Os for all targets.

       -fira-loop-pressure
	   Use IRA to evaluate register pressure in loops for decisions to
	   move loop invariants.  This option usually results in generation of
	   faster and smaller code on machines with large register files (>=
	   32 registers), but it can slow the compiler down.

	   This option is enabled at level -O3 for some targets.

       -fno-ira-share-save-slots
	   Disable sharing of stack slots used for saving call-used hard
	   registers living through a call.  Each hard register gets a
	   separate stack slot, and as a result function stack frames are
	   larger.

       -fno-ira-share-spill-slots
	   Disable sharing of stack slots allocated for pseudo-registers.
	   Each pseudo-register that does not get a hard register gets a
	   separate stack slot, and as a result function stack frames are
	   larger.

       -fira-verbose=n
	   Control the verbosity of the dump file for the integrated register
	   allocator.  The default value is 5.	If the value n is greater or
	   equal to 10, the dump output is sent to stderr using the same
	   format as n minus 10.

       -fdelayed-branch
	   If supported for the target machine, attempt to reorder
	   instructions to exploit instruction slots available after delayed
	   branch instructions.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fschedule-insns
	   If supported for the target machine, attempt to reorder
	   instructions to eliminate execution stalls due to required data
	   being unavailable.  This helps machines that have slow floating
	   point or memory load instructions by allowing other instructions to
	   be issued until the result of the load or floating-point
	   instruction is required.

	   Enabled at levels -O2, -O3.

       -fschedule-insns2
	   Similar to -fschedule-insns, but requests an additional pass of
	   instruction scheduling after register allocation has been done.
	   This is especially useful on machines with a relatively small
	   number of registers and where memory load instructions take more
	   than one cycle.

	   Enabled at levels -O2, -O3, -Os.

       -fno-sched-interblock
	   Don't schedule instructions across basic blocks.  This is normally
	   enabled by default when scheduling before register allocation, i.e.
	   with -fschedule-insns or at -O2 or higher.

       -fno-sched-spec
	   Don't allow speculative motion of non-load instructions.  This is
	   normally enabled by default when scheduling before register
	   allocation, i.e.  with -fschedule-insns or at -O2 or higher.

       -fsched-pressure
	   Enable register pressure sensitive insn scheduling before register
	   allocation.	This only makes sense when scheduling before register
	   allocation is enabled, i.e. with -fschedule-insns or at -O2 or
	   higher.  Usage of this option can improve the generated code and
	   decrease its size by preventing register pressure increase above
	   the number of available hard registers and subsequent spills in
	   register allocation.

       -fsched-spec-load
	   Allow speculative motion of some load instructions.	This only
	   makes sense when scheduling before register allocation, i.e. with
	   -fschedule-insns or at -O2 or higher.

       -fsched-spec-load-dangerous
	   Allow speculative motion of more load instructions.	This only
	   makes sense when scheduling before register allocation, i.e. with
	   -fschedule-insns or at -O2 or higher.

       -fsched-stalled-insns
       -fsched-stalled-insns=n
	   Define how many insns (if any) can be moved prematurely from the
	   queue of stalled insns into the ready list during the second
	   scheduling pass.  -fno-sched-stalled-insns means that no insns are
	   moved prematurely, -fsched-stalled-insns=0 means there is no limit
	   on how many queued insns can be moved prematurely.
	   -fsched-stalled-insns without a value is equivalent to
	   -fsched-stalled-insns=1.

       -fsched-stalled-insns-dep
       -fsched-stalled-insns-dep=n
	   Define how many insn groups (cycles) are examined for a dependency
	   on a stalled insn that is a candidate for premature removal from
	   the queue of stalled insns.	This has an effect only during the
	   second scheduling pass, and only if -fsched-stalled-insns is used.
	   -fno-sched-stalled-insns-dep is equivalent to
	   -fsched-stalled-insns-dep=0.	 -fsched-stalled-insns-dep without a
	   value is equivalent to -fsched-stalled-insns-dep=1.

       -fsched2-use-superblocks
	   When scheduling after register allocation, use superblock
	   scheduling.	This allows motion across basic block boundaries,
	   resulting in faster schedules.  This option is experimental, as not
	   all machine descriptions used by GCC model the CPU closely enough
	   to avoid unreliable results from the algorithm.

	   This only makes sense when scheduling after register allocation,
	   i.e. with -fschedule-insns2 or at -O2 or higher.

       -fsched-group-heuristic
	   Enable the group heuristic in the scheduler.	 This heuristic favors
	   the instruction that belongs to a schedule group.  This is enabled
	   by default when scheduling is enabled, i.e. with -fschedule-insns
	   or -fschedule-insns2 or at -O2 or higher.

       -fsched-critical-path-heuristic
	   Enable the critical-path heuristic in the scheduler.	 This
	   heuristic favors instructions on the critical path.	This is
	   enabled by default when scheduling is enabled, i.e. with
	   -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-spec-insn-heuristic
	   Enable the speculative instruction heuristic in the scheduler.
	   This heuristic favors speculative instructions with greater
	   dependency weakness.	 This is enabled by default when scheduling is
	   enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2
	   or higher.

       -fsched-rank-heuristic
	   Enable the rank heuristic in the scheduler.	This heuristic favors
	   the instruction belonging to a basic block with greater size or
	   frequency.  This is enabled by default when scheduling is enabled,
	   i.e.	 with -fschedule-insns or -fschedule-insns2 or at -O2 or
	   higher.

       -fsched-last-insn-heuristic
	   Enable the last-instruction heuristic in the scheduler.  This
	   heuristic favors the instruction that is less dependent on the last
	   instruction scheduled.  This is enabled by default when scheduling
	   is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at
	   -O2 or higher.

       -fsched-dep-count-heuristic
	   Enable the dependent-count heuristic in the scheduler.  This
	   heuristic favors the instruction that has more instructions
	   depending on it.  This is enabled by default when scheduling is
	   enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2
	   or higher.

       -freschedule-modulo-scheduled-loops
	   Modulo scheduling is performed before traditional scheduling.  If a
	   loop is modulo scheduled, later scheduling passes may change its
	   schedule.  Use this option to control that behavior.

       -fselective-scheduling
	   Schedule instructions using selective scheduling algorithm.
	   Selective scheduling runs instead of the first scheduler pass.

       -fselective-scheduling2
	   Schedule instructions using selective scheduling algorithm.
	   Selective scheduling runs instead of the second scheduler pass.

       -fsel-sched-pipelining
	   Enable software pipelining of innermost loops during selective
	   scheduling.	This option has no effect unless one of
	   -fselective-scheduling or -fselective-scheduling2 is turned on.

       -fsel-sched-pipelining-outer-loops
	   When pipelining loops during selective scheduling, also pipeline
	   outer loops.	 This option has no effect unless
	   -fsel-sched-pipelining is turned on.

       -fshrink-wrap
	   Emit function prologues only before parts of the function that need
	   it, rather than at the top of the function.	This flag is enabled
	   by default at -O and higher.

       -fcaller-saves
	   Enable allocation of values to registers that are clobbered by
	   function calls, by emitting extra instructions to save and restore
	   the registers around such calls.  Such allocation is done only when
	   it seems to result in better code.

	   This option is always enabled by default on certain machines,
	   usually those which have no call-preserved registers to use
	   instead.

	   Enabled at levels -O2, -O3, -Os.

       -fcombine-stack-adjustments
	   Tracks stack adjustments (pushes and pops) and stack memory
	   references and then tries to find ways to combine them.

	   Enabled by default at -O1 and higher.

       -fconserve-stack
	   Attempt to minimize stack usage.  The compiler attempts to use less
	   stack space, even if that makes the program slower.	This option
	   implies setting the large-stack-frame parameter to 100 and the
	   large-stack-frame-growth parameter to 400.

       -ftree-reassoc
	   Perform reassociation on trees.  This flag is enabled by default at
	   -O and higher.

       -ftree-pre
	   Perform partial redundancy elimination (PRE) on trees.  This flag
	   is enabled by default at -O2 and -O3.

       -ftree-partial-pre
	   Make partial redundancy elimination (PRE) more aggressive.  This
	   flag is enabled by default at -O3.

       -ftree-forwprop
	   Perform forward propagation on trees.  This flag is enabled by
	   default at -O and higher.

       -ftree-fre
	   Perform full redundancy elimination (FRE) on trees.	The difference
	   between FRE and PRE is that FRE only considers expressions that are
	   computed on all paths leading to the redundant computation.	This
	   analysis is faster than PRE, though it exposes fewer redundancies.
	   This flag is enabled by default at -O and higher.

       -ftree-phiprop
	   Perform hoisting of loads from conditional pointers on trees.  This
	   pass is enabled by default at -O and higher.

       -fhoist-adjacent-loads
	   Speculatively hoist loads from both branches of an if-then-else if
	   the loads are from adjacent locations in the same structure and the
	   target architecture has a conditional move instruction.  This flag
	   is enabled by default at -O2 and higher.

       -ftree-copy-prop
	   Perform copy propagation on trees.  This pass eliminates
	   unnecessary copy operations.	 This flag is enabled by default at -O
	   and higher.

       -fipa-pure-const
	   Discover which functions are pure or constant.  Enabled by default
	   at -O and higher.

       -fipa-reference
	   Discover which static variables do not escape the compilation unit.
	   Enabled by default at -O and higher.

       -fipa-pta
	   Perform interprocedural pointer analysis and interprocedural
	   modification and reference analysis.	 This option can cause
	   excessive memory and compile-time usage on large compilation units.
	   It is not enabled by default at any optimization level.

       -fipa-profile
	   Perform interprocedural profile propagation.	 The functions called
	   only from cold functions are marked as cold. Also functions
	   executed once (such as "cold", "noreturn", static constructors or
	   destructors) are identified. Cold functions and loop less parts of
	   functions executed once are then optimized for size.	 Enabled by
	   default at -O and higher.

       -fipa-cp
	   Perform interprocedural constant propagation.  This optimization
	   analyzes the program to determine when values passed to functions
	   are constants and then optimizes accordingly.  This optimization
	   can substantially increase performance if the application has
	   constants passed to functions.  This flag is enabled by default at
	   -O2, -Os and -O3.

       -fipa-cp-clone
	   Perform function cloning to make interprocedural constant
	   propagation stronger.  When enabled, interprocedural constant
	   propagation performs function cloning when externally visible
	   function can be called with constant arguments.  Because this
	   optimization can create multiple copies of functions, it may
	   significantly increase code size (see --param
	   ipcp-unit-growth=value).  This flag is enabled by default at -O3.

       -ftree-sink
	   Perform forward store motion	 on trees.  This flag is enabled by
	   default at -O and higher.

       -ftree-bit-ccp
	   Perform sparse conditional bit constant propagation on trees and
	   propagate pointer alignment information.  This pass only operates
	   on local scalar variables and is enabled by default at -O and
	   higher.  It requires that -ftree-ccp is enabled.

       -ftree-ccp
	   Perform sparse conditional constant propagation (CCP) on trees.
	   This pass only operates on local scalar variables and is enabled by
	   default at -O and higher.

       -ftree-switch-conversion
	   Perform conversion of simple initializations in a switch to
	   initializations from a scalar array.	 This flag is enabled by
	   default at -O2 and higher.

       -ftree-tail-merge
	   Look for identical code sequences.  When found, replace one with a
	   jump to the other.  This optimization is known as tail merging or
	   cross jumping.  This flag is enabled by default at -O2 and higher.
	   The compilation time in this pass can be limited using max-tail-
	   merge-comparisons parameter and max-tail-merge-iterations
	   parameter.

       -ftree-dce
	   Perform dead code elimination (DCE) on trees.  This flag is enabled
	   by default at -O and higher.

       -ftree-builtin-call-dce
	   Perform conditional dead code elimination (DCE) for calls to built-
	   in functions that may set "errno" but are otherwise side-effect
	   free.  This flag is enabled by default at -O2 and higher if -Os is
	   not also specified.

       -ftree-dominator-opts
	   Perform a variety of simple scalar cleanups (constant/copy
	   propagation, redundancy elimination, range propagation and
	   expression simplification) based on a dominator tree traversal.
	   This also performs jump threading (to reduce jumps to jumps). This
	   flag is enabled by default at -O and higher.

       -ftree-dse
	   Perform dead store elimination (DSE) on trees.  A dead store is a
	   store into a memory location that is later overwritten by another
	   store without any intervening loads.	 In this case the earlier
	   store can be deleted.  This flag is enabled by default at -O and
	   higher.

       -ftree-ch
	   Perform loop header copying on trees.  This is beneficial since it
	   increases effectiveness of code motion optimizations.  It also
	   saves one jump.  This flag is enabled by default at -O and higher.
	   It is not enabled for -Os, since it usually increases code size.

       -ftree-loop-optimize
	   Perform loop optimizations on trees.	 This flag is enabled by
	   default at -O and higher.

       -ftree-loop-linear
	   Perform loop interchange transformations on tree.  Same as
	   -floop-interchange.	To use this code transformation, GCC has to be
	   configured with --with-ppl and --with-cloog to enable the Graphite
	   loop transformation infrastructure.

       -floop-interchange
	   Perform loop interchange transformations on loops.  Interchanging
	   two nested loops switches the inner and outer loops.	 For example,
	   given a loop like:

		   DO J = 1, M
		     DO I = 1, N
		       A(J, I) = A(J, I) * C
		     ENDDO
		   ENDDO

	   loop interchange transforms the loop as if it were written:

		   DO I = 1, N
		     DO J = 1, M
		       A(J, I) = A(J, I) * C
		     ENDDO
		   ENDDO

	   which can be beneficial when "N" is larger than the caches, because
	   in Fortran, the elements of an array are stored in memory
	   contiguously by column, and the original loop iterates over rows,
	   potentially creating at each access a cache miss.  This
	   optimization applies to all the languages supported by GCC and is
	   not limited to Fortran.  To use this code transformation, GCC has
	   to be configured with --with-ppl and --with-cloog to enable the
	   Graphite loop transformation infrastructure.

       -floop-strip-mine
	   Perform loop strip mining transformations on loops.	Strip mining
	   splits a loop into two nested loops.	 The outer loop has strides
	   equal to the strip size and the inner loop has strides of the
	   original loop within a strip.  The strip length can be changed
	   using the loop-block-tile-size parameter.  For example, given a
	   loop like:

		   DO I = 1, N
		     A(I) = A(I) + C
		   ENDDO

	   loop strip mining transforms the loop as if it were written:

		   DO II = 1, N, 51
		     DO I = II, min (II + 50, N)
		       A(I) = A(I) + C
		     ENDDO
		   ENDDO

	   This optimization applies to all the languages supported by GCC and
	   is not limited to Fortran.  To use this code transformation, GCC
	   has to be configured with --with-ppl and --with-cloog to enable the
	   Graphite loop transformation infrastructure.

       -floop-block
	   Perform loop blocking transformations on loops.  Blocking strip
	   mines each loop in the loop nest such that the memory accesses of
	   the element loops fit inside caches.	 The strip length can be
	   changed using the loop-block-tile-size parameter.  For example,
	   given a loop like:

		   DO I = 1, N
		     DO J = 1, M
		       A(J, I) = B(I) + C(J)
		     ENDDO
		   ENDDO

	   loop blocking transforms the loop as if it were written:

		   DO II = 1, N, 51
		     DO JJ = 1, M, 51
		       DO I = II, min (II + 50, N)
			 DO J = JJ, min (JJ + 50, M)
			   A(J, I) = B(I) + C(J)
			 ENDDO
		       ENDDO
		     ENDDO
		   ENDDO

	   which can be beneficial when "M" is larger than the caches, because
	   the innermost loop iterates over a smaller amount of data which can
	   be kept in the caches.  This optimization applies to all the
	   languages supported by GCC and is not limited to Fortran.  To use
	   this code transformation, GCC has to be configured with --with-ppl
	   and --with-cloog to enable the Graphite loop transformation
	   infrastructure.

       -fgraphite-identity
	   Enable the identity transformation for graphite.  For every SCoP we
	   generate the polyhedral representation and transform it back to
	   gimple.  Using -fgraphite-identity we can check the costs or
	   benefits of the GIMPLE -> GRAPHITE -> GIMPLE transformation.	 Some
	   minimal optimizations are also performed by the code generator
	   CLooG, like index splitting and dead code elimination in loops.

       -floop-nest-optimize
	   Enable the ISL based loop nest optimizer.  This is a generic loop
	   nest optimizer based on the Pluto optimization algorithms.  It
	   calculates a loop structure optimized for data-locality and
	   parallelism.	 This option is experimental.

       -floop-parallelize-all
	   Use the Graphite data dependence analysis to identify loops that
	   can be parallelized.	 Parallelize all the loops that can be
	   analyzed to not contain loop carried dependences without checking
	   that it is profitable to parallelize the loops.

       -fcheck-data-deps
	   Compare the results of several data dependence analyzers.  This
	   option is used for debugging the data dependence analyzers.

       -ftree-loop-if-convert
	   Attempt to transform conditional jumps in the innermost loops to
	   branch-less equivalents.  The intent is to remove control-flow from
	   the innermost loops in order to improve the ability of the
	   vectorization pass to handle these loops.  This is enabled by
	   default if vectorization is enabled.

       -ftree-loop-if-convert-stores
	   Attempt to also if-convert conditional jumps containing memory
	   writes.  This transformation can be unsafe for multi-threaded
	   programs as it transforms conditional memory writes into
	   unconditional memory writes.	 For example,

		   for (i = 0; i < N; i++)
		     if (cond)
		       A[i] = expr;

	   is transformed to

		   for (i = 0; i < N; i++)
		     A[i] = cond ? expr : A[i];

	   potentially producing data races.

       -ftree-loop-distribution
	   Perform loop distribution.  This flag can improve cache performance
	   on big loop bodies and allow further loop optimizations, like
	   parallelization or vectorization, to take place.  For example, the
	   loop

		   DO I = 1, N
		     A(I) = B(I) + C
		     D(I) = E(I) * F
		   ENDDO

	   is transformed to

		   DO I = 1, N
		      A(I) = B(I) + C
		   ENDDO
		   DO I = 1, N
		      D(I) = E(I) * F
		   ENDDO

       -ftree-loop-distribute-patterns
	   Perform loop distribution of patterns that can be code generated
	   with calls to a library.  This flag is enabled by default at -O3.

	   This pass distributes the initialization loops and generates a call
	   to memset zero.  For example, the loop

		   DO I = 1, N
		     A(I) = 0
		     B(I) = A(I) + I
		   ENDDO

	   is transformed to

		   DO I = 1, N
		      A(I) = 0
		   ENDDO
		   DO I = 1, N
		      B(I) = A(I) + I
		   ENDDO

	   and the initialization loop is transformed into a call to memset
	   zero.

       -ftree-loop-im
	   Perform loop invariant motion on trees.  This pass moves only
	   invariants that are hard to handle at RTL level (function calls,
	   operations that expand to nontrivial sequences of insns).  With
	   -funswitch-loops it also moves operands of conditions that are
	   invariant out of the loop, so that we can use just trivial
	   invariantness analysis in loop unswitching.	The pass also includes
	   store motion.

       -ftree-loop-ivcanon
	   Create a canonical counter for number of iterations in loops for
	   which determining number of iterations requires complicated
	   analysis.  Later optimizations then may determine the number
	   easily.  Useful especially in connection with unrolling.

       -fivopts
	   Perform induction variable optimizations (strength reduction,
	   induction variable merging and induction variable elimination) on
	   trees.

       -ftree-parallelize-loops=n
	   Parallelize loops, i.e., split their iteration space to run in n
	   threads.  This is only possible for loops whose iterations are
	   independent and can be arbitrarily reordered.  The optimization is
	   only profitable on multiprocessor machines, for loops that are CPU-
	   intensive, rather than constrained e.g. by memory bandwidth.	 This
	   option implies -pthread, and thus is only supported on targets that
	   have support for -pthread.

       -ftree-pta
	   Perform function-local points-to analysis on trees.	This flag is
	   enabled by default at -O and higher.

       -ftree-sra
	   Perform scalar replacement of aggregates.  This pass replaces
	   structure references with scalars to prevent committing structures
	   to memory too early.	 This flag is enabled by default at -O and
	   higher.

       -ftree-copyrename
	   Perform copy renaming on trees.  This pass attempts to rename
	   compiler temporaries to other variables at copy locations, usually
	   resulting in variable names which more closely resemble the
	   original variables.	This flag is enabled by default at -O and
	   higher.

       -ftree-coalesce-inlined-vars
	   Tell the copyrename pass (see -ftree-copyrename) to attempt to
	   combine small user-defined variables too, but only if they were
	   inlined from other functions.  It is a more limited form of
	   -ftree-coalesce-vars.  This may harm debug information of such
	   inlined variables, but it will keep variables of the inlined-into
	   function apart from each other, such that they are more likely to
	   contain the expected values in a debugging session.	This was the
	   default in GCC versions older than 4.7.

       -ftree-coalesce-vars
	   Tell the copyrename pass (see -ftree-copyrename) to attempt to
	   combine small user-defined variables too, instead of just compiler
	   temporaries.	 This may severely limit the ability to debug an
	   optimized program compiled with -fno-var-tracking-assignments.  In
	   the negated form, this flag prevents SSA coalescing of user
	   variables, including inlined ones.  This option is enabled by
	   default.

       -ftree-ter
	   Perform temporary expression replacement during the SSA->normal
	   phase.  Single use/single def temporaries are replaced at their use
	   location with their defining expression.  This results in non-
	   GIMPLE code, but gives the expanders much more complex trees to
	   work on resulting in better RTL generation.	This is enabled by
	   default at -O and higher.

       -ftree-slsr
	   Perform straight-line strength reduction on trees.  This recognizes
	   related expressions involving multiplications and replaces them by
	   less expensive calculations when possible.  This is enabled by
	   default at -O and higher.

       -ftree-vectorize
	   Perform loop vectorization on trees. This flag is enabled by
	   default at -O3.

       -ftree-slp-vectorize
	   Perform basic block vectorization on trees. This flag is enabled by
	   default at -O3 and when -ftree-vectorize is enabled.

       -ftree-vect-loop-version
	   Perform loop versioning when doing loop vectorization on trees.
	   When a loop appears to be vectorizable except that data alignment
	   or data dependence cannot be determined at compile time, then
	   vectorized and non-vectorized versions of the loop are generated
	   along with run-time checks for alignment or dependence to control
	   which version is executed.  This option is enabled by default
	   except at level -Os where it is disabled.

       -fvect-cost-model
	   Enable cost model for vectorization.	 This option is enabled by
	   default at -O3.

       -ftree-vrp
	   Perform Value Range Propagation on trees.  This is similar to the
	   constant propagation pass, but instead of values, ranges of values
	   are propagated.  This allows the optimizers to remove unnecessary
	   range checks like array bound checks and null pointer checks.  This
	   is enabled by default at -O2 and higher.  Null pointer check
	   elimination is only done if -fdelete-null-pointer-checks is
	   enabled.

       -ftracer
	   Perform tail duplication to enlarge superblock size.	 This
	   transformation simplifies the control flow of the function allowing
	   other optimizations to do a better job.

       -funroll-loops
	   Unroll loops whose number of iterations can be determined at
	   compile time or upon entry to the loop.  -funroll-loops implies
	   -frerun-cse-after-loop.  This option makes code larger, and may or
	   may not make it run faster.

       -funroll-all-loops
	   Unroll all loops, even if their number of iterations is uncertain
	   when the loop is entered.  This usually makes programs run more
	   slowly.  -funroll-all-loops implies the same options as
	   -funroll-loops,

       -fsplit-ivs-in-unroller
	   Enables expression of values of induction variables in later
	   iterations of the unrolled loop using the value in the first
	   iteration.  This breaks long dependency chains, thus improving
	   efficiency of the scheduling passes.

	   A combination of -fweb and CSE is often sufficient to obtain the
	   same effect.	 However, that is not reliable in cases where the loop
	   body is more complicated than a single basic block.	It also does
	   not work at all on some architectures due to restrictions in the
	   CSE pass.

	   This optimization is enabled by default.

       -fvariable-expansion-in-unroller
	   With this option, the compiler creates multiple copies of some
	   local variables when unrolling a loop, which can result in superior
	   code.

       -fpartial-inlining
	   Inline parts of functions.  This option has any effect only when
	   inlining itself is turned on by the -finline-functions or
	   -finline-small-functions options.

	   Enabled at level -O2.

       -fpredictive-commoning
	   Perform predictive commoning optimization, i.e., reusing
	   computations (especially memory loads and stores) performed in
	   previous iterations of loops.

	   This option is enabled at level -O3.

       -fprefetch-loop-arrays
	   If supported by the target machine, generate instructions to
	   prefetch memory to improve the performance of loops that access
	   large arrays.

	   This option may generate better or worse code; results are highly
	   dependent on the structure of loops within the source code.

	   Disabled at level -Os.

       -fno-peephole
       -fno-peephole2
	   Disable any machine-specific peephole optimizations.	 The
	   difference between -fno-peephole and -fno-peephole2 is in how they
	   are implemented in the compiler; some targets use one, some use the
	   other, a few use both.

	   -fpeephole is enabled by default.  -fpeephole2 enabled at levels
	   -O2, -O3, -Os.

       -fno-guess-branch-probability
	   Do not guess branch probabilities using heuristics.

	   GCC uses heuristics to guess branch probabilities if they are not
	   provided by profiling feedback (-fprofile-arcs).  These heuristics
	   are based on the control flow graph.	 If some branch probabilities
	   are specified by __builtin_expect, then the heuristics are used to
	   guess branch probabilities for the rest of the control flow graph,
	   taking the __builtin_expect info into account.  The interactions
	   between the heuristics and __builtin_expect can be complex, and in
	   some cases, it may be useful to disable the heuristics so that the
	   effects of __builtin_expect are easier to understand.

	   The default is -fguess-branch-probability at levels -O, -O2, -O3,
	   -Os.

       -freorder-blocks
	   Reorder basic blocks in the compiled function in order to reduce
	   number of taken branches and improve code locality.

	   Enabled at levels -O2, -O3.

       -freorder-blocks-and-partition
	   In addition to reordering basic blocks in the compiled function, in
	   order to reduce number of taken branches, partitions hot and cold
	   basic blocks into separate sections of the assembly and .o files,
	   to improve paging and cache locality performance.

	   This optimization is automatically turned off in the presence of
	   exception handling, for linkonce sections, for functions with a
	   user-defined section attribute and on any architecture that does
	   not support named sections.

       -freorder-functions
	   Reorder functions in the object file in order to improve code
	   locality.  This is implemented by using special subsections
	   ".text.hot" for most frequently executed functions and
	   ".text.unlikely" for unlikely executed functions.  Reordering is
	   done by the linker so object file format must support named
	   sections and linker must place them in a reasonable way.

	   Also profile feedback must be available to make this option
	   effective.  See -fprofile-arcs for details.

	   Enabled at levels -O2, -O3, -Os.

       -fstrict-aliasing
	   Allow the compiler to assume the strictest aliasing rules
	   applicable to the language being compiled.  For C (and C++), this
	   activates optimizations based on the type of expressions.  In
	   particular, an object of one type is assumed never to reside at the
	   same address as an object of a different type, unless the types are
	   almost the same.  For example, an "unsigned int" can alias an
	   "int", but not a "void*" or a "double".  A character type may alias
	   any other type.

	   Pay special attention to code like this:

		   union a_union {
		     int i;
		     double d;
		   };

		   int f() {
		     union a_union t;
		     t.d = 3.0;
		     return t.i;
		   }

	   The practice of reading from a different union member than the one
	   most recently written to (called "type-punning") is common.	Even
	   with -fstrict-aliasing, type-punning is allowed, provided the
	   memory is accessed through the union type.  So, the code above
	   works as expected.	 However, this code might not:

		   int f() {
		     union a_union t;
		     int* ip;
		     t.d = 3.0;
		     ip = &t.i;
		     return *ip;
		   }

	   Similarly, access by taking the address, casting the resulting
	   pointer and dereferencing the result has undefined behavior, even
	   if the cast uses a union type, e.g.:

		   int f() {
		     double d = 3.0;
		     return ((union a_union *) &d)->i;
		   }

	   The -fstrict-aliasing option is enabled at levels -O2, -O3, -Os.

       -fstrict-overflow
	   Allow the compiler to assume strict signed overflow rules,
	   depending on the language being compiled.  For C (and C++) this
	   means that overflow when doing arithmetic with signed numbers is
	   undefined, which means that the compiler may assume that it does
	   not happen.	This permits various optimizations.  For example, the
	   compiler assumes that an expression like "i + 10 > i" is always
	   true for signed "i".	 This assumption is only valid if signed
	   overflow is undefined, as the expression is false if "i + 10"
	   overflows when using twos complement arithmetic.  When this option
	   is in effect any attempt to determine whether an operation on
	   signed numbers overflows must be written carefully to not actually
	   involve overflow.

	   This option also allows the compiler to assume strict pointer
	   semantics: given a pointer to an object, if adding an offset to
	   that pointer does not produce a pointer to the same object, the
	   addition is undefined.  This permits the compiler to conclude that
	   "p + u > p" is always true for a pointer "p" and unsigned integer
	   "u".	 This assumption is only valid because pointer wraparound is
	   undefined, as the expression is false if "p + u" overflows using
	   twos complement arithmetic.

	   See also the -fwrapv option.	 Using -fwrapv means that integer
	   signed overflow is fully defined: it wraps.	When -fwrapv is used,
	   there is no difference between -fstrict-overflow and
	   -fno-strict-overflow for integers.  With -fwrapv certain types of
	   overflow are permitted.  For example, if the compiler gets an
	   overflow when doing arithmetic on constants, the overflowed value
	   can still be used with -fwrapv, but not otherwise.

	   The -fstrict-overflow option is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
	   Align the start of functions to the next power-of-two greater than
	   n, skipping up to n bytes.  For instance, -falign-functions=32
	   aligns functions to the next 32-byte boundary, but
	   -falign-functions=24 aligns to the next 32-byte boundary only if
	   this can be done by skipping 23 bytes or less.

	   -fno-align-functions and -falign-functions=1 are equivalent and
	   mean that functions are not aligned.

	   Some assemblers only support this flag when n is a power of two; in
	   that case, it is rounded up.

	   If n is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -falign-labels
       -falign-labels=n
	   Align all branch targets to a power-of-two boundary, skipping up to
	   n bytes like -falign-functions.  This option can easily make code
	   slower, because it must insert dummy operations for when the branch
	   target is reached in the usual flow of the code.

	   -fno-align-labels and -falign-labels=1 are equivalent and mean that
	   labels are not aligned.

	   If -falign-loops or -falign-jumps are applicable and are greater
	   than this value, then their values are used instead.

	   If n is not specified or is zero, use a machine-dependent default
	   which is very likely to be 1, meaning no alignment.

	   Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
	   Align loops to a power-of-two boundary, skipping up to n bytes like
	   -falign-functions.  If the loops are executed many times, this
	   makes up for any execution of the dummy operations.

	   -fno-align-loops and -falign-loops=1 are equivalent and mean that
	   loops are not aligned.

	   If n is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
	   Align branch targets to a power-of-two boundary, for branch targets
	   where the targets can only be reached by jumping, skipping up to n
	   bytes like -falign-functions.  In this case, no dummy operations
	   need be executed.

	   -fno-align-jumps and -falign-jumps=1 are equivalent and mean that
	   loops are not aligned.

	   If n is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -funit-at-a-time
	   This option is left for compatibility reasons. -funit-at-a-time has
	   no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
	   and -fno-section-anchors.

	   Enabled by default.

       -fno-toplevel-reorder
	   Do not reorder top-level functions, variables, and "asm"
	   statements.	Output them in the same order that they appear in the
	   input file.	When this option is used, unreferenced static
	   variables are not removed.  This option is intended to support
	   existing code that relies on a particular ordering.	For new code,
	   it is better to use attributes.

	   Enabled at level -O0.  When disabled explicitly, it also implies
	   -fno-section-anchors, which is otherwise enabled at -O0 on some
	   targets.

       -fweb
	   Constructs webs as commonly used for register allocation purposes
	   and assign each web individual pseudo register.  This allows the
	   register allocation pass to operate on pseudos directly, but also
	   strengthens several other optimization passes, such as CSE, loop
	   optimizer and trivial dead code remover.  It can, however, make
	   debugging impossible, since variables no longer stay in a "home
	   register".

	   Enabled by default with -funroll-loops.

       -fwhole-program
	   Assume that the current compilation unit represents the whole
	   program being compiled.  All public functions and variables with
	   the exception of "main" and those merged by attribute
	   "externally_visible" become static functions and in effect are
	   optimized more aggressively by interprocedural optimizers.

	   This option should not be used in combination with "-flto".
	   Instead relying on a linker plugin should provide safer and more
	   precise information.

       -flto[=n]
	   This option runs the standard link-time optimizer.  When invoked
	   with source code, it generates GIMPLE (one of GCC's internal
	   representations) and writes it to special ELF sections in the
	   object file.	 When the object files are linked together, all the
	   function bodies are read from these ELF sections and instantiated
	   as if they had been part of the same translation unit.

	   To use the link-time optimizer, -flto needs to be specified at
	   compile time and during the final link.  For example:

		   gcc -c -O2 -flto foo.c
		   gcc -c -O2 -flto bar.c
		   gcc -o myprog -flto -O2 foo.o bar.o

	   The first two invocations to GCC save a bytecode representation of
	   GIMPLE into special ELF sections inside foo.o and bar.o.  The final
	   invocation reads the GIMPLE bytecode from foo.o and bar.o, merges
	   the two files into a single internal image, and compiles the result
	   as usual.  Since both foo.o and bar.o are merged into a single
	   image, this causes all the interprocedural analyses and
	   optimizations in GCC to work across the two files as if they were a
	   single one.	This means, for example, that the inliner is able to
	   inline functions in bar.o into functions in foo.o and vice-versa.

	   Another (simpler) way to enable link-time optimization is:

		   gcc -o myprog -flto -O2 foo.c bar.c

	   The above generates bytecode for foo.c and bar.c, merges them
	   together into a single GIMPLE representation and optimizes them as
	   usual to produce myprog.

	   The only important thing to keep in mind is that to enable link-
	   time optimizations the -flto flag needs to be passed to both the
	   compile and the link commands.

	   To make whole program optimization effective, it is necessary to
	   make certain whole program assumptions.  The compiler needs to know
	   what functions and variables can be accessed by libraries and
	   runtime outside of the link-time optimized unit.  When supported by
	   the linker, the linker plugin (see -fuse-linker-plugin) passes
	   information to the compiler about used and externally visible
	   symbols.  When the linker plugin is not available, -fwhole-program
	   should be used to allow the compiler to make these assumptions,
	   which leads to more aggressive optimization decisions.

	   Note that when a file is compiled with -flto, the generated object
	   file is larger than a regular object file because it contains
	   GIMPLE bytecodes and the usual final code.  This means that object
	   files with LTO information can be linked as normal object files; if
	   -flto is not passed to the linker, no interprocedural optimizations
	   are applied.

	   Additionally, the optimization flags used to compile individual
	   files are not necessarily related to those used at link time.  For
	   instance,

		   gcc -c -O0 -flto foo.c
		   gcc -c -O0 -flto bar.c
		   gcc -o myprog -flto -O3 foo.o bar.o

	   This produces individual object files with unoptimized assembler
	   code, but the resulting binary myprog is optimized at -O3.  If,
	   instead, the final binary is generated without -flto, then myprog
	   is not optimized.

	   When producing the final binary with -flto, GCC only applies link-
	   time optimizations to those files that contain bytecode.
	   Therefore, you can mix and match object files and libraries with
	   GIMPLE bytecodes and final object code.  GCC automatically selects
	   which files to optimize in LTO mode and which files to link without
	   further processing.

	   There are some code generation flags preserved by GCC when
	   generating bytecodes, as they need to be used during the final link
	   stage.  Currently, the following options are saved into the GIMPLE
	   bytecode files: -fPIC, -fcommon and all the -m target flags.

	   At link time, these options are read in and reapplied.  Note that
	   the current implementation makes no attempt to recognize
	   conflicting values for these options.  If different files have
	   conflicting option values (e.g., one file is compiled with -fPIC
	   and another isn't), the compiler simply uses the last value read
	   from the bytecode files.  It is recommended, then, that you compile
	   all the files participating in the same link with the same options.

	   If LTO encounters objects with C linkage declared with incompatible
	   types in separate translation units to be linked together
	   (undefined behavior according to ISO C99 6.2.7), a non-fatal
	   diagnostic may be issued.  The behavior is still undefined at run
	   time.

	   Another feature of LTO is that it is possible to apply
	   interprocedural optimizations on files written in different
	   languages.  This requires support in the language front end.
	   Currently, the C, C++ and Fortran front ends are capable of
	   emitting GIMPLE bytecodes, so something like this should work:

		   gcc -c -flto foo.c
		   g++ -c -flto bar.cc
		   gfortran -c -flto baz.f90
		   g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran

	   Notice that the final link is done with g++ to get the C++ runtime
	   libraries and -lgfortran is added to get the Fortran runtime
	   libraries.  In general, when mixing languages in LTO mode, you
	   should use the same link command options as when mixing languages
	   in a regular (non-LTO) compilation; all you need to add is -flto to
	   all the compile and link commands.

	   If object files containing GIMPLE bytecode are stored in a library
	   archive, say libfoo.a, it is possible to extract and use them in an
	   LTO link if you are using a linker with plugin support.  To enable
	   this feature, use the flag -fuse-linker-plugin at link time:

		   gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo

	   With the linker plugin enabled, the linker extracts the needed
	   GIMPLE files from libfoo.a and passes them on to the running GCC to
	   make them part of the aggregated GIMPLE image to be optimized.

	   If you are not using a linker with plugin support and/or do not
	   enable the linker plugin, then the objects inside libfoo.a are
	   extracted and linked as usual, but they do not participate in the
	   LTO optimization process.

	   Link-time optimizations do not require the presence of the whole
	   program to operate.	If the program does not require any symbols to
	   be exported, it is possible to combine -flto and -fwhole-program to
	   allow the interprocedural optimizers to use more aggressive
	   assumptions which may lead to improved optimization opportunities.
	   Use of -fwhole-program is not needed when linker plugin is active
	   (see -fuse-linker-plugin).

	   The current implementation of LTO makes no attempt to generate
	   bytecode that is portable between different types of hosts.	The
	   bytecode files are versioned and there is a strict version check,
	   so bytecode files generated in one version of GCC will not work
	   with an older/newer version of GCC.

	   Link-time optimization does not work well with generation of
	   debugging information.  Combining -flto with -g is currently
	   experimental and expected to produce wrong results.

	   If you specify the optional n, the optimization and code generation
	   done at link time is executed in parallel using n parallel jobs by
	   utilizing an installed make program.	 The environment variable MAKE
	   may be used to override the program used.  The default value for n
	   is 1.

	   You can also specify -flto=jobserver to use GNU make's job server
	   mode to determine the number of parallel jobs. This is useful when
	   the Makefile calling GCC is already executing in parallel.  You
	   must prepend a + to the command recipe in the parent Makefile for
	   this to work.  This option likely only works if MAKE is GNU make.

	   This option is disabled by default.

       -flto-partition=alg
	   Specify the partitioning algorithm used by the link-time optimizer.
	   The value is either "1to1" to specify a partitioning mirroring the
	   original source files or "balanced" to specify partitioning into
	   equally sized chunks (whenever possible) or "max" to create new
	   partition for every symbol where possible.  Specifying "none" as an
	   algorithm disables partitioning and streaming completely.  The
	   default value is "balanced". While "1to1" can be used as an
	   workaround for various code ordering issues, the "max" partitioning
	   is intended for internal testing only.

       -flto-compression-level=n
	   This option specifies the level of compression used for
	   intermediate language written to LTO object files, and is only
	   meaningful in conjunction with LTO mode (-flto).  Valid values are
	   0 (no compression) to 9 (maximum compression).  Values outside this
	   range are clamped to either 0 or 9.	If the option is not given, a
	   default balanced compression setting is used.

       -flto-report
	   Prints a report with internal details on the workings of the link-
	   time optimizer.  The contents of this report vary from version to
	   version.  It is meant to be useful to GCC developers when
	   processing object files in LTO mode (via -flto).

	   Disabled by default.

       -fuse-linker-plugin
	   Enables the use of a linker plugin during link-time optimization.
	   This option relies on plugin support in the linker, which is
	   available in gold or in GNU ld 2.21 or newer.

	   This option enables the extraction of object files with GIMPLE
	   bytecode out of library archives. This improves the quality of
	   optimization by exposing more code to the link-time optimizer.
	   This information specifies what symbols can be accessed externally
	   (by non-LTO object or during dynamic linking).  Resulting code
	   quality improvements on binaries (and shared libraries that use
	   hidden visibility) are similar to "-fwhole-program".	 See -flto for
	   a description of the effect of this flag and how to use it.

	   This option is enabled by default when LTO support in GCC is
	   enabled and GCC was configured for use with a linker supporting
	   plugins (GNU ld 2.21 or newer or gold).

       -ffat-lto-objects
	   Fat LTO objects are object files that contain both the intermediate
	   language and the object code. This makes them usable for both LTO
	   linking and normal linking. This option is effective only when
	   compiling with -flto and is ignored at link time.

	   -fno-fat-lto-objects improves compilation time over plain LTO, but
	   requires the complete toolchain to be aware of LTO. It requires a
	   linker with linker plugin support for basic functionality.
	   Additionally, nm, ar and ranlib need to support linker plugins to
	   allow a full-featured build environment (capable of building static
	   libraries etc).  GCC provides the gcc-ar, gcc-nm, gcc-ranlib
	   wrappers to pass the right options to these tools. With non fat LTO
	   makefiles need to be modified to use them.

	   The default is -ffat-lto-objects but this default is intended to
	   change in future releases when linker plugin enabled environments
	   become more common.

       -fcompare-elim
	   After register allocation and post-register allocation instruction
	   splitting, identify arithmetic instructions that compute processor
	   flags similar to a comparison operation based on that arithmetic.
	   If possible, eliminate the explicit comparison operation.

	   This pass only applies to certain targets that cannot explicitly
	   represent the comparison operation before register allocation is
	   complete.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fuse-ld=bfd
	   Use the bfd linker instead of the default linker.

       -fuse-ld=gold
	   Use the gold linker instead of the default linker.

       -fcprop-registers
	   After register allocation and post-register allocation instruction
	   splitting, perform a copy-propagation pass to try to reduce
	   scheduling dependencies and occasionally eliminate the copy.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fprofile-correction
	   Profiles collected using an instrumented binary for multi-threaded
	   programs may be inconsistent due to missed counter updates. When
	   this option is specified, GCC uses heuristics to correct or smooth
	   out such inconsistencies. By default, GCC emits an error message
	   when an inconsistent profile is detected.

       -fprofile-dir=path
	   Set the directory to search for the profile data files in to path.
	   This option affects only the profile data generated by
	   -fprofile-generate, -ftest-coverage, -fprofile-arcs and used by
	   -fprofile-use and -fbranch-probabilities and its related options.
	   Both absolute and relative paths can be used.  By default, GCC uses
	   the current directory as path, thus the profile data file appears
	   in the same directory as the object file.

       -fprofile-generate
       -fprofile-generate=path
	   Enable options usually used for instrumenting application to
	   produce profile useful for later recompilation with profile
	   feedback based optimization.	 You must use -fprofile-generate both
	   when compiling and when linking your program.

	   The following options are enabled: "-fprofile-arcs",
	   "-fprofile-values", "-fvpt".

	   If path is specified, GCC looks at the path to find the profile
	   feedback data files. See -fprofile-dir.

       -fprofile-use
       -fprofile-use=path
	   Enable profile feedback directed optimizations, and optimizations
	   generally profitable only with profile feedback available.

	   The following options are enabled: "-fbranch-probabilities",
	   "-fvpt", "-funroll-loops", "-fpeel-loops", "-ftracer",
	   "-ftree-vectorize", "ftree-loop-distribute-patterns"

	   By default, GCC emits an error message if the feedback profiles do
	   not match the source code.  This error can be turned into a warning
	   by using -Wcoverage-mismatch.  Note this may result in poorly
	   optimized code.

	   If path is specified, GCC looks at the path to find the profile
	   feedback data files. See -fprofile-dir.

       The following options control compiler behavior regarding floating-
       point arithmetic.  These options trade off between speed and
       correctness.  All must be specifically enabled.

       -ffloat-store
	   Do not store floating-point variables in registers, and inhibit
	   other options that might change whether a floating-point value is
	   taken from a register or memory.

	   This option prevents undesirable excess precision on machines such
	   as the 68000 where the floating registers (of the 68881) keep more
	   precision than a "double" is supposed to have.  Similarly for the
	   x86 architecture.  For most programs, the excess precision does
	   only good, but a few programs rely on the precise definition of
	   IEEE floating point.	 Use -ffloat-store for such programs, after
	   modifying them to store all pertinent intermediate computations
	   into variables.

       -fexcess-precision=style
	   This option allows further control over excess precision on
	   machines where floating-point registers have more precision than
	   the IEEE "float" and "double" types and the processor does not
	   support operations rounding to those types.	By default,
	   -fexcess-precision=fast is in effect; this means that operations
	   are carried out in the precision of the registers and that it is
	   unpredictable when rounding to the types specified in the source
	   code takes place.  When compiling C, if -fexcess-precision=standard
	   is specified then excess precision follows the rules specified in
	   ISO C99; in particular, both casts and assignments cause values to
	   be rounded to their semantic types (whereas -ffloat-store only
	   affects assignments).  This option is enabled by default for C if a
	   strict conformance option such as -std=c99 is used.

	   -fexcess-precision=standard is not implemented for languages other
	   than C, and has no effect if -funsafe-math-optimizations or
	   -ffast-math is specified.  On the x86, it also has no effect if
	   -mfpmath=sse or -mfpmath=sse+387 is specified; in the former case,
	   IEEE semantics apply without excess precision, and in the latter,
	   rounding is unpredictable.

       -ffast-math
	   Sets -fno-math-errno, -funsafe-math-optimizations,
	   -ffinite-math-only, -fno-rounding-math, -fno-signaling-nans and
	   -fcx-limited-range.

	   This option causes the preprocessor macro "__FAST_MATH__" to be
	   defined.

	   This option is not turned on by any -O option besides -Ofast since
	   it can result in incorrect output for programs that depend on an
	   exact implementation of IEEE or ISO rules/specifications for math
	   functions. It may, however, yield faster code for programs that do
	   not require the guarantees of these specifications.

       -fno-math-errno
	   Do not set "errno" after calling math functions that are executed
	   with a single instruction, e.g., "sqrt".  A program that relies on
	   IEEE exceptions for math error handling may want to use this flag
	   for speed while maintaining IEEE arithmetic compatibility.

	   This option is not turned on by any -O option since it can result
	   in incorrect output for programs that depend on an exact
	   implementation of IEEE or ISO rules/specifications for math
	   functions. It may, however, yield faster code for programs that do
	   not require the guarantees of these specifications.

	   The default is -fmath-errno.

	   On Darwin systems, the math library never sets "errno".  There is
	   therefore no reason for the compiler to consider the possibility
	   that it might, and -fno-math-errno is the default.

       -funsafe-math-optimizations
	   Allow optimizations for floating-point arithmetic that (a) assume
	   that arguments and results are valid and (b) may violate IEEE or
	   ANSI standards.  When used at link-time, it may include libraries
	   or startup files that change the default FPU control word or other
	   similar optimizations.

	   This option is not turned on by any -O option since it can result
	   in incorrect output for programs that depend on an exact
	   implementation of IEEE or ISO rules/specifications for math
	   functions. It may, however, yield faster code for programs that do
	   not require the guarantees of these specifications.	Enables
	   -fno-signed-zeros, -fno-trapping-math, -fassociative-math and
	   -freciprocal-math.

	   The default is -fno-unsafe-math-optimizations.

       -fassociative-math
	   Allow re-association of operands in series of floating-point
	   operations.	This violates the ISO C and C++ language standard by
	   possibly changing computation result.  NOTE: re-ordering may change
	   the sign of zero as well as ignore NaNs and inhibit or create
	   underflow or overflow (and thus cannot be used on code that relies
	   on rounding behavior like "(x + 2**52) - 2**52".  May also reorder
	   floating-point comparisons and thus may not be used when ordered
	   comparisons are required.  This option requires that both
	   -fno-signed-zeros and -fno-trapping-math be in effect.  Moreover,
	   it doesn't make much sense with -frounding-math. For Fortran the
	   option is automatically enabled when both -fno-signed-zeros and
	   -fno-trapping-math are in effect.

	   The default is -fno-associative-math.

       -freciprocal-math
	   Allow the reciprocal of a value to be used instead of dividing by
	   the value if this enables optimizations.  For example "x / y" can
	   be replaced with "x * (1/y)", which is useful if "(1/y)" is subject
	   to common subexpression elimination.	 Note that this loses
	   precision and increases the number of flops operating on the value.

	   The default is -fno-reciprocal-math.

       -ffinite-math-only
	   Allow optimizations for floating-point arithmetic that assume that
	   arguments and results are not NaNs or +-Infs.

	   This option is not turned on by any -O option since it can result
	   in incorrect output for programs that depend on an exact
	   implementation of IEEE or ISO rules/specifications for math
	   functions. It may, however, yield faster code for programs that do
	   not require the guarantees of these specifications.

	   The default is -fno-finite-math-only.

       -fno-signed-zeros
	   Allow optimizations for floating-point arithmetic that ignore the
	   signedness of zero.	IEEE arithmetic specifies the behavior of
	   distinct +0.0 and -0.0 values, which then prohibits simplification
	   of expressions such as x+0.0 or 0.0*x (even with
	   -ffinite-math-only).	 This option implies that the sign of a zero
	   result isn't significant.

	   The default is -fsigned-zeros.

       -fno-trapping-math
	   Compile code assuming that floating-point operations cannot
	   generate user-visible traps.	 These traps include division by zero,
	   overflow, underflow, inexact result and invalid operation.  This
	   option requires that -fno-signaling-nans be in effect.  Setting
	   this option may allow faster code if one relies on "non-stop" IEEE
	   arithmetic, for example.

	   This option should never be turned on by any -O option since it can
	   result in incorrect output for programs that depend on an exact
	   implementation of IEEE or ISO rules/specifications for math
	   functions.

	   The default is -ftrapping-math.

       -frounding-math
	   Disable transformations and optimizations that assume default
	   floating-point rounding behavior.  This is round-to-zero for all
	   floating point to integer conversions, and round-to-nearest for all
	   other arithmetic truncations.  This option should be specified for
	   programs that change the FP rounding mode dynamically, or that may
	   be executed with a non-default rounding mode.  This option disables
	   constant folding of floating-point expressions at compile time
	   (which may be affected by rounding mode) and arithmetic
	   transformations that are unsafe in the presence of sign-dependent
	   rounding modes.

	   The default is -fno-rounding-math.

	   This option is experimental and does not currently guarantee to
	   disable all GCC optimizations that are affected by rounding mode.
	   Future versions of GCC may provide finer control of this setting
	   using C99's "FENV_ACCESS" pragma.  This command-line option will be
	   used to specify the default state for "FENV_ACCESS".

       -fsignaling-nans
	   Compile code assuming that IEEE signaling NaNs may generate user-
	   visible traps during floating-point operations.  Setting this
	   option disables optimizations that may change the number of
	   exceptions visible with signaling NaNs.  This option implies
	   -ftrapping-math.

	   This option causes the preprocessor macro "__SUPPORT_SNAN__" to be
	   defined.

	   The default is -fno-signaling-nans.

	   This option is experimental and does not currently guarantee to
	   disable all GCC optimizations that affect signaling NaN behavior.

       -fsingle-precision-constant
	   Treat floating-point constants as single precision instead of
	   implicitly converting them to double-precision constants.

       -fcx-limited-range
	   When enabled, this option states that a range reduction step is not
	   needed when performing complex division.  Also, there is no
	   checking whether the result of a complex multiplication or division
	   is "NaN + I*NaN", with an attempt to rescue the situation in that
	   case.  The default is -fno-cx-limited-range, but is enabled by
	   -ffast-math.

	   This option controls the default setting of the ISO C99
	   "CX_LIMITED_RANGE" pragma.  Nevertheless, the option applies to all
	   languages.

       -fcx-fortran-rules
	   Complex multiplication and division follow Fortran rules.  Range
	   reduction is done as part of complex division, but there is no
	   checking whether the result of a complex multiplication or division
	   is "NaN + I*NaN", with an attempt to rescue the situation in that
	   case.

	   The default is -fno-cx-fortran-rules.

       The following options control optimizations that may improve
       performance, but are not enabled by any -O options.  This section
       includes experimental options that may produce broken code.

       -fbranch-probabilities
	   After running a program compiled with -fprofile-arcs, you can
	   compile it a second time using -fbranch-probabilities, to improve
	   optimizations based on the number of times each branch was taken.
	   When a program compiled with -fprofile-arcs exits, it saves arc
	   execution counts to a file called sourcename.gcda for each source
	   file.  The information in this data file is very dependent on the
	   structure of the generated code, so you must use the same source
	   code and the same optimization options for both compilations.

	   With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each
	   JUMP_INSN and CALL_INSN.  These can be used to improve
	   optimization.  Currently, they are only used in one place: in
	   reorg.c, instead of guessing which path a branch is most likely to
	   take, the REG_BR_PROB values are used to exactly determine which
	   path is taken more often.

       -fprofile-values
	   If combined with -fprofile-arcs, it adds code so that some data
	   about values of expressions in the program is gathered.

	   With -fbranch-probabilities, it reads back the data gathered from
	   profiling values of expressions for usage in optimizations.

	   Enabled with -fprofile-generate and -fprofile-use.

       -fvpt
	   If combined with -fprofile-arcs, this option instructs the compiler
	   to add code to gather information about values of expressions.

	   With -fbranch-probabilities, it reads back the data gathered and
	   actually performs the optimizations based on them.  Currently the
	   optimizations include specialization of division operations using
	   the knowledge about the value of the denominator.

       -frename-registers
	   Attempt to avoid false dependencies in scheduled code by making use
	   of registers left over after register allocation.  This
	   optimization most benefits processors with lots of registers.
	   Depending on the debug information format adopted by the target,
	   however, it can make debugging impossible, since variables no
	   longer stay in a "home register".

	   Enabled by default with -funroll-loops and -fpeel-loops.

       -ftracer
	   Perform tail duplication to enlarge superblock size.	 This
	   transformation simplifies the control flow of the function allowing
	   other optimizations to do a better job.

	   Enabled with -fprofile-use.

       -funroll-loops
	   Unroll loops whose number of iterations can be determined at
	   compile time or upon entry to the loop.  -funroll-loops implies
	   -frerun-cse-after-loop, -fweb and -frename-registers.  It also
	   turns on complete loop peeling (i.e. complete removal of loops with
	   a small constant number of iterations).  This option makes code
	   larger, and may or may not make it run faster.

	   Enabled with -fprofile-use.

       -funroll-all-loops
	   Unroll all loops, even if their number of iterations is uncertain
	   when the loop is entered.  This usually makes programs run more
	   slowly.  -funroll-all-loops implies the same options as
	   -funroll-loops.

       -fpeel-loops
	   Peels loops for which there is enough information that they do not
	   roll much (from profile feedback).  It also turns on complete loop
	   peeling (i.e. complete removal of loops with small constant number
	   of iterations).

	   Enabled with -fprofile-use.

       -fmove-loop-invariants
	   Enables the loop invariant motion pass in the RTL loop optimizer.
	   Enabled at level -O1

       -funswitch-loops
	   Move branches with loop invariant conditions out of the loop, with
	   duplicates of the loop on both branches (modified according to
	   result of the condition).

       -ffunction-sections
       -fdata-sections
	   Place each function or data item into its own section in the output
	   file if the target supports arbitrary sections.  The name of the
	   function or the name of the data item determines the section's name
	   in the output file.

	   Use these options on systems where the linker can perform
	   optimizations to improve locality of reference in the instruction
	   space.  Most systems using the ELF object format and SPARC
	   processors running Solaris 2 have linkers with such optimizations.
	   AIX may have these optimizations in the future.

	   Only use these options when there are significant benefits from
	   doing so.  When you specify these options, the assembler and linker
	   create larger object and executable files and are also slower.  You
	   cannot use "gprof" on all systems if you specify this option, and
	   you may have problems with debugging if you specify both this
	   option and -g.

       -fbranch-target-load-optimize
	   Perform branch target register load optimization before prologue /
	   epilogue threading.	The use of target registers can typically be
	   exposed only during reload, thus hoisting loads out of loops and
	   doing inter-block scheduling needs a separate optimization pass.

       -fbranch-target-load-optimize2
	   Perform branch target register load optimization after prologue /
	   epilogue threading.

       -fbtr-bb-exclusive
	   When performing branch target register load optimization, don't
	   reuse branch target registers within any basic block.

       -fstack-protector
	   Emit extra code to check for buffer overflows, such as stack
	   smashing attacks.  This is done by adding a guard variable to
	   functions with vulnerable objects.  This includes functions that
	   call "alloca", and functions with buffers larger than 8 bytes.  The
	   guards are initialized when a function is entered and then checked
	   when the function exits.  If a guard check fails, an error message
	   is printed and the program exits.

       -fstack-protector-all
	   Like -fstack-protector except that all functions are protected.

       -fstack-protector-strong
	   Like -fstack-protector but includes additional functions to be
	   protected --- those that have local array definitions, or have
	   references to local frame addresses.

       -fsection-anchors
	   Try to reduce the number of symbolic address calculations by using
	   shared "anchor" symbols to address nearby objects.  This
	   transformation can help to reduce the number of GOT entries and GOT
	   accesses on some targets.

	   For example, the implementation of the following function "foo":

		   static int a, b, c;
		   int foo (void) { return a + b + c; }

	   usually calculates the addresses of all three variables, but if you
	   compile it with -fsection-anchors, it accesses the variables from a
	   common anchor point instead.	 The effect is similar to the
	   following pseudocode (which isn't valid C):

		   int foo (void)
		   {
		     register int *xr = &x;
		     return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
		   }

	   Not all targets support this option.

       --param name=value
	   In some places, GCC uses various constants to control the amount of
	   optimization that is done.  For example, GCC does not inline
	   functions that contain more than a certain number of instructions.
	   You can control some of these constants on the command line using
	   the --param option.

	   The names of specific parameters, and the meaning of the values,
	   are tied to the internals of the compiler, and are subject to
	   change without notice in future releases.

	   In each case, the value is an integer.  The allowable choices for
	   name are:

	   predictable-branch-outcome
	       When branch is predicted to be taken with probability lower
	       than this threshold (in percent), then it is considered well
	       predictable. The default is 10.

	   max-crossjump-edges
	       The maximum number of incoming edges to consider for cross-
	       jumping.	 The algorithm used by -fcrossjumping is O(N^2) in the
	       number of edges incoming to each block.	Increasing values mean
	       more aggressive optimization, making the compilation time
	       increase with probably small improvement in executable size.

	   min-crossjump-insns
	       The minimum number of instructions that must be matched at the
	       end of two blocks before cross-jumping is performed on them.
	       This value is ignored in the case where all instructions in the
	       block being cross-jumped from are matched.  The default value
	       is 5.

	   max-grow-copy-bb-insns
	       The maximum code size expansion factor when copying basic
	       blocks instead of jumping.  The expansion is relative to a jump
	       instruction.  The default value is 8.

	   max-goto-duplication-insns
	       The maximum number of instructions to duplicate to a block that
	       jumps to a computed goto.  To avoid O(N^2) behavior in a number
	       of passes, GCC factors computed gotos early in the compilation
	       process, and unfactors them as late as possible.	 Only computed
	       jumps at the end of a basic blocks with no more than max-goto-
	       duplication-insns are unfactored.  The default value is 8.

	   max-delay-slot-insn-search
	       The maximum number of instructions to consider when looking for
	       an instruction to fill a delay slot.  If more than this
	       arbitrary number of instructions are searched, the time savings
	       from filling the delay slot are minimal, so stop searching.
	       Increasing values mean more aggressive optimization, making the
	       compilation time increase with probably small improvement in
	       execution time.

	   max-delay-slot-live-search
	       When trying to fill delay slots, the maximum number of
	       instructions to consider when searching for a block with valid
	       live register information.  Increasing this arbitrarily chosen
	       value means more aggressive optimization, increasing the
	       compilation time.  This parameter should be removed when the
	       delay slot code is rewritten to maintain the control-flow
	       graph.

	   max-gcse-memory
	       The approximate maximum amount of memory that can be allocated
	       in order to perform the global common subexpression elimination
	       optimization.  If more memory than specified is required, the
	       optimization is not done.

	   max-gcse-insertion-ratio
	       If the ratio of expression insertions to deletions is larger
	       than this value for any expression, then RTL PRE inserts or
	       removes the expression and thus leaves partially redundant
	       computations in the instruction stream.	The default value is
	       20.

	   max-pending-list-length
	       The maximum number of pending dependencies scheduling allows
	       before flushing the current state and starting over.  Large
	       functions with few branches or calls can create excessively
	       large lists which needlessly consume memory and resources.

	   max-modulo-backtrack-attempts
	       The maximum number of backtrack attempts the scheduler should
	       make when modulo scheduling a loop.  Larger values can
	       exponentially increase compilation time.

	   max-inline-insns-single
	       Several parameters control the tree inliner used in GCC.	 This
	       number sets the maximum number of instructions (counted in
	       GCC's internal representation) in a single function that the
	       tree inliner considers for inlining.  This only affects
	       functions declared inline and methods implemented in a class
	       declaration (C++).  The default value is 400.

	   max-inline-insns-auto
	       When you use -finline-functions (included in -O3), a lot of
	       functions that would otherwise not be considered for inlining
	       by the compiler are investigated.  To those functions, a
	       different (more restrictive) limit compared to functions
	       declared inline can be applied.	The default value is 40.

	   inline-min-speedup
	       When estimated performance improvement of caller + callee
	       runtime exceeds this threshold (in precent), the function can
	       be inlined regardless the limit on --param max-inline-insns-
	       single and --param max-inline-insns-auto.

	   large-function-insns
	       The limit specifying really large functions.  For functions
	       larger than this limit after inlining, inlining is constrained
	       by --param large-function-growth.  This parameter is useful
	       primarily to avoid extreme compilation time caused by non-
	       linear algorithms used by the back end.	The default value is
	       2700.

	   large-function-growth
	       Specifies maximal growth of large function caused by inlining
	       in percents.  The default value is 100 which limits large
	       function growth to 2.0 times the original size.

	   large-unit-insns
	       The limit specifying large translation unit.  Growth caused by
	       inlining of units larger than this limit is limited by --param
	       inline-unit-growth.  For small units this might be too tight.
	       For example, consider a unit consisting of function A that is
	       inline and B that just calls A three times.  If B is small
	       relative to A, the growth of unit is 300\% and yet such
	       inlining is very sane.  For very large units consisting of
	       small inlineable functions, however, the overall unit growth
	       limit is needed to avoid exponential explosion of code size.
	       Thus for smaller units, the size is increased to --param large-
	       unit-insns before applying --param inline-unit-growth.  The
	       default is 10000.

	   inline-unit-growth
	       Specifies maximal overall growth of the compilation unit caused
	       by inlining.  The default value is 30 which limits unit growth
	       to 1.3 times the original size.

	   ipcp-unit-growth
	       Specifies maximal overall growth of the compilation unit caused
	       by interprocedural constant propagation.	 The default value is
	       10 which limits unit growth to 1.1 times the original size.

	   large-stack-frame
	       The limit specifying large stack frames.	 While inlining the
	       algorithm is trying to not grow past this limit too much.  The
	       default value is 256 bytes.

	   large-stack-frame-growth
	       Specifies maximal growth of large stack frames caused by
	       inlining in percents.  The default value is 1000 which limits
	       large stack frame growth to 11 times the original size.

	   max-inline-insns-recursive
	   max-inline-insns-recursive-auto
	       Specifies the maximum number of instructions an out-of-line
	       copy of a self-recursive inline function can grow into by
	       performing recursive inlining.

	       For functions declared inline, --param max-inline-insns-
	       recursive is taken into account.	 For functions not declared
	       inline, recursive inlining happens only when -finline-functions
	       (included in -O3) is enabled and --param max-inline-insns-
	       recursive-auto is used.	The default value is 450.

	   max-inline-recursive-depth
	   max-inline-recursive-depth-auto
	       Specifies the maximum recursion depth used for recursive
	       inlining.

	       For functions declared inline, --param max-inline-recursive-
	       depth is taken into account.  For functions not declared
	       inline, recursive inlining happens only when -finline-functions
	       (included in -O3) is enabled and --param max-inline-recursive-
	       depth-auto is used.  The default value is 8.

	   min-inline-recursive-probability
	       Recursive inlining is profitable only for function having deep
	       recursion in average and can hurt for function having little
	       recursion depth by increasing the prologue size or complexity
	       of function body to other optimizers.

	       When profile feedback is available (see -fprofile-generate) the
	       actual recursion depth can be guessed from probability that
	       function recurses via a given call expression.  This parameter
	       limits inlining only to call expressions whose probability
	       exceeds the given threshold (in percents).  The default value
	       is 10.

	   early-inlining-insns
	       Specify growth that the early inliner can make.	In effect it
	       increases the amount of inlining for code having a large
	       abstraction penalty.  The default value is 10.

	   max-early-inliner-iterations
	   max-early-inliner-iterations
	       Limit of iterations of the early inliner.  This basically
	       bounds the number of nested indirect calls the early inliner
	       can resolve.  Deeper chains are still handled by late inlining.

	   comdat-sharing-probability
	   comdat-sharing-probability
	       Probability (in percent) that C++ inline function with comdat
	       visibility are shared across multiple compilation units.	 The
	       default value is 20.

	   min-vect-loop-bound
	       The minimum number of iterations under which loops are not
	       vectorized when -ftree-vectorize is used.  The number of
	       iterations after vectorization needs to be greater than the
	       value specified by this option to allow vectorization.  The
	       default value is 0.

	   gcse-cost-distance-ratio
	       Scaling factor in calculation of maximum distance an expression
	       can be moved by GCSE optimizations.  This is currently
	       supported only in the code hoisting pass.  The bigger the
	       ratio, the more aggressive code hoisting is with simple
	       expressions, i.e., the expressions that have cost less than
	       gcse-unrestricted-cost.	Specifying 0 disables hoisting of
	       simple expressions.  The default value is 10.

	   gcse-unrestricted-cost
	       Cost, roughly measured as the cost of a single typical machine
	       instruction, at which GCSE optimizations do not constrain the
	       distance an expression can travel.  This is currently supported
	       only in the code hoisting pass.	The lesser the cost, the more
	       aggressive code hoisting is.  Specifying 0 allows all
	       expressions to travel unrestricted distances.  The default
	       value is 3.

	   max-hoist-depth
	       The depth of search in the dominator tree for expressions to
	       hoist.  This is used to avoid quadratic behavior in hoisting
	       algorithm.  The value of 0 does not limit on the search, but
	       may slow down compilation of huge functions.  The default value
	       is 30.

	   max-tail-merge-comparisons
	       The maximum amount of similar bbs to compare a bb with.	This
	       is used to avoid quadratic behavior in tree tail merging.  The
	       default value is 10.

	   max-tail-merge-iterations
	       The maximum amount of iterations of the pass over the function.
	       This is used to limit compilation time in tree tail merging.
	       The default value is 2.

	   max-unrolled-insns
	       The maximum number of instructions that a loop may have to be
	       unrolled.  If a loop is unrolled, this parameter also
	       determines how many times the loop code is unrolled.

	   max-average-unrolled-insns
	       The maximum number of instructions biased by probabilities of
	       their execution that a loop may have to be unrolled.  If a loop
	       is unrolled, this parameter also determines how many times the
	       loop code is unrolled.

	   max-unroll-times
	       The maximum number of unrollings of a single loop.

	   max-peeled-insns
	       The maximum number of instructions that a loop may have to be
	       peeled.	If a loop is peeled, this parameter also determines
	       how many times the loop code is peeled.

	   max-peel-times
	       The maximum number of peelings of a single loop.

	   max-peel-branches
	       The maximum number of branches on the hot path through the
	       peeled sequence.

	   max-completely-peeled-insns
	       The maximum number of insns of a completely peeled loop.

	   max-completely-peel-times
	       The maximum number of iterations of a loop to be suitable for
	       complete peeling.

	   max-completely-peel-loop-nest-depth
	       The maximum depth of a loop nest suitable for complete peeling.

	   max-unswitch-insns
	       The maximum number of insns of an unswitched loop.

	   max-unswitch-level
	       The maximum number of branches unswitched in a single loop.

	   lim-expensive
	       The minimum cost of an expensive expression in the loop
	       invariant motion.

	   iv-consider-all-candidates-bound
	       Bound on number of candidates for induction variables, below
	       which all candidates are considered for each use in induction
	       variable optimizations.	If there are more candidates than
	       this, only the most relevant ones are considered to avoid
	       quadratic time complexity.

	   iv-max-considered-uses
	       The induction variable optimizations give up on loops that
	       contain more induction variable uses.

	   iv-always-prune-cand-set-bound
	       If the number of candidates in the set is smaller than this
	       value, always try to remove unnecessary ivs from the set when
	       adding a new one.

	   scev-max-expr-size
	       Bound on size of expressions used in the scalar evolutions
	       analyzer.  Large expressions slow the analyzer.

	   scev-max-expr-complexity
	       Bound on the complexity of the expressions in the scalar
	       evolutions analyzer.  Complex expressions slow the analyzer.

	   omega-max-vars
	       The maximum number of variables in an Omega constraint system.
	       The default value is 128.

	   omega-max-geqs
	       The maximum number of inequalities in an Omega constraint
	       system.	The default value is 256.

	   omega-max-eqs
	       The maximum number of equalities in an Omega constraint system.
	       The default value is 128.

	   omega-max-wild-cards
	       The maximum number of wildcard variables that the Omega solver
	       is able to insert.  The default value is 18.

	   omega-hash-table-size
	       The size of the hash table in the Omega solver.	The default
	       value is 550.

	   omega-max-keys
	       The maximal number of keys used by the Omega solver.  The
	       default value is 500.

	   omega-eliminate-redundant-constraints
	       When set to 1, use expensive methods to eliminate all redundant
	       constraints.  The default value is 0.

	   vect-max-version-for-alignment-checks
	       The maximum number of run-time checks that can be performed
	       when doing loop versioning for alignment in the vectorizer.
	       See option -ftree-vect-loop-version for more information.

	   vect-max-version-for-alias-checks
	       The maximum number of run-time checks that can be performed
	       when doing loop versioning for alias in the vectorizer.	See
	       option -ftree-vect-loop-version for more information.

	   max-iterations-to-track
	       The maximum number of iterations of a loop the brute-force
	       algorithm for analysis of the number of iterations of the loop
	       tries to evaluate.

	   hot-bb-count-ws-permille
	       A basic block profile count is considered hot if it contributes
	       to the given permillage (i.e. 0...1000) of the entire profiled
	       execution.

	   hot-bb-frequency-fraction
	       Select fraction of the entry block frequency of executions of
	       basic block in function given basic block needs to have to be
	       considered hot.

	   max-predicted-iterations
	       The maximum number of loop iterations we predict statically.
	       This is useful in cases where a function contains a single loop
	       with known bound and another loop with unknown bound.  The
	       known number of iterations is predicted correctly, while the
	       unknown number of iterations average to roughly 10.  This means
	       that the loop without bounds appears artificially cold relative
	       to the other one.

	   align-threshold
	       Select fraction of the maximal frequency of executions of a
	       basic block in a function to align the basic block.

	   align-loop-iterations
	       A loop expected to iterate at least the selected number of
	       iterations is aligned.

	   tracer-dynamic-coverage
	   tracer-dynamic-coverage-feedback
	       This value is used to limit superblock formation once the given
	       percentage of executed instructions is covered.	This limits
	       unnecessary code size expansion.

	       The tracer-dynamic-coverage-feedback is used only when profile
	       feedback is available.  The real profiles (as opposed to
	       statically estimated ones) are much less balanced allowing the
	       threshold to be larger value.

	   tracer-max-code-growth
	       Stop tail duplication once code growth has reached given
	       percentage.  This is a rather artificial limit, as most of the
	       duplicates are eliminated later in cross jumping, so it may be
	       set to much higher values than is the desired code growth.

	   tracer-min-branch-ratio
	       Stop reverse growth when the reverse probability of best edge
	       is less than this threshold (in percent).

	   tracer-min-branch-ratio
	   tracer-min-branch-ratio-feedback
	       Stop forward growth if the best edge has probability lower than
	       this threshold.

	       Similarly to tracer-dynamic-coverage two values are present,
	       one for compilation for profile feedback and one for
	       compilation without.  The value for compilation with profile
	       feedback needs to be more conservative (higher) in order to
	       make tracer effective.

	   max-cse-path-length
	       The maximum number of basic blocks on path that CSE considers.
	       The default is 10.

	   max-cse-insns
	       The maximum number of instructions CSE processes before
	       flushing.  The default is 1000.

	   ggc-min-expand
	       GCC uses a garbage collector to manage its own memory
	       allocation.  This parameter specifies the minimum percentage by
	       which the garbage collector's heap should be allowed to expand
	       between collections.  Tuning this may improve compilation
	       speed; it has no effect on code generation.

	       The default is 30% + 70% * (RAM/1GB) with an upper bound of
	       100% when RAM >= 1GB.  If "getrlimit" is available, the notion
	       of "RAM" is the smallest of actual RAM and "RLIMIT_DATA" or
	       "RLIMIT_AS".  If GCC is not able to calculate RAM on a
	       particular platform, the lower bound of 30% is used.  Setting
	       this parameter and ggc-min-heapsize to zero causes a full
	       collection to occur at every opportunity.  This is extremely
	       slow, but can be useful for debugging.

	   ggc-min-heapsize
	       Minimum size of the garbage collector's heap before it begins
	       bothering to collect garbage.  The first collection occurs
	       after the heap expands by ggc-min-expand% beyond ggc-min-
	       heapsize.  Again, tuning this may improve compilation speed,
	       and has no effect on code generation.

	       The default is the smaller of RAM/8, RLIMIT_RSS, or a limit
	       that tries to ensure that RLIMIT_DATA or RLIMIT_AS are not
	       exceeded, but with a lower bound of 4096 (four megabytes) and
	       an upper bound of 131072 (128 megabytes).  If GCC is not able
	       to calculate RAM on a particular platform, the lower bound is
	       used.  Setting this parameter very large effectively disables
	       garbage collection.  Setting this parameter and ggc-min-expand
	       to zero causes a full collection to occur at every opportunity.

	   max-reload-search-insns
	       The maximum number of instruction reload should look backward
	       for equivalent register.	 Increasing values mean more
	       aggressive optimization, making the compilation time increase
	       with probably slightly better performance.  The default value
	       is 100.

	   max-cselib-memory-locations
	       The maximum number of memory locations cselib should take into
	       account.	 Increasing values mean more aggressive optimization,
	       making the compilation time increase with probably slightly
	       better performance.  The default value is 500.

	   reorder-blocks-duplicate
	   reorder-blocks-duplicate-feedback
	       Used by the basic block reordering pass to decide whether to
	       use unconditional branch or duplicate the code on its
	       destination.  Code is duplicated when its estimated size is
	       smaller than this value multiplied by the estimated size of
	       unconditional jump in the hot spots of the program.

	       The reorder-block-duplicate-feedback is used only when profile
	       feedback is available.  It may be set to higher values than
	       reorder-block-duplicate since information about the hot spots
	       is more accurate.

	   max-sched-ready-insns
	       The maximum number of instructions ready to be issued the
	       scheduler should consider at any given time during the first
	       scheduling pass.	 Increasing values mean more thorough
	       searches, making the compilation time increase with probably
	       little benefit.	The default value is 100.

	   max-sched-region-blocks
	       The maximum number of blocks in a region to be considered for
	       interblock scheduling.  The default value is 10.

	   max-pipeline-region-blocks
	       The maximum number of blocks in a region to be considered for
	       pipelining in the selective scheduler.  The default value is
	       15.

	   max-sched-region-insns
	       The maximum number of insns in a region to be considered for
	       interblock scheduling.  The default value is 100.

	   max-pipeline-region-insns
	       The maximum number of insns in a region to be considered for
	       pipelining in the selective scheduler.  The default value is
	       200.

	   min-spec-prob
	       The minimum probability (in percents) of reaching a source
	       block for interblock speculative scheduling.  The default value
	       is 40.

	   max-sched-extend-regions-iters
	       The maximum number of iterations through CFG to extend regions.
	       A value of 0 (the default) disables region extensions.

	   max-sched-insn-conflict-delay
	       The maximum conflict delay for an insn to be considered for
	       speculative motion.  The default value is 3.

	   sched-spec-prob-cutoff
	       The minimal probability of speculation success (in percents),
	       so that speculative insns are scheduled.	 The default value is
	       40.

	   sched-spec-state-edge-prob-cutoff
	       The minimum probability an edge must have for the scheduler to
	       save its state across it.  The default value is 10.

	   sched-mem-true-dep-cost
	       Minimal distance (in CPU cycles) between store and load
	       targeting same memory locations.	 The default value is 1.

	   selsched-max-lookahead
	       The maximum size of the lookahead window of selective
	       scheduling.  It is a depth of search for available
	       instructions.  The default value is 50.

	   selsched-max-sched-times
	       The maximum number of times that an instruction is scheduled
	       during selective scheduling.  This is the limit on the number
	       of iterations through which the instruction may be pipelined.
	       The default value is 2.

	   selsched-max-insns-to-rename
	       The maximum number of best instructions in the ready list that
	       are considered for renaming in the selective scheduler.	The
	       default value is 2.

	   sms-min-sc
	       The minimum value of stage count that swing modulo scheduler
	       generates.  The default value is 2.

	   max-last-value-rtl
	       The maximum size measured as number of RTLs that can be
	       recorded in an expression in combiner for a pseudo register as
	       last known value of that register.  The default is 10000.

	   integer-share-limit
	       Small integer constants can use a shared data structure,
	       reducing the compiler's memory usage and increasing its speed.
	       This sets the maximum value of a shared integer constant.  The
	       default value is 256.

	   ssp-buffer-size
	       The minimum size of buffers (i.e. arrays) that receive stack
	       smashing protection when -fstack-protection is used.

	   max-jump-thread-duplication-stmts
	       Maximum number of statements allowed in a block that needs to
	       be duplicated when threading jumps.

	   max-fields-for-field-sensitive
	       Maximum number of fields in a structure treated in a field
	       sensitive manner during pointer analysis.  The default is zero
	       for -O0 and -O1, and 100 for -Os, -O2, and -O3.

	   prefetch-latency
	       Estimate on average number of instructions that are executed
	       before prefetch finishes.  The distance prefetched ahead is
	       proportional to this constant.  Increasing this number may also
	       lead to less streams being prefetched (see simultaneous-
	       prefetches).

	   simultaneous-prefetches
	       Maximum number of prefetches that can run at the same time.

	   l1-cache-line-size
	       The size of cache line in L1 cache, in bytes.

	   l1-cache-size
	       The size of L1 cache, in kilobytes.

	   l2-cache-size
	       The size of L2 cache, in kilobytes.

	   min-insn-to-prefetch-ratio
	       The minimum ratio between the number of instructions and the
	       number of prefetches to enable prefetching in a loop.

	   prefetch-min-insn-to-mem-ratio
	       The minimum ratio between the number of instructions and the
	       number of memory references to enable prefetching in a loop.

	   use-canonical-types
	       Whether the compiler should use the "canonical" type system.
	       By default, this should always be 1, which uses a more
	       efficient internal mechanism for comparing types in C++ and
	       Objective-C++.  However, if bugs in the canonical type system
	       are causing compilation failures, set this value to 0 to
	       disable canonical types.

	   switch-conversion-max-branch-ratio
	       Switch initialization conversion refuses to create arrays that
	       are bigger than switch-conversion-max-branch-ratio times the
	       number of branches in the switch.

	   max-partial-antic-length
	       Maximum length of the partial antic set computed during the
	       tree partial redundancy elimination optimization (-ftree-pre)
	       when optimizing at -O3 and above.  For some sorts of source
	       code the enhanced partial redundancy elimination optimization
	       can run away, consuming all of the memory available on the host
	       machine.	 This parameter sets a limit on the length of the sets
	       that are computed, which prevents the runaway behavior.
	       Setting a value of 0 for this parameter allows an unlimited set
	       length.

	   sccvn-max-scc-size
	       Maximum size of a strongly connected component (SCC) during
	       SCCVN processing.  If this limit is hit, SCCVN processing for
	       the whole function is not done and optimizations depending on
	       it are disabled.	 The default maximum SCC size is 10000.

	   sccvn-max-alias-queries-per-access
	       Maximum number of alias-oracle queries we perform when looking
	       for redundancies for loads and stores.  If this limit is hit
	       the search is aborted and the load or store is not considered
	       redundant.  The number of queries is algorithmically limited to
	       the number of stores on all paths from the load to the function
	       entry.  The default maxmimum number of queries is 1000.

	   ira-max-loops-num
	       IRA uses regional register allocation by default.  If a
	       function contains more loops than the number given by this
	       parameter, only at most the given number of the most
	       frequently-executed loops form regions for regional register
	       allocation.  The default value of the parameter is 100.

	   ira-max-conflict-table-size
	       Although IRA uses a sophisticated algorithm to compress the
	       conflict table, the table can still require excessive amounts
	       of memory for huge functions.  If the conflict table for a
	       function could be more than the size in MB given by this
	       parameter, the register allocator instead uses a faster,
	       simpler, and lower-quality algorithm that does not require
	       building a pseudo-register conflict table.  The default value
	       of the parameter is 2000.

	   ira-loop-reserved-regs
	       IRA can be used to evaluate more accurate register pressure in
	       loops for decisions to move loop invariants (see -O3).  The
	       number of available registers reserved for some other purposes
	       is given by this parameter.  The default value of the parameter
	       is 2, which is the minimal number of registers needed by
	       typical instructions.  This value is the best found from
	       numerous experiments.

	   loop-invariant-max-bbs-in-loop
	       Loop invariant motion can be very expensive, both in
	       compilation time and in amount of needed compile-time memory,
	       with very large loops.  Loops with more basic blocks than this
	       parameter won't have loop invariant motion optimization
	       performed on them.  The default value of the parameter is 1000
	       for -O1 and 10000 for -O2 and above.

	   loop-max-datarefs-for-datadeps
	       Building data dapendencies is expensive for very large loops.
	       This parameter limits the number of data references in loops
	       that are considered for data dependence analysis.  These large
	       loops are no handled by the optimizations using loop data
	       dependencies.  The default value is 1000.

	   max-vartrack-size
	       Sets a maximum number of hash table slots to use during
	       variable tracking dataflow analysis of any function.  If this
	       limit is exceeded with variable tracking at assignments
	       enabled, analysis for that function is retried without it,
	       after removing all debug insns from the function.  If the limit
	       is exceeded even without debug insns, var tracking analysis is
	       completely disabled for the function.  Setting the parameter to
	       zero makes it unlimited.

	   max-vartrack-expr-depth
	       Sets a maximum number of recursion levels when attempting to
	       map variable names or debug temporaries to value expressions.
	       This trades compilation time for more complete debug
	       information.  If this is set too low, value expressions that
	       are available and could be represented in debug information may
	       end up not being used; setting this higher may enable the
	       compiler to find more complex debug expressions, but compile
	       time and memory use may grow.  The default is 12.

	   min-nondebug-insn-uid
	       Use uids starting at this parameter for nondebug insns.	The
	       range below the parameter is reserved exclusively for debug
	       insns created by -fvar-tracking-assignments, but debug insns
	       may get (non-overlapping) uids above it if the reserved range
	       is exhausted.

	   ipa-sra-ptr-growth-factor
	       IPA-SRA replaces a pointer to an aggregate with one or more new
	       parameters only when their cumulative size is less or equal to
	       ipa-sra-ptr-growth-factor times the size of the original
	       pointer parameter.

	   tm-max-aggregate-size
	       When making copies of thread-local variables in a transaction,
	       this parameter specifies the size in bytes after which
	       variables are saved with the logging functions as opposed to
	       save/restore code sequence pairs.  This option only applies
	       when using -fgnu-tm.

	   graphite-max-nb-scop-params
	       To avoid exponential effects in the Graphite loop transforms,
	       the number of parameters in a Static Control Part (SCoP) is
	       bounded.	 The default value is 10 parameters.  A variable whose
	       value is unknown at compilation time and defined outside a SCoP
	       is a parameter of the SCoP.

	   graphite-max-bbs-per-function
	       To avoid exponential effects in the detection of SCoPs, the
	       size of the functions analyzed by Graphite is bounded.  The
	       default value is 100 basic blocks.

	   loop-block-tile-size
	       Loop blocking or strip mining transforms, enabled with
	       -floop-block or -floop-strip-mine, strip mine each loop in the
	       loop nest by a given number of iterations.  The strip length
	       can be changed using the loop-block-tile-size parameter.	 The
	       default value is 51 iterations.

	   ipa-cp-value-list-size
	       IPA-CP attempts to track all possible values and types passed
	       to a function's parameter in order to propagate them and
	       perform devirtualization.  ipa-cp-value-list-size is the
	       maximum number of values and types it stores per one formal
	       parameter of a function.

	   lto-partitions
	       Specify desired number of partitions produced during WHOPR
	       compilation.  The number of partitions should exceed the number
	       of CPUs used for compilation.  The default value is 32.

	   lto-minpartition
	       Size of minimal partition for WHOPR (in estimated
	       instructions).  This prevents expenses of splitting very small
	       programs into too many partitions.

	   cxx-max-namespaces-for-diagnostic-help
	       The maximum number of namespaces to consult for suggestions
	       when C++ name lookup fails for an identifier.  The default is
	       1000.

	   sink-frequency-threshold
	       The maximum relative execution frequency (in percents) of the
	       target block relative to a statement's original block to allow
	       statement sinking of a statement.  Larger numbers result in
	       more aggressive statement sinking.  The default value is 75.  A
	       small positive adjustment is applied for statements with memory
	       operands as those are even more profitable so sink.

	   max-stores-to-sink
	       The maximum number of conditional stores paires that can be
	       sunk.  Set to 0 if either vectorization (-ftree-vectorize) or
	       if-conversion (-ftree-loop-if-convert) is disabled.  The
	       default is 2.

	   allow-load-data-races
	       Allow optimizers to introduce new data races on loads.  Set to
	       1 to allow, otherwise to 0.  This option is enabled by default
	       unless implicitly set by the -fmemory-model= option.

	   allow-store-data-races
	       Allow optimizers to introduce new data races on stores.	Set to
	       1 to allow, otherwise to 0.  This option is enabled by default
	       unless implicitly set by the -fmemory-model= option.

	   allow-packed-load-data-races
	       Allow optimizers to introduce new data races on packed data
	       loads.  Set to 1 to allow, otherwise to 0.  This option is
	       enabled by default unless implicitly set by the -fmemory-model=
	       option.

	   allow-packed-store-data-races
	       Allow optimizers to introduce new data races on packed data
	       stores.	Set to 1 to allow, otherwise to 0.  This option is
	       enabled by default unless implicitly set by the -fmemory-model=
	       option.

	   case-values-threshold
	       The smallest number of different values for which it is best to
	       use a jump-table instead of a tree of conditional branches.  If
	       the value is 0, use the default for the machine.	 The default
	       is 0.

	   tree-reassoc-width
	       Set the maximum number of instructions executed in parallel in
	       reassociated tree. This parameter overrides target dependent
	       heuristics used by default if has non zero value.

	   sched-pressure-algorithm
	       Choose between the two available implementations of
	       -fsched-pressure.  Algorithm 1 is the original implementation
	       and is the more likely to prevent instructions from being
	       reordered.  Algorithm 2 was designed to be a compromise between
	       the relatively conservative approach taken by algorithm 1 and
	       the rather aggressive approach taken by the default scheduler.
	       It relies more heavily on having a regular register file and
	       accurate register pressure classes.  See haifa-sched.c in the
	       GCC sources for more details.

	       The default choice depends on the target.

	   max-slsr-cand-scan
	       Set the maximum number of existing candidates that will be
	       considered when seeking a basis for a new straight-line
	       strength reduction candidate.

   Options Controlling the Preprocessor
       These options control the C preprocessor, which is run on each C source
       file before actual compilation.

       If you use the -E option, nothing is done except preprocessing.	Some
       of these options make sense only together with -E because they cause
       the preprocessor output to be unsuitable for actual compilation.

       -Wp,option
	   You can use -Wp,option to bypass the compiler driver and pass
	   option directly through to the preprocessor.	 If option contains
	   commas, it is split into multiple options at the commas.  However,
	   many options are modified, translated or interpreted by the
	   compiler driver before being passed to the preprocessor, and -Wp
	   forcibly bypasses this phase.  The preprocessor's direct interface
	   is undocumented and subject to change, so whenever possible you
	   should avoid using -Wp and let the driver handle the options
	   instead.

       -Xpreprocessor option
	   Pass option as an option to the preprocessor.  You can use this to
	   supply system-specific preprocessor options that GCC does not
	   recognize.

	   If you want to pass an option that takes an argument, you must use
	   -Xpreprocessor twice, once for the option and once for the
	   argument.

       -no-integrated-cpp
	   Perform preprocessing as a separate pass before compilation.	 By
	   default, GCC performs preprocessing as an integrated part of input
	   tokenization and parsing.  If this option is provided, the
	   appropriate language front end (cc1, cc1plus, or cc1obj for C, C++,
	   and Objective-C, respectively) is instead invoked twice, once for
	   preprocessing only and once for actual compilation of the
	   preprocessed input.	This option may be useful in conjunction with
	   the -B or -wrapper options to specify an alternate preprocessor or
	   perform additional processing of the program source between normal
	   preprocessing and compilation.

       -D name
	   Predefine name as a macro, with definition 1.

       -D name=definition
	   The contents of definition are tokenized and processed as if they
	   appeared during translation phase three in a #define directive.  In
	   particular, the definition will be truncated by embedded newline
	   characters.

	   If you are invoking the preprocessor from a shell or shell-like
	   program you may need to use the shell's quoting syntax to protect
	   characters such as spaces that have a meaning in the shell syntax.

	   If you wish to define a function-like macro on the command line,
	   write its argument list with surrounding parentheses before the
	   equals sign (if any).  Parentheses are meaningful to most shells,
	   so you will need to quote the option.  With sh and csh,
	   -D'name(args...)=definition' works.

	   -D and -U options are processed in the order they are given on the
	   command line.  All -imacros file and -include file options are
	   processed after all -D and -U options.

       -U name
	   Cancel any previous definition of name, either built in or provided
	   with a -D option.

       -undef
	   Do not predefine any system-specific or GCC-specific macros.	 The
	   standard predefined macros remain defined.

       -I dir
	   Add the directory dir to the list of directories to be searched for
	   header files.  Directories named by -I are searched before the
	   standard system include directories.	 If the directory dir is a
	   standard system include directory, the option is ignored to ensure
	   that the default search order for system directories and the
	   special treatment of system headers are not defeated .  If dir
	   begins with "=", then the "=" will be replaced by the sysroot
	   prefix; see --sysroot and -isysroot.

       -o file
	   Write output to file.  This is the same as specifying file as the
	   second non-option argument to cpp.  gcc has a different
	   interpretation of a second non-option argument, so you must use -o
	   to specify the output file.

       -Wall
	   Turns on all optional warnings which are desirable for normal code.
	   At present this is -Wcomment, -Wtrigraphs, -Wmultichar and a
	   warning about integer promotion causing a change of sign in "#if"
	   expressions.	 Note that many of the preprocessor's warnings are on
	   by default and have no options to control them.

       -Wcomment
       -Wcomments
	   Warn whenever a comment-start sequence /* appears in a /* comment,
	   or whenever a backslash-newline appears in a // comment.  (Both
	   forms have the same effect.)

       -Wtrigraphs
	   Most trigraphs in comments cannot affect the meaning of the
	   program.  However, a trigraph that would form an escaped newline
	   (??/ at the end of a line) can, by changing where the comment
	   begins or ends.  Therefore, only trigraphs that would form escaped
	   newlines produce warnings inside a comment.

	   This option is implied by -Wall.  If -Wall is not given, this
	   option is still enabled unless trigraphs are enabled.  To get
	   trigraph conversion without warnings, but get the other -Wall
	   warnings, use -trigraphs -Wall -Wno-trigraphs.

       -Wtraditional
	   Warn about certain constructs that behave differently in
	   traditional and ISO C.  Also warn about ISO C constructs that have
	   no traditional C equivalent, and problematic constructs which
	   should be avoided.

       -Wundef
	   Warn whenever an identifier which is not a macro is encountered in
	   an #if directive, outside of defined.  Such identifiers are
	   replaced with zero.

       -Wunused-macros
	   Warn about macros defined in the main file that are unused.	A
	   macro is used if it is expanded or tested for existence at least
	   once.  The preprocessor will also warn if the macro has not been
	   used at the time it is redefined or undefined.

	   Built-in macros, macros defined on the command line, and macros
	   defined in include files are not warned about.

	   Note: If a macro is actually used, but only used in skipped
	   conditional blocks, then CPP will report it as unused.  To avoid
	   the warning in such a case, you might improve the scope of the
	   macro's definition by, for example, moving it into the first
	   skipped block.  Alternatively, you could provide a dummy use with
	   something like:

		   #if defined the_macro_causing_the_warning
		   #endif

       -Wendif-labels
	   Warn whenever an #else or an #endif are followed by text.  This
	   usually happens in code of the form

		   #if FOO
		   ...
		   #else FOO
		   ...
		   #endif FOO

	   The second and third "FOO" should be in comments, but often are not
	   in older programs.  This warning is on by default.

       -Werror
	   Make all warnings into hard errors.	Source code which triggers
	   warnings will be rejected.

       -Wsystem-headers
	   Issue warnings for code in system headers.  These are normally
	   unhelpful in finding bugs in your own code, therefore suppressed.
	   If you are responsible for the system library, you may want to see
	   them.

       -w  Suppress all warnings, including those which GNU CPP issues by
	   default.

       -pedantic
	   Issue all the mandatory diagnostics listed in the C standard.  Some
	   of them are left out by default, since they trigger frequently on
	   harmless code.

       -pedantic-errors
	   Issue all the mandatory diagnostics, and make all mandatory
	   diagnostics into errors.  This includes mandatory diagnostics that
	   GCC issues without -pedantic but treats as warnings.

       -M  Instead of outputting the result of preprocessing, output a rule
	   suitable for make describing the dependencies of the main source
	   file.  The preprocessor outputs one make rule containing the object
	   file name for that source file, a colon, and the names of all the
	   included files, including those coming from -include or -imacros
	   command line options.

	   Unless specified explicitly (with -MT or -MQ), the object file name
	   consists of the name of the source file with any suffix replaced
	   with object file suffix and with any leading directory parts
	   removed.  If there are many included files then the rule is split
	   into several lines using \-newline.	The rule has no commands.

	   This option does not suppress the preprocessor's debug output, such
	   as -dM.  To avoid mixing such debug output with the dependency
	   rules you should explicitly specify the dependency output file with
	   -MF, or use an environment variable like DEPENDENCIES_OUTPUT.
	   Debug output will still be sent to the regular output stream as
	   normal.

	   Passing -M to the driver implies -E, and suppresses warnings with
	   an implicit -w.

       -MM Like -M but do not mention header files that are found in system
	   header directories, nor header files that are included, directly or
	   indirectly, from such a header.

	   This implies that the choice of angle brackets or double quotes in
	   an #include directive does not in itself determine whether that
	   header will appear in -MM dependency output.	 This is a slight
	   change in semantics from GCC versions 3.0 and earlier.

       -MF file
	   When used with -M or -MM, specifies a file to write the
	   dependencies to.  If no -MF switch is given the preprocessor sends
	   the rules to the same place it would have sent preprocessed output.

	   When used with the driver options -MD or -MMD, -MF overrides the
	   default dependency output file.

       -MG In conjunction with an option such as -M requesting dependency
	   generation, -MG assumes missing header files are generated files
	   and adds them to the dependency list without raising an error.  The
	   dependency filename is taken directly from the "#include" directive
	   without prepending any path.	 -MG also suppresses preprocessed
	   output, as a missing header file renders this useless.

	   This feature is used in automatic updating of makefiles.

       -MP This option instructs CPP to add a phony target for each dependency
	   other than the main file, causing each to depend on nothing.	 These
	   dummy rules work around errors make gives if you remove header
	   files without updating the Makefile to match.

	   This is typical output:

		   test.o: test.c test.h

		   test.h:

       -MT target
	   Change the target of the rule emitted by dependency generation.  By
	   default CPP takes the name of the main input file, deletes any
	   directory components and any file suffix such as .c, and appends
	   the platform's usual object suffix.	The result is the target.

	   An -MT option will set the target to be exactly the string you
	   specify.  If you want multiple targets, you can specify them as a
	   single argument to -MT, or use multiple -MT options.

	   For example, -MT '$(objpfx)foo.o' might give

		   $(objpfx)foo.o: foo.c

       -MQ target
	   Same as -MT, but it quotes any characters which are special to
	   Make.  -MQ '$(objpfx)foo.o' gives

		   $$(objpfx)foo.o: foo.c

	   The default target is automatically quoted, as if it were given
	   with -MQ.

       -MD -MD is equivalent to -M -MF file, except that -E is not implied.
	   The driver determines file based on whether an -o option is given.
	   If it is, the driver uses its argument but with a suffix of .d,
	   otherwise it takes the name of the input file, removes any
	   directory components and suffix, and applies a .d suffix.

	   If -MD is used in conjunction with -E, any -o switch is understood
	   to specify the dependency output file, but if used without -E, each
	   -o is understood to specify a target object file.

	   Since -E is not implied, -MD can be used to generate a dependency
	   output file as a side-effect of the compilation process.

       -MMD
	   Like -MD except mention only user header files, not system header
	   files.

       -fpch-deps
	   When using precompiled headers, this flag will cause the
	   dependency-output flags to also list the files from the precompiled
	   header's dependencies.  If not specified only the precompiled
	   header would be listed and not the files that were used to create
	   it because those files are not consulted when a precompiled header
	   is used.

       -fpch-preprocess
	   This option allows use of a precompiled header together with -E.
	   It inserts a special "#pragma", "#pragma GCC pch_preprocess
	   "filename"" in the output to mark the place where the precompiled
	   header was found, and its filename.	When -fpreprocessed is in use,
	   GCC recognizes this "#pragma" and loads the PCH.

	   This option is off by default, because the resulting preprocessed
	   output is only really suitable as input to GCC.  It is switched on
	   by -save-temps.

	   You should not write this "#pragma" in your own code, but it is
	   safe to edit the filename if the PCH file is available in a
	   different location.	The filename may be absolute or it may be
	   relative to GCC's current directory.

       -x c
       -x c++
       -x objective-c
       -x assembler-with-cpp
	   Specify the source language: C, C++, Objective-C, or assembly.
	   This has nothing to do with standards conformance or extensions; it
	   merely selects which base syntax to expect.	If you give none of
	   these options, cpp will deduce the language from the extension of
	   the source file: .c, .cc, .m, or .S.	 Some other common extensions
	   for C++ and assembly are also recognized.  If cpp does not
	   recognize the extension, it will treat the file as C; this is the
	   most generic mode.

	   Note: Previous versions of cpp accepted a -lang option which
	   selected both the language and the standards conformance level.
	   This option has been removed, because it conflicts with the -l
	   option.

       -std=standard
       -ansi
	   Specify the standard to which the code should conform.  Currently
	   CPP knows about C and C++ standards; others may be added in the
	   future.

	   standard may be one of:

	   "c90"
	   "c89"
	   "iso9899:1990"
	       The ISO C standard from 1990.  c90 is the customary shorthand
	       for this version of the standard.

	       The -ansi option is equivalent to -std=c90.

	   "iso9899:199409"
	       The 1990 C standard, as amended in 1994.

	   "iso9899:1999"
	   "c99"
	   "iso9899:199x"
	   "c9x"
	       The revised ISO C standard, published in December 1999.	Before
	       publication, this was known as C9X.

	   "iso9899:2011"
	   "c11"
	   "c1x"
	       The revised ISO C standard, published in December 2011.	Before
	       publication, this was known as C1X.

	   "gnu90"
	   "gnu89"
	       The 1990 C standard plus GNU extensions.	 This is the default.

	   "gnu99"
	   "gnu9x"
	       The 1999 C standard plus GNU extensions.

	   "gnu11"
	   "gnu1x"
	       The 2011 C standard plus GNU extensions.

	   "c++98"
	       The 1998 ISO C++ standard plus amendments.

	   "gnu++98"
	       The same as -std=c++98 plus GNU extensions.  This is the
	       default for C++ code.

       -I- Split the include path.  Any directories specified with -I options
	   before -I- are searched only for headers requested with
	   "#include "file""; they are not searched for "#include <file>".  If
	   additional directories are specified with -I options after the -I-,
	   those directories are searched for all #include directives.

	   In addition, -I- inhibits the use of the directory of the current
	   file directory as the first search directory for "#include "file"".
	   This option has been deprecated.

       -nostdinc
	   Do not search the standard system directories for header files.
	   Only the directories you have specified with -I options (and the
	   directory of the current file, if appropriate) are searched.

       -nostdinc++
	   Do not search for header files in the C++-specific standard
	   directories, but do still search the other standard directories.
	   (This option is used when building the C++ library.)

       -include file
	   Process file as if "#include "file"" appeared as the first line of
	   the primary source file.  However, the first directory searched for
	   file is the preprocessor's working directory instead of the
	   directory containing the main source file.  If not found there, it
	   is searched for in the remainder of the "#include "..."" search
	   chain as normal.

	   If multiple -include options are given, the files are included in
	   the order they appear on the command line.

       -imacros file
	   Exactly like -include, except that any output produced by scanning
	   file is thrown away.	 Macros it defines remain defined.  This
	   allows you to acquire all the macros from a header without also
	   processing its declarations.

	   All files specified by -imacros are processed before all files
	   specified by -include.

       -idirafter dir
	   Search dir for header files, but do it after all directories
	   specified with -I and the standard system directories have been
	   exhausted.  dir is treated as a system include directory.  If dir
	   begins with "=", then the "=" will be replaced by the sysroot
	   prefix; see --sysroot and -isysroot.

       -iprefix prefix
	   Specify prefix as the prefix for subsequent -iwithprefix options.
	   If the prefix represents a directory, you should include the final
	   /.

       -iwithprefix dir
       -iwithprefixbefore dir
	   Append dir to the prefix specified previously with -iprefix, and
	   add the resulting directory to the include search path.
	   -iwithprefixbefore puts it in the same place -I would; -iwithprefix
	   puts it where -idirafter would.

       -isysroot dir
	   This option is like the --sysroot option, but applies only to
	   header files (except for Darwin targets, where it applies to both
	   header files and libraries).	 See the --sysroot option for more
	   information.

       -imultilib dir
	   Use dir as a subdirectory of the directory containing target-
	   specific C++ headers.

       -isystem dir
	   Search dir for header files, after all directories specified by -I
	   but before the standard system directories.	Mark it as a system
	   directory, so that it gets the same special treatment as is applied
	   to the standard system directories.	If dir begins with "=", then
	   the "=" will be replaced by the sysroot prefix; see --sysroot and
	   -isysroot.

       -iquote dir
	   Search dir only for header files requested with "#include "file"";
	   they are not searched for "#include <file>", before all directories
	   specified by -I and before the standard system directories.	If dir
	   begins with "=", then the "=" will be replaced by the sysroot
	   prefix; see --sysroot and -isysroot.

       -fdirectives-only
	   When preprocessing, handle directives, but do not expand macros.

	   The option's behavior depends on the -E and -fpreprocessed options.

	   With -E, preprocessing is limited to the handling of directives
	   such as "#define", "#ifdef", and "#error".  Other preprocessor
	   operations, such as macro expansion and trigraph conversion are not
	   performed.  In addition, the -dD option is implicitly enabled.

	   With -fpreprocessed, predefinition of command line and most builtin
	   macros is disabled.	Macros such as "__LINE__", which are
	   contextually dependent, are handled normally.  This enables
	   compilation of files previously preprocessed with "-E
	   -fdirectives-only".

	   With both -E and -fpreprocessed, the rules for -fpreprocessed take
	   precedence.	This enables full preprocessing of files previously
	   preprocessed with "-E -fdirectives-only".

       -fdollars-in-identifiers
	   Accept $ in identifiers.

       -fextended-identifiers
	   Accept universal character names in identifiers.  This option is
	   experimental; in a future version of GCC, it will be enabled by
	   default for C99 and C++.

       -fno-canonical-system-headers
	   When preprocessing, do not shorten system header paths with
	   canonicalization.

       -fpreprocessed
	   Indicate to the preprocessor that the input file has already been
	   preprocessed.  This suppresses things like macro expansion,
	   trigraph conversion, escaped newline splicing, and processing of
	   most directives.  The preprocessor still recognizes and removes
	   comments, so that you can pass a file preprocessed with -C to the
	   compiler without problems.  In this mode the integrated
	   preprocessor is little more than a tokenizer for the front ends.

	   -fpreprocessed is implicit if the input file has one of the
	   extensions .i, .ii or .mi.  These are the extensions that GCC uses
	   for preprocessed files created by -save-temps.

       -ftabstop=width
	   Set the distance between tab stops.	This helps the preprocessor
	   report correct column numbers in warnings or errors, even if tabs
	   appear on the line.	If the value is less than 1 or greater than
	   100, the option is ignored.	The default is 8.

       -fdebug-cpp
	   This option is only useful for debugging GCC.  When used with -E,
	   dumps debugging information about location maps.  Every token in
	   the output is preceded by the dump of the map its location belongs
	   to.	The dump of the map holding the location of a token would be:

		   {"P":F</file/path>;"F":F</includer/path>;"L":<line_num>;"C":<col_num>;"S":<system_header_p>;"M":<map_address>;"E":<macro_expansion_p>,"loc":<location>}

	   When used without -E, this option has no effect.

       -ftrack-macro-expansion[=level]
	   Track locations of tokens across macro expansions. This allows the
	   compiler to emit diagnostic about the current macro expansion stack
	   when a compilation error occurs in a macro expansion. Using this
	   option makes the preprocessor and the compiler consume more memory.
	   The level parameter can be used to choose the level of precision of
	   token location tracking thus decreasing the memory consumption if
	   necessary. Value 0 of level de-activates this option just as if no
	   -ftrack-macro-expansion was present on the command line. Value 1
	   tracks tokens locations in a degraded mode for the sake of minimal
	   memory overhead. In this mode all tokens resulting from the
	   expansion of an argument of a function-like macro have the same
	   location. Value 2 tracks tokens locations completely. This value is
	   the most memory hungry.  When this option is given no argument, the
	   default parameter value is 2.

	   Note that -ftrack-macro-expansion=2 is activated by default.

       -fexec-charset=charset
	   Set the execution character set, used for string and character
	   constants.  The default is UTF-8.  charset can be any encoding
	   supported by the system's "iconv" library routine.

       -fwide-exec-charset=charset
	   Set the wide execution character set, used for wide string and
	   character constants.	 The default is UTF-32 or UTF-16, whichever
	   corresponds to the width of "wchar_t".  As with -fexec-charset,
	   charset can be any encoding supported by the system's "iconv"
	   library routine; however, you will have problems with encodings
	   that do not fit exactly in "wchar_t".

       -finput-charset=charset
	   Set the input character set, used for translation from the
	   character set of the input file to the source character set used by
	   GCC.	 If the locale does not specify, or GCC cannot get this
	   information from the locale, the default is UTF-8.  This can be
	   overridden by either the locale or this command line option.
	   Currently the command line option takes precedence if there's a
	   conflict.  charset can be any encoding supported by the system's
	   "iconv" library routine.

       -fworking-directory
	   Enable generation of linemarkers in the preprocessor output that
	   will let the compiler know the current working directory at the
	   time of preprocessing.  When this option is enabled, the
	   preprocessor will emit, after the initial linemarker, a second
	   linemarker with the current working directory followed by two
	   slashes.  GCC will use this directory, when it's present in the
	   preprocessed input, as the directory emitted as the current working
	   directory in some debugging information formats.  This option is
	   implicitly enabled if debugging information is enabled, but this
	   can be inhibited with the negated form -fno-working-directory.  If
	   the -P flag is present in the command line, this option has no
	   effect, since no "#line" directives are emitted whatsoever.

       -fno-show-column
	   Do not print column numbers in diagnostics.	This may be necessary
	   if diagnostics are being scanned by a program that does not
	   understand the column numbers, such as dejagnu.

       -A predicate=answer
	   Make an assertion with the predicate predicate and answer answer.
	   This form is preferred to the older form -A predicate(answer),
	   which is still supported, because it does not use shell special
	   characters.

       -A -predicate=answer
	   Cancel an assertion with the predicate predicate and answer answer.

       -dCHARS
	   CHARS is a sequence of one or more of the following characters, and
	   must not be preceded by a space.  Other characters are interpreted
	   by the compiler proper, or reserved for future versions of GCC, and
	   so are silently ignored.  If you specify characters whose behavior
	   conflicts, the result is undefined.

	   M   Instead of the normal output, generate a list of #define
	       directives for all the macros defined during the execution of
	       the preprocessor, including predefined macros.  This gives you
	       a way of finding out what is predefined in your version of the
	       preprocessor.  Assuming you have no file foo.h, the command

		       touch foo.h; cpp -dM foo.h

	       will show all the predefined macros.

	       If you use -dM without the -E option, -dM is interpreted as a
	       synonym for -fdump-rtl-mach.

	   D   Like M except in two respects: it does not include the
	       predefined macros, and it outputs both the #define directives
	       and the result of preprocessing.	 Both kinds of output go to
	       the standard output file.

	   N   Like D, but emit only the macro names, not their expansions.

	   I   Output #include directives in addition to the result of
	       preprocessing.

	   U   Like D except that only macros that are expanded, or whose
	       definedness is tested in preprocessor directives, are output;
	       the output is delayed until the use or test of the macro; and
	       #undef directives are also output for macros tested but
	       undefined at the time.

       -P  Inhibit generation of linemarkers in the output from the
	   preprocessor.  This might be useful when running the preprocessor
	   on something that is not C code, and will be sent to a program
	   which might be confused by the linemarkers.

       -C  Do not discard comments.  All comments are passed through to the
	   output file, except for comments in processed directives, which are
	   deleted along with the directive.

	   You should be prepared for side effects when using -C; it causes
	   the preprocessor to treat comments as tokens in their own right.
	   For example, comments appearing at the start of what would be a
	   directive line have the effect of turning that line into an
	   ordinary source line, since the first token on the line is no
	   longer a #.

       -CC Do not discard comments, including during macro expansion.  This is
	   like -C, except that comments contained within macros are also
	   passed through to the output file where the macro is expanded.

	   In addition to the side-effects of the -C option, the -CC option
	   causes all C++-style comments inside a macro to be converted to
	   C-style comments.  This is to prevent later use of that macro from
	   inadvertently commenting out the remainder of the source line.

	   The -CC option is generally used to support lint comments.

       -traditional-cpp
	   Try to imitate the behavior of old-fashioned C preprocessors, as
	   opposed to ISO C preprocessors.

       -trigraphs
	   Process trigraph sequences.	These are three-character sequences,
	   all starting with ??, that are defined by ISO C to stand for single
	   characters.	For example, ??/ stands for \, so '??/n' is a
	   character constant for a newline.  By default, GCC ignores
	   trigraphs, but in standard-conforming modes it converts them.  See
	   the -std and -ansi options.

	   The nine trigraphs and their replacements are

		   Trigraph:	   ??(	??)  ??<  ??>  ??=  ??/	 ??'  ??!  ??-
		   Replacement:	     [	  ]    {    }	 #    \	   ^	|    ~

       -remap
	   Enable special code to work around file systems which only permit
	   very short file names, such as MS-DOS.

       --help
       --target-help
	   Print text describing all the command line options instead of
	   preprocessing anything.

       -v  Verbose mode.  Print out GNU CPP's version number at the beginning
	   of execution, and report the final form of the include path.

       -H  Print the name of each header file used, in addition to other
	   normal activities.  Each name is indented to show how deep in the
	   #include stack it is.  Precompiled header files are also printed,
	   even if they are found to be invalid; an invalid precompiled header
	   file is printed with ...x and a valid one with ...! .

       -version
       --version
	   Print out GNU CPP's version number.	With one dash, proceed to
	   preprocess as normal.  With two dashes, exit immediately.

   Passing Options to the Assembler
       You can pass options to the assembler.

       -Wa,option
	   Pass option as an option to the assembler.  If option contains
	   commas, it is split into multiple options at the commas.

       -Xassembler option
	   Pass option as an option to the assembler.  You can use this to
	   supply system-specific assembler options that GCC does not
	   recognize.

	   If you want to pass an option that takes an argument, you must use
	   -Xassembler twice, once for the option and once for the argument.

   Options for Linking
       These options come into play when the compiler links object files into
       an executable output file.  They are meaningless if the compiler is not
       doing a link step.

       object-file-name
	   A file name that does not end in a special recognized suffix is
	   considered to name an object file or library.  (Object files are
	   distinguished from libraries by the linker according to the file
	   contents.)  If linking is done, these object files are used as
	   input to the linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run, and
	   object file names should not be used as arguments.

       -llibrary
       -l library
	   Search the library named library when linking.  (The second
	   alternative with the library as a separate argument is only for
	   POSIX compliance and is not recommended.)

	   It makes a difference where in the command you write this option;
	   the linker searches and processes libraries and object files in the
	   order they are specified.  Thus, foo.o -lz bar.o searches library z
	   after file foo.o but before bar.o.  If bar.o refers to functions in
	   z, those functions may not be loaded.

	   The linker searches a standard list of directories for the library,
	   which is actually a file named liblibrary.a.	 The linker then uses
	   this file as if it had been specified precisely by name.

	   The directories searched include several standard system
	   directories plus any that you specify with -L.

	   Normally the files found this way are library files---archive files
	   whose members are object files.  The linker handles an archive file
	   by scanning through it for members which define symbols that have
	   so far been referenced but not defined.  But if the file that is
	   found is an ordinary object file, it is linked in the usual
	   fashion.  The only difference between using an -l option and
	   specifying a file name is that -l surrounds library with lib and .a
	   and searches several directories.

       -lobjc
	   You need this special case of the -l option in order to link an
	   Objective-C or Objective-C++ program.

       -nostartfiles
	   Do not use the standard system startup files when linking.  The
	   standard system libraries are used normally, unless -nostdlib or
	   -nodefaultlibs is used.

       -nodefaultlibs
	   Do not use the standard system libraries when linking.  Only the
	   libraries you specify are passed to the linker, and options
	   specifying linkage of the system libraries, such as
	   "-static-libgcc" or "-shared-libgcc", are ignored.  The standard
	   startup files are used normally, unless -nostartfiles is used.

	   The compiler may generate calls to "memcmp", "memset", "memcpy" and
	   "memmove".  These entries are usually resolved by entries in libc.
	   These entry points should be supplied through some other mechanism
	   when this option is specified.

       -nostdlib
	   Do not use the standard system startup files or libraries when
	   linking.  No startup files and only the libraries you specify are
	   passed to the linker, and options specifying linkage of the system
	   libraries, such as "-static-libgcc" or "-shared-libgcc", are
	   ignored.

	   The compiler may generate calls to "memcmp", "memset", "memcpy" and
	   "memmove".  These entries are usually resolved by entries in libc.
	   These entry points should be supplied through some other mechanism
	   when this option is specified.

	   One of the standard libraries bypassed by -nostdlib and
	   -nodefaultlibs is libgcc.a, a library of internal subroutines which
	   GCC uses to overcome shortcomings of particular machines, or
	   special needs for some languages.

	   In most cases, you need libgcc.a even when you want to avoid other
	   standard libraries.	In other words, when you specify -nostdlib or
	   -nodefaultlibs you should usually specify -lgcc as well.  This
	   ensures that you have no unresolved references to internal GCC
	   library subroutines.	 (An example of such an internal subroutine is
	   __main, used to ensure C++ constructors are called.)

       -pie
	   Produce a position independent executable on targets that support
	   it.	For predictable results, you must also specify the same set of
	   options used for compilation (-fpie, -fPIE, or model suboptions)
	   when you specify this linker option.

       -rdynamic
	   Pass the flag -export-dynamic to the ELF linker, on targets that
	   support it. This instructs the linker to add all symbols, not only
	   used ones, to the dynamic symbol table. This option is needed for
	   some uses of "dlopen" or to allow obtaining backtraces from within
	   a program.

       -s  Remove all symbol table and relocation information from the
	   executable.

       -static
	   On systems that support dynamic linking, this prevents linking with
	   the shared libraries.  On other systems, this option has no effect.

       -shared
	   Produce a shared object which can then be linked with other objects
	   to form an executable.  Not all systems support this option.	 For
	   predictable results, you must also specify the same set of options
	   used for compilation (-fpic, -fPIC, or model suboptions) when you
	   specify this linker option.[1]

       -shared-libgcc
       -static-libgcc
	   On systems that provide libgcc as a shared library, these options
	   force the use of either the shared or static version, respectively.
	   If no shared version of libgcc was built when the compiler was
	   configured, these options have no effect.

	   There are several situations in which an application should use the
	   shared libgcc instead of the static version.	 The most common of
	   these is when the application wishes to throw and catch exceptions
	   across different shared libraries.  In that case, each of the
	   libraries as well as the application itself should use the shared
	   libgcc.

	   Therefore, the G++ and GCJ drivers automatically add -shared-libgcc
	   whenever you build a shared library or a main executable, because
	   C++ and Java programs typically use exceptions, so this is the
	   right thing to do.

	   If, instead, you use the GCC driver to create shared libraries, you
	   may find that they are not always linked with the shared libgcc.
	   If GCC finds, at its configuration time, that you have a non-GNU
	   linker or a GNU linker that does not support option --eh-frame-hdr,
	   it links the shared version of libgcc into shared libraries by
	   default.  Otherwise, it takes advantage of the linker and optimizes
	   away the linking with the shared version of libgcc, linking with
	   the static version of libgcc by default.  This allows exceptions to
	   propagate through such shared libraries, without incurring
	   relocation costs at library load time.

	   However, if a library or main executable is supposed to throw or
	   catch exceptions, you must link it using the G++ or GCJ driver, as
	   appropriate for the languages used in the program, or using the
	   option -shared-libgcc, such that it is linked with the shared
	   libgcc.

       -static-libasan
	   When the -fsanitize=address option is used to link a program, the
	   GCC driver automatically links against libasan.  If libasan is
	   available as a shared library, and the -static option is not used,
	   then this links against the shared version of libasan.  The
	   -static-libasan option directs the GCC driver to link libasan
	   statically, without necessarily linking other libraries statically.

       -static-libtsan
	   When the -fsanitize=thread option is used to link a program, the
	   GCC driver automatically links against libtsan.  If libtsan is
	   available as a shared library, and the -static option is not used,
	   then this links against the shared version of libtsan.  The
	   -static-libtsan option directs the GCC driver to link libtsan
	   statically, without necessarily linking other libraries statically.

       -static-libstdc++
	   When the g++ program is used to link a C++ program, it normally
	   automatically links against libstdc++.  If libstdc++ is available
	   as a shared library, and the -static option is not used, then this
	   links against the shared version of libstdc++.  That is normally
	   fine.  However, it is sometimes useful to freeze the version of
	   libstdc++ used by the program without going all the way to a fully
	   static link.	 The -static-libstdc++ option directs the g++ driver
	   to link libstdc++ statically, without necessarily linking other
	   libraries statically.

       -symbolic
	   Bind references to global symbols when building a shared object.
	   Warn about any unresolved references (unless overridden by the link
	   editor option -Xlinker -z -Xlinker defs).  Only a few systems
	   support this option.

       -T script
	   Use script as the linker script.  This option is supported by most
	   systems using the GNU linker.  On some targets, such as bare-board
	   targets without an operating system, the -T option may be required
	   when linking to avoid references to undefined symbols.

       -Xlinker option
	   Pass option as an option to the linker.  You can use this to supply
	   system-specific linker options that GCC does not recognize.

	   If you want to pass an option that takes a separate argument, you
	   must use -Xlinker twice, once for the option and once for the
	   argument.  For example, to pass -assert definitions, you must write
	   -Xlinker -assert -Xlinker definitions.  It does not work to write
	   -Xlinker "-assert definitions", because this passes the entire
	   string as a single argument, which is not what the linker expects.

	   When using the GNU linker, it is usually more convenient to pass
	   arguments to linker options using the option=value syntax than as
	   separate arguments.	For example, you can specify -Xlinker
	   -Map=output.map rather than -Xlinker -Map -Xlinker output.map.
	   Other linkers may not support this syntax for command-line options.

       -Wl,option
	   Pass option as an option to the linker.  If option contains commas,
	   it is split into multiple options at the commas.  You can use this
	   syntax to pass an argument to the option.  For example,
	   -Wl,-Map,output.map passes -Map output.map to the linker.  When
	   using the GNU linker, you can also get the same effect with
	   -Wl,-Map=output.map.

       -u symbol
	   Pretend the symbol symbol is undefined, to force linking of library
	   modules to define it.  You can use -u multiple times with different
	   symbols to force loading of additional library modules.

   Options for Directory Search
       These options specify directories to search for header files, for
       libraries and for parts of the compiler:

       -Idir
	   Add the directory dir to the head of the list of directories to be
	   searched for header files.  This can be used to override a system
	   header file, substituting your own version, since these directories
	   are searched before the system header file directories.  However,
	   you should not use this option to add directories that contain
	   vendor-supplied system header files (use -isystem for that).	 If
	   you use more than one -I option, the directories are scanned in
	   left-to-right order; the standard system directories come after.

	   If a standard system include directory, or a directory specified
	   with -isystem, is also specified with -I, the -I option is ignored.
	   The directory is still searched but as a system directory at its
	   normal position in the system include chain.	 This is to ensure
	   that GCC's procedure to fix buggy system headers and the ordering
	   for the "include_next" directive are not inadvertently changed.  If
	   you really need to change the search order for system directories,
	   use the -nostdinc and/or -isystem options.

       -iplugindir=dir
	   Set the directory to search for plugins that are passed by
	   -fplugin=name instead of -fplugin=path/name.so.  This option is not
	   meant to be used by the user, but only passed by the driver.

       -iquotedir
	   Add the directory dir to the head of the list of directories to be
	   searched for header files only for the case of #include "file";
	   they are not searched for #include <file>, otherwise just like -I.

       -Ldir
	   Add directory dir to the list of directories to be searched for -l.

       -Bprefix
	   This option specifies where to find the executables, libraries,
	   include files, and data files of the compiler itself.

	   The compiler driver program runs one or more of the subprograms
	   cpp, cc1, as and ld.	 It tries prefix as a prefix for each program
	   it tries to run, both with and without machine/version/.

	   For each subprogram to be run, the compiler driver first tries the
	   -B prefix, if any.  If that name is not found, or if -B is not
	   specified, the driver tries two standard prefixes, /usr/lib/gcc/
	   and /usr/local/lib/gcc/.  If neither of those results in a file
	   name that is found, the unmodified program name is searched for
	   using the directories specified in your PATH environment variable.

	   The compiler checks to see if the path provided by the -B refers to
	   a directory, and if necessary it adds a directory separator
	   character at the end of the path.

	   -B prefixes that effectively specify directory names also apply to
	   libraries in the linker, because the compiler translates these
	   options into -L options for the linker.  They also apply to
	   includes files in the preprocessor, because the compiler translates
	   these options into -isystem options for the preprocessor.  In this
	   case, the compiler appends include to the prefix.

	   The runtime support file libgcc.a can also be searched for using
	   the -B prefix, if needed.  If it is not found there, the two
	   standard prefixes above are tried, and that is all.	The file is
	   left out of the link if it is not found by those means.

	   Another way to specify a prefix much like the -B prefix is to use
	   the environment variable GCC_EXEC_PREFIX.

	   As a special kludge, if the path provided by -B is [dir/]stageN/,
	   where N is a number in the range 0 to 9, then it is replaced by
	   [dir/]include.  This is to help with boot-strapping the compiler.

       -specs=file
	   Process file after the compiler reads in the standard specs file,
	   in order to override the defaults which the gcc driver program uses
	   when determining what switches to pass to cc1, cc1plus, as, ld,
	   etc.	 More than one -specs=file can be specified on the command
	   line, and they are processed in order, from left to right.

       --sysroot=dir
	   Use dir as the logical root directory for headers and libraries.
	   For example, if the compiler normally searches for headers in
	   /usr/include and libraries in /usr/lib, it instead searches
	   dir/usr/include and dir/usr/lib.

	   If you use both this option and the -isysroot option, then the
	   --sysroot option applies to libraries, but the -isysroot option
	   applies to header files.

	   The GNU linker (beginning with version 2.16) has the necessary
	   support for this option.  If your linker does not support this
	   option, the header file aspect of --sysroot still works, but the
	   library aspect does not.

       --no-sysroot-suffix
	   For some targets, a suffix is added to the root directory specified
	   with --sysroot, depending on the other options used, so that
	   headers may for example be found in dir/suffix/usr/include instead
	   of dir/usr/include.	This option disables the addition of such a
	   suffix.

       -I- This option has been deprecated.  Please use -iquote instead for -I
	   directories before the -I- and remove the -I-.  Any directories you
	   specify with -I options before the -I- option are searched only for
	   the case of #include "file"; they are not searched for #include
	   <file>.

	   If additional directories are specified with -I options after the
	   -I-, these directories are searched for all #include directives.
	   (Ordinarily all -I directories are used this way.)

	   In addition, the -I- option inhibits the use of the current
	   directory (where the current input file came from) as the first
	   search directory for #include "file".  There is no way to override
	   this effect of -I-.	With -I. you can specify searching the
	   directory that is current when the compiler is invoked.  That is
	   not exactly the same as what the preprocessor does by default, but
	   it is often satisfactory.

	   -I- does not inhibit the use of the standard system directories for
	   header files.  Thus, -I- and -nostdinc are independent.

   Specifying Target Machine and Compiler Version
       The usual way to run GCC is to run the executable called gcc, or
       machine-gcc when cross-compiling, or machine-gcc-version to run a
       version other than the one that was installed last.

   Hardware Models and Configurations
       Each target machine types can have its own special options, starting
       with -m, to choose among various hardware models or
       configurations---for example, 68010 vs 68020, floating coprocessor or
       none.  A single installed version of the compiler can compile for any
       model or configuration, according to the options specified.

       Some configurations of the compiler also support additional special
       options, usually for compatibility with other compilers on the same
       platform.

   AArch64 Options
       These options are defined for AArch64 implementations:

       -mbig-endian
	   Generate big-endian code.  This is the default when GCC is
	   configured for an aarch64_be-*-* target.

       -mgeneral-regs-only
	   Generate code which uses only the general registers.

       -mlittle-endian
	   Generate little-endian code.	 This is the default when GCC is
	   configured for an aarch64-*-* but not an aarch64_be-*-* target.

       -mcmodel=tiny
	   Generate code for the tiny code model.  The program and its
	   statically defined symbols must be within 1GB of each other.
	   Pointers are 64 bits.  Programs can be statically or dynamically
	   linked.  This model is not fully implemented and mostly treated as
	   small.

       -mcmodel=small
	   Generate code for the small code model.  The program and its
	   statically defined symbols must be within 4GB of each other.
	   Pointers are 64 bits.  Programs can be statically or dynamically
	   linked.  This is the default code model.

       -mcmodel=large
	   Generate code for the large code model.  This makes no assumptions
	   about addresses and sizes of sections.  Pointers are 64 bits.
	   Programs can be statically linked only.

       -mstrict-align
	   Do not assume that unaligned memory references will be handled by
	   the system.

       -momit-leaf-frame-pointer
       -mno-omit-leaf-frame-pointer
	   Omit or keep the frame pointer in leaf functions.  The former
	   behaviour is the default.

       -mtls-dialect=desc
	   Use TLS descriptors as the thread-local storage mechanism for
	   dynamic accesses of TLS variables.  This is the default.

       -mtls-dialect=traditional
	   Use traditional TLS as the thread-local storage mechanism for
	   dynamic accesses of TLS variables.

       -march=name
	   Specify the name of the target architecture, optionally suffixed by
	   one or more feature modifiers.  This option has the form
	   -march=arch{+[no]feature}*, where the only value for arch is
	   armv8-a.  The possible values for feature are documented in the
	   sub-section below.

	   Where conflicting feature modifiers are specified, the right-most
	   feature is used.

	   GCC uses this name to determine what kind of instructions it can
	   emit when generating assembly code.	This option can be used in
	   conjunction with or instead of the -mcpu= option.

       -mcpu=name
	   Specify the name of the target processor, optionally suffixed by
	   one or more feature modifiers.  This option has the form
	   -mcpu=cpu{+[no]feature}*, where the possible values for cpu are
	   generic, large.  The possible values for feature are documented in
	   the sub-section below.

	   Where conflicting feature modifiers are specified, the right-most
	   feature is used.

	   GCC uses this name to determine what kind of instructions it can
	   emit when generating assembly code.

       -mtune=name
	   Specify the name of the processor to tune the performance for.  The
	   code will be tuned as if the target processor were of the type
	   specified in this option, but still using instructions compatible
	   with the target processor specified by a -mcpu= option.  This
	   option cannot be suffixed by feature modifiers.

       -march and -mcpu feature modifiers

       Feature modifiers used with -march and -mcpu can be one the following:

       crypto
	   Enable Crypto extension.  This implies Advanced SIMD is enabled.

       fp  Enable floating-point instructions.

       simd
	   Enable Advanced SIMD instructions.  This implies floating-point
	   instructions are enabled.  This is the default for all current
	   possible values for options -march and -mcpu=.

   Adapteva Epiphany Options
       These -m options are defined for Adapteva Epiphany:

       -mhalf-reg-file
	   Don't allocate any register in the range "r32"..."r63".  That
	   allows code to run on hardware variants that lack these registers.

       -mprefer-short-insn-regs
	   Preferrentially allocate registers that allow short instruction
	   generation.	This can result in increased instruction count, so
	   this may either reduce or increase overall code size.

       -mbranch-cost=num
	   Set the cost of branches to roughly num "simple" instructions.
	   This cost is only a heuristic and is not guaranteed to produce
	   consistent results across releases.

       -mcmove
	   Enable the generation of conditional moves.

       -mnops=num
	   Emit num NOPs before every other generated instruction.

       -mno-soft-cmpsf
	   For single-precision floating-point comparisons, emit an "fsub"
	   instruction and test the flags.  This is faster than a software
	   comparison, but can get incorrect results in the presence of NaNs,
	   or when two different small numbers are compared such that their
	   difference is calculated as zero.  The default is -msoft-cmpsf,
	   which uses slower, but IEEE-compliant, software comparisons.

       -mstack-offset=num
	   Set the offset between the top of the stack and the stack pointer.
	   E.g., a value of 8 means that the eight bytes in the range
	   "sp+0...sp+7" can be used by leaf functions without stack
	   allocation.	Values other than 8 or 16 are untested and unlikely to
	   work.  Note also that this option changes the ABI; compiling a
	   program with a different stack offset than the libraries have been
	   compiled with generally does not work.  This option can be useful
	   if you want to evaluate if a different stack offset would give you
	   better code, but to actually use a different stack offset to build
	   working programs, it is recommended to configure the toolchain with
	   the appropriate --with-stack-offset=num option.

       -mno-round-nearest
	   Make the scheduler assume that the rounding mode has been set to
	   truncating.	The default is -mround-nearest.

       -mlong-calls
	   If not otherwise specified by an attribute, assume all calls might
	   be beyond the offset range of the "b" / "bl" instructions, and
	   therefore load the function address into a register before
	   performing a (otherwise direct) call.  This is the default.

       -mshort-calls
	   If not otherwise specified by an attribute, assume all direct calls
	   are in the range of the "b" / "bl" instructions, so use these
	   instructions for direct calls.  The default is -mlong-calls.

       -msmall16
	   Assume addresses can be loaded as 16-bit unsigned values.  This
	   does not apply to function addresses for which -mlong-calls
	   semantics are in effect.

       -mfp-mode=mode
	   Set the prevailing mode of the floating-point unit.	This
	   determines the floating-point mode that is provided and expected at
	   function call and return time.  Making this mode match the mode you
	   predominantly need at function start can make your programs smaller
	   and faster by avoiding unnecessary mode switches.

	   mode can be set to one the following values:

	   caller
	       Any mode at function entry is valid, and retained or restored
	       when the function returns, and when it calls other functions.
	       This mode is useful for compiling libraries or other
	       compilation units you might want to incorporate into different
	       programs with different prevailing FPU modes, and the
	       convenience of being able to use a single object file outweighs
	       the size and speed overhead for any extra mode switching that
	       might be needed, compared with what would be needed with a more
	       specific choice of prevailing FPU mode.

	   truncate
	       This is the mode used for floating-point calculations with
	       truncating (i.e. round towards zero) rounding mode.  That
	       includes conversion from floating point to integer.

	   round-nearest
	       This is the mode used for floating-point calculations with
	       round-to-nearest-or-even rounding mode.

	   int This is the mode used to perform integer calculations in the
	       FPU, e.g.  integer multiply, or integer multiply-and-
	       accumulate.

	   The default is -mfp-mode=caller

       -mnosplit-lohi
       -mno-postinc
       -mno-postmodify
	   Code generation tweaks that disable, respectively, splitting of
	   32-bit loads, generation of post-increment addresses, and
	   generation of post-modify addresses.	 The defaults are msplit-lohi,
	   -mpost-inc, and -mpost-modify.

       -mnovect-double
	   Change the preferred SIMD mode to SImode.  The default is
	   -mvect-double, which uses DImode as preferred SIMD mode.

       -max-vect-align=num
	   The maximum alignment for SIMD vector mode types.  num may be 4 or
	   8.  The default is 8.  Note that this is an ABI change, even though
	   many library function interfaces are unaffected if they don't use
	   SIMD vector modes in places that affect size and/or alignment of
	   relevant types.

       -msplit-vecmove-early
	   Split vector moves into single word moves before reload.  In theory
	   this can give better register allocation, but so far the reverse
	   seems to be generally the case.

       -m1reg-reg
	   Specify a register to hold the constant -1, which makes loading
	   small negative constants and certain bitmasks faster.  Allowable
	   values for reg are r43 and r63, which specify use of that register
	   as a fixed register, and none, which means that no register is used
	   for this purpose.  The default is -m1reg-none.

   ARM Options
       These -m options are defined for Advanced RISC Machines (ARM)
       architectures:

       -mabi=name
	   Generate code for the specified ABI.	 Permissible values are: apcs-
	   gnu, atpcs, aapcs, aapcs-linux and iwmmxt.

       -mapcs-frame
	   Generate a stack frame that is compliant with the ARM Procedure
	   Call Standard for all functions, even if this is not strictly
	   necessary for correct execution of the code.	 Specifying
	   -fomit-frame-pointer with this option causes the stack frames not
	   to be generated for leaf functions.	The default is
	   -mno-apcs-frame.

       -mapcs
	   This is a synonym for -mapcs-frame.

       -mthumb-interwork
	   Generate code that supports calling between the ARM and Thumb
	   instruction sets.  Without this option, on pre-v5 architectures,
	   the two instruction sets cannot be reliably used inside one
	   program.  The default is -mno-thumb-interwork, since slightly
	   larger code is generated when -mthumb-interwork is specified.  In
	   AAPCS configurations this option is meaningless.

       -mno-sched-prolog
	   Prevent the reordering of instructions in the function prologue, or
	   the merging of those instruction with the instructions in the
	   function's body.  This means that all functions start with a
	   recognizable set of instructions (or in fact one of a choice from a
	   small set of different function prologues), and this information
	   can be used to locate the start of functions inside an executable
	   piece of code.  The default is -msched-prolog.

       -mfloat-abi=name
	   Specifies which floating-point ABI to use.  Permissible values are:
	   soft, softfp and hard.

	   Specifying soft causes GCC to generate output containing library
	   calls for floating-point operations.	 softfp allows the generation
	   of code using hardware floating-point instructions, but still uses
	   the soft-float calling conventions.	hard allows generation of
	   floating-point instructions and uses FPU-specific calling
	   conventions.

	   The default depends on the specific target configuration.  Note
	   that the hard-float and soft-float ABIs are not link-compatible;
	   you must compile your entire program with the same ABI, and link
	   with a compatible set of libraries.

       -mlittle-endian
	   Generate code for a processor running in little-endian mode.	 This
	   is the default for all standard configurations.

       -mbig-endian
	   Generate code for a processor running in big-endian mode; the
	   default is to compile code for a little-endian processor.

       -mwords-little-endian
	   This option only applies when generating code for big-endian
	   processors.	Generate code for a little-endian word order but a
	   big-endian byte order.  That is, a byte order of the form 32107654.
	   Note: this option should only be used if you require compatibility
	   with code for big-endian ARM processors generated by versions of
	   the compiler prior to 2.8.  This option is now deprecated.

       -march=name
	   This specifies the name of the target ARM architecture.  GCC uses
	   this name to determine what kind of instructions it can emit when
	   generating assembly code.  This option can be used in conjunction
	   with or instead of the -mcpu= option.  Permissible names are:
	   armv2, armv2a, armv3, armv3m, armv4, armv4t, armv5, armv5t, armv5e,
	   armv5te, armv6, armv6j, armv6t2, armv6z, armv6zk, armv6-m, armv7,
	   armv7-a, armv7-r, armv7-m, armv7e-m armv8-a, iwmmxt, iwmmxt2,
	   ep9312.

	   -march=native causes the compiler to auto-detect the architecture
	   of the build computer.  At present, this feature is only supported
	   on GNU/Linux, and not all architectures are recognized.  If the
	   auto-detect is unsuccessful the option has no effect.

       -mtune=name
	   This option specifies the name of the target ARM processor for
	   which GCC should tune the performance of the code.  For some ARM
	   implementations better performance can be obtained by using this
	   option.  Permissible names are: arm2, arm250, arm3, arm6, arm60,
	   arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di,
	   arm7dmi, arm70, arm700, arm700i, arm710, arm710c, arm7100, arm720,
	   arm7500, arm7500fe, arm7tdmi, arm7tdmi-s, arm710t, arm720t,
	   arm740t, strongarm, strongarm110, strongarm1100, strongarm1110,
	   arm8, arm810, arm9, arm9e, arm920, arm920t, arm922t, arm946e-s,
	   arm966e-s, arm968e-s, arm926ej-s, arm940t, arm9tdmi, arm10tdmi,
	   arm1020t, arm1026ej-s, arm10e, arm1020e, arm1022e, arm1136j-s,
	   arm1136jf-s, mpcore, mpcorenovfp, arm1156t2-s, arm1156t2f-s,
	   arm1176jz-s, arm1176jzf-s, cortex-a5, cortex-a7, cortex-a8,
	   cortex-a9, cortex-a15, cortex-r4, cortex-r4f, cortex-r5, cortex-m4,
	   cortex-m3, cortex-m1, cortex-m0, cortex-m0plus, marvell-pj4,
	   xscale, iwmmxt, iwmmxt2, ep9312, fa526, fa626, fa606te, fa626te,
	   fmp626, fa726te.

	   -mtune=generic-arch specifies that GCC should tune the performance
	   for a blend of processors within architecture arch.	The aim is to
	   generate code that run well on the current most popular processors,
	   balancing between optimizations that benefit some CPUs in the
	   range, and avoiding performance pitfalls of other CPUs.  The
	   effects of this option may change in future GCC versions as CPU
	   models come and go.

	   -mtune=native causes the compiler to auto-detect the CPU of the
	   build computer.  At present, this feature is only supported on
	   GNU/Linux, and not all architectures are recognized.	 If the auto-
	   detect is unsuccessful the option has no effect.

       -mcpu=name
	   This specifies the name of the target ARM processor.	 GCC uses this
	   name to derive the name of the target ARM architecture (as if
	   specified by -march) and the ARM processor type for which to tune
	   for performance (as if specified by -mtune).	 Where this option is
	   used in conjunction with -march or -mtune, those options take
	   precedence over the appropriate part of this option.

	   Permissible names for this option are the same as those for -mtune.

	   -mcpu=generic-arch is also permissible, and is equivalent to
	   -march=arch -mtune=generic-arch.  See -mtune for more information.

	   -mcpu=native causes the compiler to auto-detect the CPU of the
	   build computer.  At present, this feature is only supported on
	   GNU/Linux, and not all architectures are recognized.	 If the auto-
	   detect is unsuccessful the option has no effect.

       -mfpu=name
	   This specifies what floating-point hardware (or hardware emulation)
	   is available on the target.	Permissible names are: vfp, vfpv3,
	   vfpv3-fp16, vfpv3-d16, vfpv3-d16-fp16, vfpv3xd, vfpv3xd-fp16, neon,
	   neon-fp16, vfpv4, vfpv4-d16, fpv4-sp-d16, neon-vfpv4, fp-armv8,
	   neon-fp-armv8, and crypto-neon-fp-armv8.

	   If -msoft-float is specified this specifies the format of floating-
	   point values.

	   If the selected floating-point hardware includes the NEON extension
	   (e.g. -mfpu=neon), note that floating-point operations are not
	   generated by GCC's auto-vectorization pass unless
	   -funsafe-math-optimizations is also specified.  This is because
	   NEON hardware does not fully implement the IEEE 754 standard for
	   floating-point arithmetic (in particular denormal values are
	   treated as zero), so the use of NEON instructions may lead to a
	   loss of precision.

       -mfp16-format=name
	   Specify the format of the "__fp16" half-precision floating-point
	   type.  Permissible names are none, ieee, and alternative; the
	   default is none, in which case the "__fp16" type is not defined.

       -mstructure-size-boundary=n
	   The sizes of all structures and unions are rounded up to a multiple
	   of the number of bits set by this option.  Permissible values are
	   8, 32 and 64.  The default value varies for different toolchains.
	   For the COFF targeted toolchain the default value is 8.  A value of
	   64 is only allowed if the underlying ABI supports it.

	   Specifying a larger number can produce faster, more efficient code,
	   but can also increase the size of the program.  Different values
	   are potentially incompatible.  Code compiled with one value cannot
	   necessarily expect to work with code or libraries compiled with
	   another value, if they exchange information using structures or
	   unions.

       -mabort-on-noreturn
	   Generate a call to the function "abort" at the end of a "noreturn"
	   function.  It is executed if the function tries to return.

       -mlong-calls
       -mno-long-calls
	   Tells the compiler to perform function calls by first loading the
	   address of the function into a register and then performing a
	   subroutine call on this register.  This switch is needed if the
	   target function lies outside of the 64-megabyte addressing range of
	   the offset-based version of subroutine call instruction.

	   Even if this switch is enabled, not all function calls are turned
	   into long calls.  The heuristic is that static functions, functions
	   that have the short-call attribute, functions that are inside the
	   scope of a #pragma no_long_calls directive, and functions whose
	   definitions have already been compiled within the current
	   compilation unit are not turned into long calls.  The exceptions to
	   this rule are that weak function definitions, functions with the
	   long-call attribute or the section attribute, and functions that
	   are within the scope of a #pragma long_calls directive are always
	   turned into long calls.

	   This feature is not enabled by default.  Specifying -mno-long-calls
	   restores the default behavior, as does placing the function calls
	   within the scope of a #pragma long_calls_off directive.  Note these
	   switches have no effect on how the compiler generates code to
	   handle function calls via function pointers.

       -msingle-pic-base
	   Treat the register used for PIC addressing as read-only, rather
	   than loading it in the prologue for each function.  The runtime
	   system is responsible for initializing this register with an
	   appropriate value before execution begins.

       -mpic-register=reg
	   Specify the register to be used for PIC addressing.	For standard
	   PIC base case, the default will be any suitable register determined
	   by compiler.	 For single PIC base case, the default is R9 if target
	   is EABI based or stack-checking is enabled, otherwise the default
	   is R10.

       -mpoke-function-name
	   Write the name of each function into the text section, directly
	   preceding the function prologue.  The generated code is similar to
	   this:

			t0
			    .ascii "arm_poke_function_name", 0
			    .align
			t1
			    .word 0xff000000 + (t1 - t0)
			arm_poke_function_name
			    mov	    ip, sp
			    stmfd   sp!, {fp, ip, lr, pc}
			    sub	    fp, ip, #4

	   When performing a stack backtrace, code can inspect the value of
	   "pc" stored at "fp + 0".  If the trace function then looks at
	   location "pc - 12" and the top 8 bits are set, then we know that
	   there is a function name embedded immediately preceding this
	   location and has length "((pc[-3]) & 0xff000000)".

       -mthumb
       -marm
	   Select between generating code that executes in ARM and Thumb
	   states.  The default for most configurations is to generate code
	   that executes in ARM state, but the default can be changed by
	   configuring GCC with the --with-mode=state configure option.

       -mtpcs-frame
	   Generate a stack frame that is compliant with the Thumb Procedure
	   Call Standard for all non-leaf functions.  (A leaf function is one
	   that does not call any other functions.)  The default is
	   -mno-tpcs-frame.

       -mtpcs-leaf-frame
	   Generate a stack frame that is compliant with the Thumb Procedure
	   Call Standard for all leaf functions.  (A leaf function is one that
	   does not call any other functions.)	The default is
	   -mno-apcs-leaf-frame.

       -mcallee-super-interworking
	   Gives all externally visible functions in the file being compiled
	   an ARM instruction set header which switches to Thumb mode before
	   executing the rest of the function.	This allows these functions to
	   be called from non-interworking code.  This option is not valid in
	   AAPCS configurations because interworking is enabled by default.

       -mcaller-super-interworking
	   Allows calls via function pointers (including virtual functions) to
	   execute correctly regardless of whether the target code has been
	   compiled for interworking or not.  There is a small overhead in the
	   cost of executing a function pointer if this option is enabled.
	   This option is not valid in AAPCS configurations because
	   interworking is enabled by default.

       -mtp=name
	   Specify the access model for the thread local storage pointer.  The
	   valid models are soft, which generates calls to "__aeabi_read_tp",
	   cp15, which fetches the thread pointer from "cp15" directly
	   (supported in the arm6k architecture), and auto, which uses the
	   best available method for the selected processor.  The default
	   setting is auto.

       -mtls-dialect=dialect
	   Specify the dialect to use for accessing thread local storage.  Two
	   dialects are supported---gnu and gnu2.  The gnu dialect selects the
	   original GNU scheme for supporting local and global dynamic TLS
	   models.  The gnu2 dialect selects the GNU descriptor scheme, which
	   provides better performance for shared libraries.  The GNU
	   descriptor scheme is compatible with the original scheme, but does
	   require new assembler, linker and library support.  Initial and
	   local exec TLS models are unaffected by this option and always use
	   the original scheme.

       -mword-relocations
	   Only generate absolute relocations on word-sized values (i.e.
	   R_ARM_ABS32).  This is enabled by default on targets (uClinux,
	   SymbianOS) where the runtime loader imposes this restriction, and
	   when -fpic or -fPIC is specified.

       -mfix-cortex-m3-ldrd
	   Some Cortex-M3 cores can cause data corruption when "ldrd"
	   instructions with overlapping destination and base registers are
	   used.  This option avoids generating these instructions.  This
	   option is enabled by default when -mcpu=cortex-m3 is specified.

       -munaligned-access
       -mno-unaligned-access
	   Enables (or disables) reading and writing of 16- and 32- bit values
	   from addresses that are not 16- or 32- bit aligned.	By default
	   unaligned access is disabled for all pre-ARMv6 and all ARMv6-M
	   architectures, and enabled for all other architectures.  If
	   unaligned access is not enabled then words in packed data
	   structures will be accessed a byte at a time.

	   The ARM attribute "Tag_CPU_unaligned_access" will be set in the
	   generated object file to either true or false, depending upon the
	   setting of this option.  If unaligned access is enabled then the
	   preprocessor symbol "__ARM_FEATURE_UNALIGNED" will also be defined.

   AVR Options
       These options are defined for AVR implementations:

       -mmcu=mcu
	   Specify Atmel AVR instruction set architectures (ISA) or MCU type.

	   The default for this option is@tie{}"avr2".

	   GCC supports the following AVR devices and ISAs:

	   "avr2"
	       "Classic" devices with up to 8@tie{}KiB of program memory.
	       mcu@tie{}= "attiny22", "attiny26", "at90c8534", "at90s2313",
	       "at90s2323", "at90s2333", "at90s2343", "at90s4414",
	       "at90s4433", "at90s4434", "at90s8515", "at90s8535".

	   "avr25"
	       "Classic" devices with up to 8@tie{}KiB of program memory and
	       with the "MOVW" instruction.  mcu@tie{}= "ata5272", "ata6289",
	       "attiny13", "attiny13a", "attiny2313", "attiny2313a",
	       "attiny24", "attiny24a", "attiny25", "attiny261", "attiny261a",
	       "attiny43u", "attiny4313", "attiny44", "attiny44a", "attiny45",
	       "attiny461", "attiny461a", "attiny48", "attiny84", "attiny84a",
	       "attiny85", "attiny861", "attiny861a", "attiny87", "attiny88",
	       "at86rf401".

	   "avr3"
	       "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB of
	       program memory.	mcu@tie{}= "at43usb355", "at76c711".

	   "avr31"
	       "Classic" devices with 128@tie{}KiB of program memory.
	       mcu@tie{}= "atmega103", "at43usb320".

	   "avr35"
	       "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB of program
	       memory and with the "MOVW" instruction.	mcu@tie{}= "ata5505",
	       "atmega16u2", "atmega32u2", "atmega8u2", "attiny1634",
	       "attiny167", "at90usb162", "at90usb82".

	   "avr4"
	       "Enhanced" devices with up to 8@tie{}KiB of program memory.
	       mcu@tie{}= "ata6285", "ata6286", "atmega48", "atmega48a",
	       "atmega48p", "atmega48pa", "atmega8", "atmega8a", "atmega8hva",
	       "atmega8515", "atmega8535", "atmega88", "atmega88a",
	       "atmega88p", "atmega88pa", "at90pwm1", "at90pwm2", "at90pwm2b",
	       "at90pwm3", "at90pwm3b", "at90pwm81".

	   "avr5"
	       "Enhanced" devices with 16@tie{}KiB up to 64@tie{}KiB of
	       program memory.	mcu@tie{}= "ata5790", "ata5790n", "ata5795",
	       "atmega16", "atmega16a", "atmega16hva", "atmega16hva2",
	       "atmega16hvb", "atmega16hvbrevb", "atmega16m1", "atmega16u4",
	       "atmega161", "atmega162", "atmega163", "atmega164a",
	       "atmega164p", "atmega164pa", "atmega165", "atmega165a",
	       "atmega165p", "atmega165pa", "atmega168", "atmega168a",
	       "atmega168p", "atmega168pa", "atmega169", "atmega169a",
	       "atmega169p", "atmega169pa", "atmega26hvg", "atmega32",
	       "atmega32a", "atmega32c1", "atmega32hvb", "atmega32hvbrevb",
	       "atmega32m1", "atmega32u4", "atmega32u6", "atmega323",
	       "atmega324a", "atmega324p", "atmega324pa", "atmega325",
	       "atmega325a", "atmega325p", "atmega3250", "atmega3250a",
	       "atmega3250p", "atmega3250pa", "atmega328", "atmega328p",
	       "atmega329", "atmega329a", "atmega329p", "atmega329pa",
	       "atmega3290", "atmega3290a", "atmega3290p", "atmega3290pa",
	       "atmega406", "atmega48hvf", "atmega64", "atmega64a",
	       "atmega64c1", "atmega64hve", "atmega64m1", "atmega64rfa2",
	       "atmega64rfr2", "atmega640", "atmega644", "atmega644a",
	       "atmega644p", "atmega644pa", "atmega645", "atmega645a",
	       "atmega645p", "atmega6450", "atmega6450a", "atmega6450p",
	       "atmega649", "atmega649a", "atmega649p", "atmega6490",
	       "atmega6490a", "atmega6490p", "at90can32", "at90can64",
	       "at90pwm161", "at90pwm216", "at90pwm316", "at90scr100",
	       "at90usb646", "at90usb647", "at94k", "m3000".

	   "avr51"
	       "Enhanced" devices with 128@tie{}KiB of program memory.
	       mcu@tie{}= "atmega128", "atmega128a", "atmega128rfa1",
	       "atmega1280", "atmega1281", "atmega1284", "atmega1284p",
	       "at90can128", "at90usb1286", "at90usb1287".

	   "avr6"
	       "Enhanced" devices with 3-byte PC, i.e. with more than
	       128@tie{}KiB of program memory.	mcu@tie{}= "atmega2560",
	       "atmega2561".

	   "avrxmega2"
	       "XMEGA" devices with more than 8@tie{}KiB and up to 64@tie{}KiB
	       of program memory.  mcu@tie{}= "atmxt112sl", "atmxt224",
	       "atmxt224e", "atmxt336s", "atxmega16a4", "atxmega16a4u",
	       "atxmega16c4", "atxmega16d4", "atxmega16x1", "atxmega32a4",
	       "atxmega32a4u", "atxmega32c4", "atxmega32d4", "atxmega32e5",
	       "atxmega32x1".

	   "avrxmega4"
	       "XMEGA" devices with more than 64@tie{}KiB and up to
	       128@tie{}KiB of program memory.	mcu@tie{}= "atxmega64a3",
	       "atxmega64a3u", "atxmega64a4u", "atxmega64b1", "atxmega64b3",
	       "atxmega64c3", "atxmega64d3", "atxmega64d4".

	   "avrxmega5"
	       "XMEGA" devices with more than 64@tie{}KiB and up to
	       128@tie{}KiB of program memory and more than 64@tie{}KiB of
	       RAM.  mcu@tie{}= "atxmega64a1", "atxmega64a1u".

	   "avrxmega6"
	       "XMEGA" devices with more than 128@tie{}KiB of program memory.
	       mcu@tie{}= "atmxt540s", "atmxt540sreva", "atxmega128a3",
	       "atxmega128a3u", "atxmega128b1", "atxmega128b3",
	       "atxmega128c3", "atxmega128d3", "atxmega128d4", "atxmega192a3",
	       "atxmega192a3u", "atxmega192c3", "atxmega192d3",
	       "atxmega256a3", "atxmega256a3b", "atxmega256a3bu",
	       "atxmega256a3u", "atxmega256c3", "atxmega256d3",
	       "atxmega384c3", "atxmega384d3".

	   "avrxmega7"
	       "XMEGA" devices with more than 128@tie{}KiB of program memory
	       and more than 64@tie{}KiB of RAM.  mcu@tie{}= "atxmega128a1",
	       "atxmega128a1u", "atxmega128a4u".

	   "avr1"
	       This ISA is implemented by the minimal AVR core and supported
	       for assembler only.  mcu@tie{}= "attiny11", "attiny12",
	       "attiny15", "attiny28", "at90s1200".

       -maccumulate-args
	   Accumulate outgoing function arguments and acquire/release the
	   needed stack space for outgoing function arguments once in function
	   prologue/epilogue.  Without this option, outgoing arguments are
	   pushed before calling a function and popped afterwards.

	   Popping the arguments after the function call can be expensive on
	   AVR so that accumulating the stack space might lead to smaller
	   executables because arguments need not to be removed from the stack
	   after such a function call.

	   This option can lead to reduced code size for functions that
	   perform several calls to functions that get their arguments on the
	   stack like calls to printf-like functions.

       -mbranch-cost=cost
	   Set the branch costs for conditional branch instructions to cost.
	   Reasonable values for cost are small, non-negative integers. The
	   default branch cost is 0.

       -mcall-prologues
	   Functions prologues/epilogues are expanded as calls to appropriate
	   subroutines.	 Code size is smaller.

       -mint8
	   Assume "int" to be 8-bit integer.  This affects the sizes of all
	   types: a "char" is 1 byte, an "int" is 1 byte, a "long" is 2 bytes,
	   and "long long" is 4 bytes.	Please note that this option does not
	   conform to the C standards, but it results in smaller code size.

       -mno-interrupts
	   Generated code is not compatible with hardware interrupts.  Code
	   size is smaller.

       -mrelax
	   Try to replace "CALL" resp. "JMP" instruction by the shorter
	   "RCALL" resp. "RJMP" instruction if applicable.  Setting "-mrelax"
	   just adds the "--relax" option to the linker command line when the
	   linker is called.

	   Jump relaxing is performed by the linker because jump offsets are
	   not known before code is located. Therefore, the assembler code
	   generated by the compiler is the same, but the instructions in the
	   executable may differ from instructions in the assembler code.

	   Relaxing must be turned on if linker stubs are needed, see the
	   section on "EIND" and linker stubs below.

       -msp8
	   Treat the stack pointer register as an 8-bit register, i.e. assume
	   the high byte of the stack pointer is zero.	In general, you don't
	   need to set this option by hand.

	   This option is used internally by the compiler to select and build
	   multilibs for architectures "avr2" and "avr25".  These
	   architectures mix devices with and without "SPH".  For any setting
	   other than "-mmcu=avr2" or "-mmcu=avr25" the compiler driver will
	   add or remove this option from the compiler proper's command line,
	   because the compiler then knows if the device or architecture has
	   an 8-bit stack pointer and thus no "SPH" register or not.

       -mstrict-X
	   Use address register "X" in a way proposed by the hardware.	This
	   means that "X" is only used in indirect, post-increment or pre-
	   decrement addressing.

	   Without this option, the "X" register may be used in the same way
	   as "Y" or "Z" which then is emulated by additional instructions.
	   For example, loading a value with "X+const" addressing with a small
	   non-negative "const < 64" to a register Rn is performed as

		   adiw r26, const   ; X += const
		   ld	<Rn>, X	       ; <Rn> = *X
		   sbiw r26, const   ; X -= const

       -mtiny-stack
	   Only change the lower 8@tie{}bits of the stack pointer.

       -Waddr-space-convert
	   Warn about conversions between address spaces in the case where the
	   resulting address space is not contained in the incoming address
	   space.

       "EIND" and Devices with more than 128 Ki Bytes of Flash

       Pointers in the implementation are 16@tie{}bits wide.  The address of a
       function or label is represented as word address so that indirect jumps
       and calls can target any code address in the range of 64@tie{}Ki words.

       In order to facilitate indirect jump on devices with more than
       128@tie{}Ki bytes of program memory space, there is a special function
       register called "EIND" that serves as most significant part of the
       target address when "EICALL" or "EIJMP" instructions are used.

       Indirect jumps and calls on these devices are handled as follows by the
       compiler and are subject to some limitations:

       o   The compiler never sets "EIND".

       o   The compiler uses "EIND" implicitely in "EICALL"/"EIJMP"
	   instructions or might read "EIND" directly in order to emulate an
	   indirect call/jump by means of a "RET" instruction.

       o   The compiler assumes that "EIND" never changes during the startup
	   code or during the application. In particular, "EIND" is not
	   saved/restored in function or interrupt service routine
	   prologue/epilogue.

       o   For indirect calls to functions and computed goto, the linker
	   generates stubs. Stubs are jump pads sometimes also called
	   trampolines. Thus, the indirect call/jump jumps to such a stub.
	   The stub contains a direct jump to the desired address.

       o   Linker relaxation must be turned on so that the linker will
	   generate the stubs correctly an all situaltion. See the compiler
	   option "-mrelax" and the linler option "--relax".  There are corner
	   cases where the linker is supposed to generate stubs but aborts
	   without relaxation and without a helpful error message.

       o   The default linker script is arranged for code with "EIND = 0".  If
	   code is supposed to work for a setup with "EIND != 0", a custom
	   linker script has to be used in order to place the sections whose
	   name start with ".trampolines" into the segment where "EIND" points
	   to.

       o   The startup code from libgcc never sets "EIND".  Notice that
	   startup code is a blend of code from libgcc and AVR-LibC.  For the
	   impact of AVR-LibC on "EIND", see the AVR-LibC user manual
	   ("http://nongnu.org/avr-libc/user-manual/").

       o   It is legitimate for user-specific startup code to set up "EIND"
	   early, for example by means of initialization code located in
	   section ".init3". Such code runs prior to general startup code that
	   initializes RAM and calls constructors, but after the bit of
	   startup code from AVR-LibC that sets "EIND" to the segment where
	   the vector table is located.

		   #include <avr/io.h>

		   static void
		   __attribute__((section(".init3"),naked,used,no_instrument_function))
		   init3_set_eind (void)
		   {
		     __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
				     "out %i0,r24" :: "n" (&EIND) : "r24","memory");
		   }

	   The "__trampolines_start" symbol is defined in the linker script.

       o   Stubs are generated automatically by the linker if the following
	   two conditions are met:

	   -<The address of a label is taken by means of the "gs" modifier>
	       (short for generate stubs) like so:

		       LDI r24, lo8(gs(<func>))
		       LDI r25, hi8(gs(<func>))

	   -<The final location of that label is in a code segment>
	       outside the segment where the stubs are located.

       o   The compiler emits such "gs" modifiers for code labels in the
	   following situations:

	   -<Taking address of a function or code label.>
	   -<Computed goto.>
	   -<If prologue-save function is used, see -mcall-prologues>
	       command-line option.

	   -<Switch/case dispatch tables. If you do not want such dispatch>
	       tables you can specify the -fno-jump-tables command-line
	       option.

	   -<C and C++ constructors/destructors called during
	   startup/shutdown.>
	   -<If the tools hit a "gs()" modifier explained above.>
       o   Jumping to non-symbolic addresses like so is not supported:

		   int main (void)
		   {
		       /* Call function at word address 0x2 */
		       return ((int(*)(void)) 0x2)();
		   }

	   Instead, a stub has to be set up, i.e. the function has to be
	   called through a symbol ("func_4" in the example):

		   int main (void)
		   {
		       extern int func_4 (void);

		       /* Call function at byte address 0x4 */
		       return func_4();
		   }

	   and the application be linked with "-Wl,--defsym,func_4=0x4".
	   Alternatively, "func_4" can be defined in the linker script.

       Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special Function
       Registers

       Some AVR devices support memories larger than the 64@tie{}KiB range
       that can be accessed with 16-bit pointers.  To access memory locations
       outside this 64@tie{}KiB range, the contentent of a "RAMP" register is
       used as high part of the address: The "X", "Y", "Z" address register is
       concatenated with the "RAMPX", "RAMPY", "RAMPZ" special function
       register, respectively, to get a wide address. Similarly, "RAMPD" is
       used together with direct addressing.

       o   The startup code initializes the "RAMP" special function registers
	   with zero.

       o   If a AVR Named Address Spaces,named address space other than
	   generic or "__flash" is used, then "RAMPZ" is set as needed before
	   the operation.

       o   If the device supports RAM larger than 64@tie{KiB} and the compiler
	   needs to change "RAMPZ" to accomplish an operation, "RAMPZ" is
	   reset to zero after the operation.

       o   If the device comes with a specific "RAMP" register, the ISR
	   prologue/epilogue saves/restores that SFR and initializes it with
	   zero in case the ISR code might (implicitly) use it.

       o   RAM larger than 64@tie{KiB} is not supported by GCC for AVR
	   targets.  If you use inline assembler to read from locations
	   outside the 16-bit address range and change one of the "RAMP"
	   registers, you must reset it to zero after the access.

       AVR Built-in Macros

       GCC defines several built-in macros so that the user code can test for
       the presence or absence of features.  Almost any of the following
       built-in macros are deduced from device capabilities and thus triggered
       by the "-mmcu=" command-line option.

       For even more AVR-specific built-in macros see AVR Named Address Spaces
       and AVR Built-in Functions.

       "__AVR_ARCH__"
	   Build-in macro that resolves to a decimal number that identifies
	   the architecture and depends on the "-mmcu=mcu" option.  Possible
	   values are:

	   2, 25, 3, 31, 35, 4, 5, 51, 6, 102, 104, 105, 106, 107

	   for mcu="avr2", "avr25", "avr3", "avr31", "avr35", "avr4", "avr5",
	   "avr51", "avr6", "avrxmega2", "avrxmega4", "avrxmega5",
	   "avrxmega6", "avrxmega7", respectively.  If mcu specifies a device,
	   this built-in macro is set accordingly. For example, with
	   "-mmcu=atmega8" the macro will be defined to 4.

       "__AVR_Device__"
	   Setting "-mmcu=device" defines this built-in macro which reflects
	   the device's name. For example, "-mmcu=atmega8" defines the built-
	   in macro "__AVR_ATmega8__", "-mmcu=attiny261a" defines
	   "__AVR_ATtiny261A__", etc.

	   The built-in macros' names follow the scheme "__AVR_Device__" where
	   Device is the device name as from the AVR user manual. The
	   difference between Device in the built-in macro and device in
	   "-mmcu=device" is that the latter is always lowercase.

	   If device is not a device but only a core architecture like
	   "avr51", this macro will not be defined.

       "__AVR_XMEGA__"
	   The device / architecture belongs to the XMEGA family of devices.

       "__AVR_HAVE_ELPM__"
	   The device has the the "ELPM" instruction.

       "__AVR_HAVE_ELPMX__"
	   The device has the "ELPM Rn,Z" and "ELPM Rn,Z+" instructions.

       "__AVR_HAVE_MOVW__"
	   The device has the "MOVW" instruction to perform 16-bit register-
	   register moves.

       "__AVR_HAVE_LPMX__"
	   The device has the "LPM Rn,Z" and "LPM Rn,Z+" instructions.

       "__AVR_HAVE_MUL__"
	   The device has a hardware multiplier.

       "__AVR_HAVE_JMP_CALL__"
	   The device has the "JMP" and "CALL" instructions.  This is the case
	   for devices with at least 16@tie{}KiB of program memory.

       "__AVR_HAVE_EIJMP_EICALL__"
       "__AVR_3_BYTE_PC__"
	   The device has the "EIJMP" and "EICALL" instructions.  This is the
	   case for devices with more than 128@tie{}KiB of program memory.
	   This also means that the program counter (PC) is 3@tie{}bytes wide.

       "__AVR_2_BYTE_PC__"
	   The program counter (PC) is 2@tie{}bytes wide. This is the case for
	   devices with up to 128@tie{}KiB of program memory.

       "__AVR_HAVE_8BIT_SP__"
       "__AVR_HAVE_16BIT_SP__"
	   The stack pointer (SP) register is treated as 8-bit respectively
	   16-bit register by the compiler.  The definition of these macros is
	   affected by "-mtiny-stack".

       "__AVR_HAVE_SPH__"
       "__AVR_SP8__"
	   The device has the SPH (high part of stack pointer) special
	   function register or has an 8-bit stack pointer, respectively.  The
	   definition of these macros is affected by "-mmcu=" and in the cases
	   of "-mmcu=avr2" and "-mmcu=avr25" also by "-msp8".

       "__AVR_HAVE_RAMPD__"
       "__AVR_HAVE_RAMPX__"
       "__AVR_HAVE_RAMPY__"
       "__AVR_HAVE_RAMPZ__"
	   The device has the "RAMPD", "RAMPX", "RAMPY", "RAMPZ" special
	   function register, respectively.

       "__NO_INTERRUPTS__"
	   This macro reflects the "-mno-interrupts" command line option.

       "__AVR_ERRATA_SKIP__"
       "__AVR_ERRATA_SKIP_JMP_CALL__"
	   Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit
	   instructions because of a hardware erratum.	Skip instructions are
	   "SBRS", "SBRC", "SBIS", "SBIC" and "CPSE".  The second macro is
	   only defined if "__AVR_HAVE_JMP_CALL__" is also set.

       "__AVR_SFR_OFFSET__=offset"
	   Instructions that can address I/O special function registers
	   directly like "IN", "OUT", "SBI", etc. may use a different address
	   as if addressed by an instruction to access RAM like "LD" or "STS".
	   This offset depends on the device architecture and has to be
	   subtracted from the RAM address in order to get the respective
	   I/O@tie{}address.

       "__WITH_AVRLIBC__"
	   The compiler is configured to be used together with AVR-Libc.  See
	   the "--with-avrlibc" configure option.

   Blackfin Options
       -mcpu=cpu[-sirevision]
	   Specifies the name of the target Blackfin processor.	 Currently,
	   cpu can be one of bf512, bf514, bf516, bf518, bf522, bf523, bf524,
	   bf525, bf526, bf527, bf531, bf532, bf533, bf534, bf536, bf537,
	   bf538, bf539, bf542, bf544, bf547, bf548, bf549, bf542m, bf544m,
	   bf547m, bf548m, bf549m, bf561, bf592.

	   The optional sirevision specifies the silicon revision of the
	   target Blackfin processor.  Any workarounds available for the
	   targeted silicon revision are enabled.  If sirevision is none, no
	   workarounds are enabled.  If sirevision is any, all workarounds for
	   the targeted processor are enabled.	The "__SILICON_REVISION__"
	   macro is defined to two hexadecimal digits representing the major
	   and minor numbers in the silicon revision.  If sirevision is none,
	   the "__SILICON_REVISION__" is not defined.  If sirevision is any,
	   the "__SILICON_REVISION__" is defined to be 0xffff.	If this
	   optional sirevision is not used, GCC assumes the latest known
	   silicon revision of the targeted Blackfin processor.

	   GCC defines a preprocessor macro for the specified cpu.  For the
	   bfin-elf toolchain, this option causes the hardware BSP provided by
	   libgloss to be linked in if -msim is not given.

	   Without this option, bf532 is used as the processor by default.

	   Note that support for bf561 is incomplete.  For bf561, only the
	   preprocessor macro is defined.

       -msim
	   Specifies that the program will be run on the simulator.  This
	   causes the simulator BSP provided by libgloss to be linked in.
	   This option has effect only for bfin-elf toolchain.	Certain other
	   options, such as -mid-shared-library and -mfdpic, imply -msim.

       -momit-leaf-frame-pointer
	   Don't keep the frame pointer in a register for leaf functions.
	   This avoids the instructions to save, set up and restore frame
	   pointers and makes an extra register available in leaf functions.
	   The option -fomit-frame-pointer removes the frame pointer for all
	   functions, which might make debugging harder.

       -mspecld-anomaly
	   When enabled, the compiler ensures that the generated code does not
	   contain speculative loads after jump instructions. If this option
	   is used, "__WORKAROUND_SPECULATIVE_LOADS" is defined.

       -mno-specld-anomaly
	   Don't generate extra code to prevent speculative loads from
	   occurring.

       -mcsync-anomaly
	   When enabled, the compiler ensures that the generated code does not
	   contain CSYNC or SSYNC instructions too soon after conditional
	   branches.  If this option is used, "__WORKAROUND_SPECULATIVE_SYNCS"
	   is defined.

       -mno-csync-anomaly
	   Don't generate extra code to prevent CSYNC or SSYNC instructions
	   from occurring too soon after a conditional branch.

       -mlow-64k
	   When enabled, the compiler is free to take advantage of the
	   knowledge that the entire program fits into the low 64k of memory.

       -mno-low-64k
	   Assume that the program is arbitrarily large.  This is the default.

       -mstack-check-l1
	   Do stack checking using information placed into L1 scratchpad
	   memory by the uClinux kernel.

       -mid-shared-library
	   Generate code that supports shared libraries via the library ID
	   method.  This allows for execute in place and shared libraries in
	   an environment without virtual memory management.  This option
	   implies -fPIC.  With a bfin-elf target, this option implies -msim.

       -mno-id-shared-library
	   Generate code that doesn't assume ID-based shared libraries are
	   being used.	This is the default.

       -mleaf-id-shared-library
	   Generate code that supports shared libraries via the library ID
	   method, but assumes that this library or executable won't link
	   against any other ID shared libraries.  That allows the compiler to
	   use faster code for jumps and calls.

       -mno-leaf-id-shared-library
	   Do not assume that the code being compiled won't link against any
	   ID shared libraries.	 Slower code is generated for jump and call
	   insns.

       -mshared-library-id=n
	   Specifies the identification number of the ID-based shared library
	   being compiled.  Specifying a value of 0 generates more compact
	   code; specifying other values forces the allocation of that number
	   to the current library but is no more space- or time-efficient than
	   omitting this option.

       -msep-data
	   Generate code that allows the data segment to be located in a
	   different area of memory from the text segment.  This allows for
	   execute in place in an environment without virtual memory
	   management by eliminating relocations against the text section.

       -mno-sep-data
	   Generate code that assumes that the data segment follows the text
	   segment.  This is the default.

       -mlong-calls
       -mno-long-calls
	   Tells the compiler to perform function calls by first loading the
	   address of the function into a register and then performing a
	   subroutine call on this register.  This switch is needed if the
	   target function lies outside of the 24-bit addressing range of the
	   offset-based version of subroutine call instruction.

	   This feature is not enabled by default.  Specifying -mno-long-calls
	   restores the default behavior.  Note these switches have no effect
	   on how the compiler generates code to handle function calls via
	   function pointers.

       -mfast-fp
	   Link with the fast floating-point library. This library relaxes
	   some of the IEEE floating-point standard's rules for checking
	   inputs against Not-a-Number (NAN), in the interest of performance.

       -minline-plt
	   Enable inlining of PLT entries in function calls to functions that
	   are not known to bind locally.  It has no effect without -mfdpic.

       -mmulticore
	   Build a standalone application for multicore Blackfin processors.
	   This option causes proper start files and link scripts supporting
	   multicore to be used, and defines the macro "__BFIN_MULTICORE".  It
	   can only be used with -mcpu=bf561[-sirevision].

	   This option can be used with -mcorea or -mcoreb, which selects the
	   one-application-per-core programming model.	Without -mcorea or
	   -mcoreb, the single-application/dual-core programming model is
	   used. In this model, the main function of Core B should be named as
	   "coreb_main".

	   If this option is not used, the single-core application programming
	   model is used.

       -mcorea
	   Build a standalone application for Core A of BF561 when using the
	   one-application-per-core programming model. Proper start files and
	   link scripts are used to support Core A, and the macro
	   "__BFIN_COREA" is defined.  This option can only be used in
	   conjunction with -mmulticore.

       -mcoreb
	   Build a standalone application for Core B of BF561 when using the
	   one-application-per-core programming model. Proper start files and
	   link scripts are used to support Core B, and the macro
	   "__BFIN_COREB" is defined. When this option is used, "coreb_main"
	   should be used instead of "main".  This option can only be used in
	   conjunction with -mmulticore.

       -msdram
	   Build a standalone application for SDRAM. Proper start files and
	   link scripts are used to put the application into SDRAM, and the
	   macro "__BFIN_SDRAM" is defined.  The loader should initialize
	   SDRAM before loading the application.

       -micplb
	   Assume that ICPLBs are enabled at run time.	This has an effect on
	   certain anomaly workarounds.	 For Linux targets, the default is to
	   assume ICPLBs are enabled; for standalone applications the default
	   is off.

   C6X Options
       -march=name
	   This specifies the name of the target architecture.	GCC uses this
	   name to determine what kind of instructions it can emit when
	   generating assembly code.  Permissible names are: c62x, c64x,
	   c64x+, c67x, c67x+, c674x.

       -mbig-endian
	   Generate code for a big-endian target.

       -mlittle-endian
	   Generate code for a little-endian target.  This is the default.

       -msim
	   Choose startup files and linker script suitable for the simulator.

       -msdata=default
	   Put small global and static data in the .neardata section, which is
	   pointed to by register "B14".  Put small uninitialized global and
	   static data in the .bss section, which is adjacent to the .neardata
	   section.  Put small read-only data into the .rodata section.	 The
	   corresponding sections used for large pieces of data are .fardata,
	   .far and .const.

       -msdata=all
	   Put all data, not just small objects, into the sections reserved
	   for small data, and use addressing relative to the "B14" register
	   to access them.

       -msdata=none
	   Make no use of the sections reserved for small data, and use
	   absolute addresses to access all data.  Put all initialized global
	   and static data in the .fardata section, and all uninitialized data
	   in the .far section.	 Put all constant data into the .const
	   section.

   CRIS Options
       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
	   Generate code for the specified architecture.  The choices for
	   architecture-type are v3, v8 and v10 for respectively ETRAX 4,
	   ETRAX 100, and ETRAX 100 LX.	 Default is v0 except for cris-axis-
	   linux-gnu, where the default is v10.

       -mtune=architecture-type
	   Tune to architecture-type everything applicable about the generated
	   code, except for the ABI and the set of available instructions.
	   The choices for architecture-type are the same as for
	   -march=architecture-type.

       -mmax-stack-frame=n
	   Warn when the stack frame of a function exceeds n bytes.

       -metrax4
       -metrax100
	   The options -metrax4 and -metrax100 are synonyms for -march=v3 and
	   -march=v8 respectively.

       -mmul-bug-workaround
       -mno-mul-bug-workaround
	   Work around a bug in the "muls" and "mulu" instructions for CPU
	   models where it applies.  This option is active by default.

       -mpdebug
	   Enable CRIS-specific verbose debug-related information in the
	   assembly code.  This option also has the effect of turning off the
	   #NO_APP formatted-code indicator to the assembler at the beginning
	   of the assembly file.

       -mcc-init
	   Do not use condition-code results from previous instruction; always
	   emit compare and test instructions before use of condition codes.

       -mno-side-effects
	   Do not emit instructions with side effects in addressing modes
	   other than post-increment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
	   These options (no- options) arrange (eliminate arrangements) for
	   the stack frame, individual data and constants to be aligned for
	   the maximum single data access size for the chosen CPU model.  The
	   default is to arrange for 32-bit alignment.	ABI details such as
	   structure layout are not affected by these options.

       -m32-bit
       -m16-bit
       -m8-bit
	   Similar to the stack- data- and const-align options above, these
	   options arrange for stack frame, writable data and constants to all
	   be 32-bit, 16-bit or 8-bit aligned.	The default is 32-bit
	   alignment.

       -mno-prologue-epilogue
       -mprologue-epilogue
	   With -mno-prologue-epilogue, the normal function prologue and
	   epilogue which set up the stack frame are omitted and no return
	   instructions or return sequences are generated in the code.	Use
	   this option only together with visual inspection of the compiled
	   code: no warnings or errors are generated when call-saved registers
	   must be saved, or storage for local variables needs to be
	   allocated.

       -mno-gotplt
       -mgotplt
	   With -fpic and -fPIC, don't generate (do generate) instruction
	   sequences that load addresses for functions from the PLT part of
	   the GOT rather than (traditional on other architectures) calls to
	   the PLT.  The default is -mgotplt.

       -melf
	   Legacy no-op option only recognized with the cris-axis-elf and
	   cris-axis-linux-gnu targets.

       -mlinux
	   Legacy no-op option only recognized with the cris-axis-linux-gnu
	   target.

       -sim
	   This option, recognized for the cris-axis-elf, arranges to link
	   with input-output functions from a simulator library.  Code,
	   initialized data and zero-initialized data are allocated
	   consecutively.

       -sim2
	   Like -sim, but pass linker options to locate initialized data at
	   0x40000000 and zero-initialized data at 0x80000000.

   CR16 Options
       These options are defined specifically for the CR16 ports.

       -mmac
	   Enable the use of multiply-accumulate instructions. Disabled by
	   default.

       -mcr16cplus
       -mcr16c
	   Generate code for CR16C or CR16C+ architecture. CR16C+ architecture
	   is default.

       -msim
	   Links the library libsim.a which is in compatible with simulator.
	   Applicable to ELF compiler only.

       -mint32
	   Choose integer type as 32-bit wide.

       -mbit-ops
	   Generates "sbit"/"cbit" instructions for bit manipulations.

       -mdata-model=model
	   Choose a data model. The choices for model are near, far or medium.
	   medium is default.  However, far is not valid with -mcr16c, as the
	   CR16C architecture does not support the far data model.

   Darwin Options
       These options are defined for all architectures running the Darwin
       operating system.

       FSF GCC on Darwin does not create "fat" object files; it creates an
       object file for the single architecture that GCC was built to target.
       Apple's GCC on Darwin does create "fat" files if multiple -arch options
       are used; it does so by running the compiler or linker multiple times
       and joining the results together with lipo.

       The subtype of the file created (like ppc7400 or ppc970 or i686) is
       determined by the flags that specify the ISA that GCC is targeting,
       like -mcpu or -march.  The -force_cpusubtype_ALL option can be used to
       override this.

       The Darwin tools vary in their behavior when presented with an ISA
       mismatch.  The assembler, as, only permits instructions to be used that
       are valid for the subtype of the file it is generating, so you cannot
       put 64-bit instructions in a ppc750 object file.	 The linker for shared
       libraries, /usr/bin/libtool, fails and prints an error if asked to
       create a shared library with a less restrictive subtype than its input
       files (for instance, trying to put a ppc970 object file in a ppc7400
       library).  The linker for executables, ld, quietly gives the executable
       the most restrictive subtype of any of its input files.

       -Fdir
	   Add the framework directory dir to the head of the list of
	   directories to be searched for header files.	 These directories are
	   interleaved with those specified by -I options and are scanned in a
	   left-to-right order.

	   A framework directory is a directory with frameworks in it.	A
	   framework is a directory with a Headers and/or PrivateHeaders
	   directory contained directly in it that ends in .framework.	The
	   name of a framework is the name of this directory excluding the
	   .framework.	Headers associated with the framework are found in one
	   of those two directories, with Headers being searched first.	 A
	   subframework is a framework directory that is in a framework's
	   Frameworks directory.  Includes of subframework headers can only
	   appear in a header of a framework that contains the subframework,
	   or in a sibling subframework header.	 Two subframeworks are
	   siblings if they occur in the same framework.  A subframework
	   should not have the same name as a framework; a warning is issued
	   if this is violated.	 Currently a subframework cannot have
	   subframeworks; in the future, the mechanism may be extended to
	   support this.  The standard frameworks can be found in
	   /System/Library/Frameworks and /Library/Frameworks.	An example
	   include looks like "#include <Framework/header.h>", where Framework
	   denotes the name of the framework and header.h is found in the
	   PrivateHeaders or Headers directory.

       -iframeworkdir
	   Like -F except the directory is a treated as a system directory.
	   The main difference between this -iframework and -F is that with
	   -iframework the compiler does not warn about constructs contained
	   within header files found via dir.  This option is valid only for
	   the C family of languages.

       -gused
	   Emit debugging information for symbols that are used.  For stabs
	   debugging format, this enables -feliminate-unused-debug-symbols.
	   This is by default ON.

       -gfull
	   Emit debugging information for all symbols and types.

       -mmacosx-version-min=version
	   The earliest version of MacOS X that this executable will run on is
	   version.  Typical values of version include 10.1, 10.2, and 10.3.9.

	   If the compiler was built to use the system's headers by default,
	   then the default for this option is the system version on which the
	   compiler is running, otherwise the default is to make choices that
	   are compatible with as many systems and code bases as possible.

       -mkernel
	   Enable kernel development mode.  The -mkernel option sets -static,
	   -fno-common, -fno-use-cxa-atexit, -fno-exceptions,
	   -fno-non-call-exceptions, -fapple-kext, -fno-weak and -fno-rtti
	   where applicable.  This mode also sets -mno-altivec, -msoft-float,
	   -fno-builtin and -mlong-branch for PowerPC targets.

       -mone-byte-bool
	   Override the defaults for bool so that sizeof(bool)==1.  By default
	   sizeof(bool) is 4 when compiling for Darwin/PowerPC and 1 when
	   compiling for Darwin/x86, so this option has no effect on x86.

	   Warning: The -mone-byte-bool switch causes GCC to generate code
	   that is not binary compatible with code generated without that
	   switch.  Using this switch may require recompiling all other
	   modules in a program, including system libraries.  Use this switch
	   to conform to a non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
	   Generate code suitable for fast turnaround development, such as to
	   allow GDB to dynamically load ".o" files into already-running
	   programs.  -findirect-data and -ffix-and-continue are provided for
	   backwards compatibility.

       -all_load
	   Loads all members of static archive libraries.  See man ld(1) for
	   more information.

       -arch_errors_fatal
	   Cause the errors having to do with files that have the wrong
	   architecture to be fatal.

       -bind_at_load
	   Causes the output file to be marked such that the dynamic linker
	   will bind all undefined references when the file is loaded or
	   launched.

       -bundle
	   Produce a Mach-o bundle format file.	 See man ld(1) for more
	   information.

       -bundle_loader executable
	   This option specifies the executable that will load the build
	   output file being linked.  See man ld(1) for more information.

       -dynamiclib
	   When passed this option, GCC produces a dynamic library instead of
	   an executable when linking, using the Darwin libtool command.

       -force_cpusubtype_ALL
	   This causes GCC's output file to have the ALL subtype, instead of
	   one controlled by the -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
	   These options are passed to the Darwin linker.  The Darwin linker
	   man page describes them in detail.

   DEC Alpha Options
       These -m options are defined for the DEC Alpha implementations:

       -mno-soft-float
       -msoft-float
	   Use (do not use) the hardware floating-point instructions for
	   floating-point operations.  When -msoft-float is specified,
	   functions in libgcc.a are used to perform floating-point
	   operations.	Unless they are replaced by routines that emulate the
	   floating-point operations, or compiled in such a way as to call
	   such emulations routines, these routines issue floating-point
	   operations.	 If you are compiling for an Alpha without floating-
	   point operations, you must ensure that the library is built so as
	   not to call them.

	   Note that Alpha implementations without floating-point operations
	   are required to have floating-point registers.

       -mfp-reg
       -mno-fp-regs
	   Generate code that uses (does not use) the floating-point register
	   set.	 -mno-fp-regs implies -msoft-float.  If the floating-point
	   register set is not used, floating-point operands are passed in
	   integer registers as if they were integers and floating-point
	   results are passed in $0 instead of $f0.  This is a non-standard
	   calling sequence, so any function with a floating-point argument or
	   return value called by code compiled with -mno-fp-regs must also be
	   compiled with that option.

	   A typical use of this option is building a kernel that does not
	   use, and hence need not save and restore, any floating-point
	   registers.

       -mieee
	   The Alpha architecture implements floating-point hardware optimized
	   for maximum performance.  It is mostly compliant with the IEEE
	   floating-point standard.  However, for full compliance, software
	   assistance is required.  This option generates code fully IEEE-
	   compliant code except that the inexact-flag is not maintained (see
	   below).  If this option is turned on, the preprocessor macro
	   "_IEEE_FP" is defined during compilation.  The resulting code is
	   less efficient but is able to correctly support denormalized
	   numbers and exceptional IEEE values such as not-a-number and
	   plus/minus infinity.	 Other Alpha compilers call this option
	   -ieee_with_no_inexact.

       -mieee-with-inexact
	   This is like -mieee except the generated code also maintains the
	   IEEE inexact-flag.  Turning on this option causes the generated
	   code to implement fully-compliant IEEE math.	 In addition to
	   "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor macro.
	   On some Alpha implementations the resulting code may execute
	   significantly slower than the code generated by default.  Since
	   there is very little code that depends on the inexact-flag, you
	   should normally not specify this option.  Other Alpha compilers
	   call this option -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
	   This option controls what floating-point related traps are enabled.
	   Other Alpha compilers call this option -fptm trap-mode.  The trap
	   mode can be set to one of four values:

	   n   This is the default (normal) setting.  The only traps that are
	       enabled are the ones that cannot be disabled in software (e.g.,
	       division by zero trap).

	   u   In addition to the traps enabled by n, underflow traps are
	       enabled as well.

	   su  Like u, but the instructions are marked to be safe for software
	       completion (see Alpha architecture manual for details).

	   sui Like su, but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
	   Selects the IEEE rounding mode.  Other Alpha compilers call this
	   option -fprm rounding-mode.	The rounding-mode can be one of:

	   n   Normal IEEE rounding mode.  Floating-point numbers are rounded
	       towards the nearest machine number or towards the even machine
	       number in case of a tie.

	   m   Round towards minus infinity.

	   c   Chopped rounding mode.  Floating-point numbers are rounded
	       towards zero.

	   d   Dynamic rounding mode.  A field in the floating-point control
	       register (fpcr, see Alpha architecture reference manual)
	       controls the rounding mode in effect.  The C library
	       initializes this register for rounding towards plus infinity.
	       Thus, unless your program modifies the fpcr, d corresponds to
	       round towards plus infinity.

       -mtrap-precision=trap-precision
	   In the Alpha architecture, floating-point traps are imprecise.
	   This means without software assistance it is impossible to recover
	   from a floating trap and program execution normally needs to be
	   terminated.	GCC can generate code that can assist operating system
	   trap handlers in determining the exact location that caused a
	   floating-point trap.	 Depending on the requirements of an
	   application, different levels of precisions can be selected:

	   p   Program precision.  This option is the default and means a trap
	       handler can only identify which program caused a floating-point
	       exception.

	   f   Function precision.  The trap handler can determine the
	       function that caused a floating-point exception.

	   i   Instruction precision.  The trap handler can determine the
	       exact instruction that caused a floating-point exception.

	   Other Alpha compilers provide the equivalent options called
	   -scope_safe and -resumption_safe.

       -mieee-conformant
	   This option marks the generated code as IEEE conformant.  You must
	   not use this option unless you also specify -mtrap-precision=i and
	   either -mfp-trap-mode=su or -mfp-trap-mode=sui.  Its only effect is
	   to emit the line .eflag 48 in the function prologue of the
	   generated assembly file.

       -mbuild-constants
	   Normally GCC examines a 32- or 64-bit integer constant to see if it
	   can construct it from smaller constants in two or three
	   instructions.  If it cannot, it outputs the constant as a literal
	   and generates code to load it from the data segment at run time.

	   Use this option to require GCC to construct all integer constants
	   using code, even if it takes more instructions (the maximum is
	   six).

	   You typically use this option to build a shared library dynamic
	   loader.  Itself a shared library, it must relocate itself in memory
	   before it can find the variables and constants in its own data
	   segment.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
	   Indicate whether GCC should generate code to use the optional BWX,
	   CIX, FIX and MAX instruction sets.  The default is to use the
	   instruction sets supported by the CPU type specified via -mcpu=
	   option or that of the CPU on which GCC was built if none is
	   specified.

       -mfloat-vax
       -mfloat-ieee
	   Generate code that uses (does not use) VAX F and G floating-point
	   arithmetic instead of IEEE single and double precision.

       -mexplicit-relocs
       -mno-explicit-relocs
	   Older Alpha assemblers provided no way to generate symbol
	   relocations except via assembler macros.  Use of these macros does
	   not allow optimal instruction scheduling.  GNU binutils as of
	   version 2.12 supports a new syntax that allows the compiler to
	   explicitly mark which relocations should apply to which
	   instructions.  This option is mostly useful for debugging, as GCC
	   detects the capabilities of the assembler when it is built and sets
	   the default accordingly.

       -msmall-data
       -mlarge-data
	   When -mexplicit-relocs is in effect, static data is accessed via
	   gp-relative relocations.  When -msmall-data is used, objects 8
	   bytes long or smaller are placed in a small data area (the ".sdata"
	   and ".sbss" sections) and are accessed via 16-bit relocations off
	   of the $gp register.	 This limits the size of the small data area
	   to 64KB, but allows the variables to be directly accessed via a
	   single instruction.

	   The default is -mlarge-data.	 With this option the data area is
	   limited to just below 2GB.  Programs that require more than 2GB of
	   data must use "malloc" or "mmap" to allocate the data in the heap
	   instead of in the program's data segment.

	   When generating code for shared libraries, -fpic implies
	   -msmall-data and -fPIC implies -mlarge-data.

       -msmall-text
       -mlarge-text
	   When -msmall-text is used, the compiler assumes that the code of
	   the entire program (or shared library) fits in 4MB, and is thus
	   reachable with a branch instruction.	 When -msmall-data is used,
	   the compiler can assume that all local symbols share the same $gp
	   value, and thus reduce the number of instructions required for a
	   function call from 4 to 1.

	   The default is -mlarge-text.

       -mcpu=cpu_type
	   Set the instruction set and instruction scheduling parameters for
	   machine type cpu_type.  You can specify either the EV style name or
	   the corresponding chip number.  GCC supports scheduling parameters
	   for the EV4, EV5 and EV6 family of processors and chooses the
	   default values for the instruction set from the processor you
	   specify.  If you do not specify a processor type, GCC defaults to
	   the processor on which the compiler was built.

	   Supported values for cpu_type are

	   ev4
	   ev45
	   21064
	       Schedules as an EV4 and has no instruction set extensions.

	   ev5
	   21164
	       Schedules as an EV5 and has no instruction set extensions.

	   ev56
	   21164a
	       Schedules as an EV5 and supports the BWX extension.

	   pca56
	   21164pc
	   21164PC
	       Schedules as an EV5 and supports the BWX and MAX extensions.

	   ev6
	   21264
	       Schedules as an EV6 and supports the BWX, FIX, and MAX
	       extensions.

	   ev67
	   21264a
	       Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX
	       extensions.

	   Native toolchains also support the value native, which selects the
	   best architecture option for the host processor.  -mcpu=native has
	   no effect if GCC does not recognize the processor.

       -mtune=cpu_type
	   Set only the instruction scheduling parameters for machine type
	   cpu_type.  The instruction set is not changed.

	   Native toolchains also support the value native, which selects the
	   best architecture option for the host processor.  -mtune=native has
	   no effect if GCC does not recognize the processor.

       -mmemory-latency=time
	   Sets the latency the scheduler should assume for typical memory
	   references as seen by the application.  This number is highly
	   dependent on the memory access patterns used by the application and
	   the size of the external cache on the machine.

	   Valid options for time are

	   number
	       A decimal number representing clock cycles.

	   L1
	   L2
	   L3
	   main
	       The compiler contains estimates of the number of clock cycles
	       for "typical" EV4 & EV5 hardware for the Level 1, 2 & 3 caches
	       (also called Dcache, Scache, and Bcache), as well as to main
	       memory.	Note that L3 is only valid for EV5.

   FR30 Options
       These options are defined specifically for the FR30 port.

       -msmall-model
	   Use the small address space model.  This can produce smaller code,
	   but it does assume that all symbolic values and addresses fit into
	   a 20-bit range.

       -mno-lsim
	   Assume that runtime support has been provided and so there is no
	   need to include the simulator library (libsim.a) on the linker
	   command line.

   FRV Options
       -mgpr-32
	   Only use the first 32 general-purpose registers.

       -mgpr-64
	   Use all 64 general-purpose registers.

       -mfpr-32
	   Use only the first 32 floating-point registers.

       -mfpr-64
	   Use all 64 floating-point registers.

       -mhard-float
	   Use hardware instructions for floating-point operations.

       -msoft-float
	   Use library routines for floating-point operations.

       -malloc-cc
	   Dynamically allocate condition code registers.

       -mfixed-cc
	   Do not try to dynamically allocate condition code registers, only
	   use "icc0" and "fcc0".

       -mdword
	   Change ABI to use double word insns.

       -mno-dword
	   Do not use double word instructions.

       -mdouble
	   Use floating-point double instructions.

       -mno-double
	   Do not use floating-point double instructions.

       -mmedia
	   Use media instructions.

       -mno-media
	   Do not use media instructions.

       -mmuladd
	   Use multiply and add/subtract instructions.

       -mno-muladd
	   Do not use multiply and add/subtract instructions.

       -mfdpic
	   Select the FDPIC ABI, which uses function descriptors to represent
	   pointers to functions.  Without any PIC/PIE-related options, it
	   implies -fPIE.  With -fpic or -fpie, it assumes GOT entries and
	   small data are within a 12-bit range from the GOT base address;
	   with -fPIC or -fPIE, GOT offsets are computed with 32 bits.	With a
	   bfin-elf target, this option implies -msim.

       -minline-plt
	   Enable inlining of PLT entries in function calls to functions that
	   are not known to bind locally.  It has no effect without -mfdpic.
	   It's enabled by default if optimizing for speed and compiling for
	   shared libraries (i.e., -fPIC or -fpic), or when an optimization
	   option such as -O3 or above is present in the command line.

       -mTLS
	   Assume a large TLS segment when generating thread-local code.

       -mtls
	   Do not assume a large TLS segment when generating thread-local
	   code.

       -mgprel-ro
	   Enable the use of "GPREL" relocations in the FDPIC ABI for data
	   that is known to be in read-only sections.  It's enabled by
	   default, except for -fpic or -fpie: even though it may help make
	   the global offset table smaller, it trades 1 instruction for 4.
	   With -fPIC or -fPIE, it trades 3 instructions for 4, one of which
	   may be shared by multiple symbols, and it avoids the need for a GOT
	   entry for the referenced symbol, so it's more likely to be a win.
	   If it is not, -mno-gprel-ro can be used to disable it.

       -multilib-library-pic
	   Link with the (library, not FD) pic libraries.  It's implied by
	   -mlibrary-pic, as well as by -fPIC and -fpic without -mfdpic.  You
	   should never have to use it explicitly.

       -mlinked-fp
	   Follow the EABI requirement of always creating a frame pointer
	   whenever a stack frame is allocated.	 This option is enabled by
	   default and can be disabled with -mno-linked-fp.

       -mlong-calls
	   Use indirect addressing to call functions outside the current
	   compilation unit.  This allows the functions to be placed anywhere
	   within the 32-bit address space.

       -malign-labels
	   Try to align labels to an 8-byte boundary by inserting NOPs into
	   the previous packet.	 This option only has an effect when VLIW
	   packing is enabled.	It doesn't create new packets; it merely adds
	   NOPs to existing ones.

       -mlibrary-pic
	   Generate position-independent EABI code.

       -macc-4
	   Use only the first four media accumulator registers.

       -macc-8
	   Use all eight media accumulator registers.

       -mpack
	   Pack VLIW instructions.

       -mno-pack
	   Do not pack VLIW instructions.

       -mno-eflags
	   Do not mark ABI switches in e_flags.

       -mcond-move
	   Enable the use of conditional-move instructions (default).

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mno-cond-move
	   Disable the use of conditional-move instructions.

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mscc
	   Enable the use of conditional set instructions (default).

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mno-scc
	   Disable the use of conditional set instructions.

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mcond-exec
	   Enable the use of conditional execution (default).

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mno-cond-exec
	   Disable the use of conditional execution.

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mvliw-branch
	   Run a pass to pack branches into VLIW instructions (default).

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mno-vliw-branch
	   Do not run a pass to pack branches into VLIW instructions.

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mmulti-cond-exec
	   Enable optimization of "&&" and "||" in conditional execution
	   (default).

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mno-multi-cond-exec
	   Disable optimization of "&&" and "||" in conditional execution.

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mnested-cond-exec
	   Enable nested conditional execution optimizations (default).

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -mno-nested-cond-exec
	   Disable nested conditional execution optimizations.

	   This switch is mainly for debugging the compiler and will likely be
	   removed in a future version.

       -moptimize-membar
	   This switch removes redundant "membar" instructions from the
	   compiler-generated code.  It is enabled by default.

       -mno-optimize-membar
	   This switch disables the automatic removal of redundant "membar"
	   instructions from the generated code.

       -mtomcat-stats
	   Cause gas to print out tomcat statistics.

       -mcpu=cpu
	   Select the processor type for which to generate code.  Possible
	   values are frv, fr550, tomcat, fr500, fr450, fr405, fr400, fr300
	   and simple.

   GNU/Linux Options
       These -m options are defined for GNU/Linux targets:

       -mglibc
	   Use the GNU C library.  This is the default except on
	   *-*-linux-*uclibc* and *-*-linux-*android* targets.

       -muclibc
	   Use uClibc C library.  This is the default on *-*-linux-*uclibc*
	   targets.

       -mbionic
	   Use Bionic C library.  This is the default on *-*-linux-*android*
	   targets.

       -mandroid
	   Compile code compatible with Android platform.  This is the default
	   on *-*-linux-*android* targets.

	   When compiling, this option enables -mbionic, -fPIC,
	   -fno-exceptions and -fno-rtti by default.  When linking, this
	   option makes the GCC driver pass Android-specific options to the
	   linker.  Finally, this option causes the preprocessor macro
	   "__ANDROID__" to be defined.

       -tno-android-cc
	   Disable compilation effects of -mandroid, i.e., do not enable
	   -mbionic, -fPIC, -fno-exceptions and -fno-rtti by default.

       -tno-android-ld
	   Disable linking effects of -mandroid, i.e., pass standard Linux
	   linking options to the linker.

   H8/300 Options
       These -m options are defined for the H8/300 implementations:

       -mrelax
	   Shorten some address references at link time, when possible; uses
	   the linker option -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8S.

       -mn Generate code for the H8S and H8/300H in the normal mode.  This
	   switch must be used either with -mh or -ms.

       -ms2600
	   Generate code for the H8S/2600.  This switch must be used with -ms.

       -mexr
	   Extended registers are stored on stack before execution of function
	   with monitor attribute. Default option is -mexr.  This option is
	   valid only for H8S targets.

       -mno-exr
	   Extended registers are not stored on stack before execution of
	   function with monitor attribute. Default option is -mno-exr.	 This
	   option is valid only for H8S targets.

       -mint32
	   Make "int" data 32 bits by default.

       -malign-300
	   On the H8/300H and H8S, use the same alignment rules as for the
	   H8/300.  The default for the H8/300H and H8S is to align longs and
	   floats on 4-byte boundaries.	 -malign-300 causes them to be aligned
	   on 2-byte boundaries.  This option has no effect on the H8/300.

   HPPA Options
       These -m options are defined for the HPPA family of computers:

       -march=architecture-type
	   Generate code for the specified architecture.  The choices for
	   architecture-type are 1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for
	   PA 2.0 processors.  Refer to /usr/lib/sched.models on an HP-UX
	   system to determine the proper architecture option for your
	   machine.  Code compiled for lower numbered architectures runs on
	   higher numbered architectures, but not the other way around.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
	   Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively.

       -mbig-switch
	   Generate code suitable for big switch tables.  Use this option only
	   if the assembler/linker complain about out-of-range branches within
	   a switch table.

       -mjump-in-delay
	   Fill delay slots of function calls with unconditional jump
	   instructions by modifying the return pointer for the function call
	   to be the target of the conditional jump.

       -mdisable-fpregs
	   Prevent floating-point registers from being used in any manner.
	   This is necessary for compiling kernels that perform lazy context
	   switching of floating-point registers.  If you use this option and
	   attempt to perform floating-point operations, the compiler aborts.

       -mdisable-indexing
	   Prevent the compiler from using indexing address modes.  This
	   avoids some rather obscure problems when compiling MIG generated
	   code under MACH.

       -mno-space-regs
	   Generate code that assumes the target has no space registers.  This
	   allows GCC to generate faster indirect calls and use unscaled index
	   address modes.

	   Such code is suitable for level 0 PA systems and kernels.

       -mfast-indirect-calls
	   Generate code that assumes calls never cross space boundaries.
	   This allows GCC to emit code that performs faster indirect calls.

	   This option does not work in the presence of shared libraries or
	   nested functions.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.
	   A fixed register is one that the register allocator cannot use.
	   This is useful when compiling kernel code.  A register range is
	   specified as two registers separated by a dash.  Multiple register
	   ranges can be specified separated by a comma.

       -mlong-load-store
	   Generate 3-instruction load and store sequences as sometimes
	   required by the HP-UX 10 linker.  This is equivalent to the +k
	   option to the HP compilers.

       -mportable-runtime
	   Use the portable calling conventions proposed by HP for ELF
	   systems.

       -mgas
	   Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
	   Schedule code according to the constraints for the machine type
	   cpu-type.  The choices for cpu-type are 700 7100, 7100LC, 7200,
	   7300 and 8000.  Refer to /usr/lib/sched.models on an HP-UX system
	   to determine the proper scheduling option for your machine.	The
	   default scheduling is 8000.

       -mlinker-opt
	   Enable the optimization pass in the HP-UX linker.  Note this makes
	   symbolic debugging impossible.  It also triggers a bug in the HP-UX
	   8 and HP-UX 9 linkers in which they give bogus error messages when
	   linking some programs.

       -msoft-float
	   Generate output containing library calls for floating point.
	   Warning: the requisite libraries are not available for all HPPA
	   targets.  Normally the facilities of the machine's usual C compiler
	   are used, but this cannot be done directly in cross-compilation.
	   You must make your own arrangements to provide suitable library
	   functions for cross-compilation.

	   -msoft-float changes the calling convention in the output file;
	   therefore, it is only useful if you compile all of a program with
	   this option.	 In particular, you need to compile libgcc.a, the
	   library that comes with GCC, with -msoft-float in order for this to
	   work.

       -msio
	   Generate the predefine, "_SIO", for server IO.  The default is
	   -mwsio.  This generates the predefines, "__hp9000s700",
	   "__hp9000s700__" and "_WSIO", for workstation IO.  These options
	   are available under HP-UX and HI-UX.

       -mgnu-ld
	   Use options specific to GNU ld.  This passes -shared to ld when
	   building a shared library.  It is the default when GCC is
	   configured, explicitly or implicitly, with the GNU linker.  This
	   option does not affect which ld is called; it only changes what
	   parameters are passed to that ld.  The ld that is called is
	   determined by the --with-ld configure option, GCC's program search
	   path, and finally by the user's PATH.  The linker used by GCC can
	   be printed using which `gcc -print-prog-name=ld`.  This option is
	   only available on the 64-bit HP-UX GCC, i.e. configured with
	   hppa*64*-*-hpux*.

       -mhp-ld
	   Use options specific to HP ld.  This passes -b to ld when building
	   a shared library and passes +Accept TypeMismatch to ld on all
	   links.  It is the default when GCC is configured, explicitly or
	   implicitly, with the HP linker.  This option does not affect which
	   ld is called; it only changes what parameters are passed to that
	   ld.	The ld that is called is determined by the --with-ld configure
	   option, GCC's program search path, and finally by the user's PATH.
	   The linker used by GCC can be printed using which `gcc
	   -print-prog-name=ld`.  This option is only available on the 64-bit
	   HP-UX GCC, i.e. configured with hppa*64*-*-hpux*.

       -mlong-calls
	   Generate code that uses long call sequences.	 This ensures that a
	   call is always able to reach linker generated stubs.	 The default
	   is to generate long calls only when the distance from the call site
	   to the beginning of the function or translation unit, as the case
	   may be, exceeds a predefined limit set by the branch type being
	   used.  The limits for normal calls are 7,600,000 and 240,000 bytes,
	   respectively for the PA 2.0 and PA 1.X architectures.  Sibcalls are
	   always limited at 240,000 bytes.

	   Distances are measured from the beginning of functions when using
	   the -ffunction-sections option, or when using the -mgas and
	   -mno-portable-runtime options together under HP-UX with the SOM
	   linker.

	   It is normally not desirable to use this option as it degrades
	   performance.	 However, it may be useful in large applications,
	   particularly when partial linking is used to build the application.

	   The types of long calls used depends on the capabilities of the
	   assembler and linker, and the type of code being generated.	The
	   impact on systems that support long absolute calls, and long pic
	   symbol-difference or pc-relative calls should be relatively small.
	   However, an indirect call is used on 32-bit ELF systems in pic code
	   and it is quite long.

       -munix=unix-std
	   Generate compiler predefines and select a startfile for the
	   specified UNIX standard.  The choices for unix-std are 93, 95 and
	   98.	93 is supported on all HP-UX versions.	95 is available on HP-
	   UX 10.10 and later.	98 is available on HP-UX 11.11 and later.  The
	   default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though to
	   11.00, and 98 for HP-UX 11.11 and later.

	   -munix=93 provides the same predefines as GCC 3.3 and 3.4.
	   -munix=95 provides additional predefines for "XOPEN_UNIX" and
	   "_XOPEN_SOURCE_EXTENDED", and the startfile unix95.o.  -munix=98
	   provides additional predefines for "_XOPEN_UNIX",
	   "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and
	   "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o.

	   It is important to note that this option changes the interfaces for
	   various library routines.  It also affects the operational behavior
	   of the C library.  Thus, extreme care is needed in using this
	   option.

	   Library code that is intended to operate with more than one UNIX
	   standard must test, set and restore the variable
	   __xpg4_extended_mask as appropriate.	 Most GNU software doesn't
	   provide this capability.

       -nolibdld
	   Suppress the generation of link options to search libdld.sl when
	   the -static option is specified on HP-UX 10 and later.

       -static
	   The HP-UX implementation of setlocale in libc has a dependency on
	   libdld.sl.  There isn't an archive version of libdld.sl.  Thus,
	   when the -static option is specified, special link options are
	   needed to resolve this dependency.

	   On HP-UX 10 and later, the GCC driver adds the necessary options to
	   link with libdld.sl when the -static option is specified.  This
	   causes the resulting binary to be dynamic.  On the 64-bit port, the
	   linkers generate dynamic binaries by default in any case.  The
	   -nolibdld option can be used to prevent the GCC driver from adding
	   these link options.

       -threads
	   Add support for multithreading with the dce thread library under
	   HP-UX.  This option sets flags for both the preprocessor and
	   linker.

   Intel 386 and AMD x86-64 Options
       These -m options are defined for the i386 and x86-64 family of
       computers:

       -march=cpu-type
	   Generate instructions for the machine type cpu-type.	 In contrast
	   to -mtune=cpu-type, which merely tunes the generated code for the
	   specified cpu-type, -march=cpu-type allows GCC to generate code
	   that may not run at all on processors other than the one indicated.
	   Specifying -march=cpu-type implies -mtune=cpu-type.

	   The choices for cpu-type are:

	   native
	       This selects the CPU to generate code for at compilation time
	       by determining the processor type of the compiling machine.
	       Using -march=native enables all instruction subsets supported
	       by the local machine (hence the result might not run on
	       different machines).  Using -mtune=native produces code
	       optimized for the local machine under the constraints of the
	       selected instruction set.

	   i386
	       Original Intel i386 CPU.

	   i486
	       Intel i486 CPU.	(No scheduling is implemented for this chip.)

	   i586
	   pentium
	       Intel Pentium CPU with no MMX support.

	   pentium-mmx
	       Intel Pentium MMX CPU, based on Pentium core with MMX
	       instruction set support.

	   pentiumpro
	       Intel Pentium Pro CPU.

	   i686
	       When used with -march, the Pentium Pro instruction set is used,
	       so the code runs on all i686 family chips.  When used with
	       -mtune, it has the same meaning as generic.

	   pentium2
	       Intel Pentium II CPU, based on Pentium Pro core with MMX
	       instruction set support.

	   pentium3
	   pentium3m
	       Intel Pentium III CPU, based on Pentium Pro core with MMX and
	       SSE instruction set support.

	   pentium-m
	       Intel Pentium M; low-power version of Intel Pentium III CPU
	       with MMX, SSE and SSE2 instruction set support.	Used by
	       Centrino notebooks.

	   pentium4
	   pentium4m
	       Intel Pentium 4 CPU with MMX, SSE and SSE2 instruction set
	       support.

	   prescott
	       Improved version of Intel Pentium 4 CPU with MMX, SSE, SSE2 and
	       SSE3 instruction set support.

	   nocona
	       Improved version of Intel Pentium 4 CPU with 64-bit extensions,
	       MMX, SSE, SSE2 and SSE3 instruction set support.

	   core2
	       Intel Core 2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3
	       and SSSE3 instruction set support.

	   corei7
	       Intel Core i7 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3,
	       SSSE3, SSE4.1 and SSE4.2 instruction set support.

	   corei7-avx
	       Intel Core i7 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3,
	       SSSE3, SSE4.1, SSE4.2, AVX, AES and PCLMUL instruction set
	       support.

	   core-avx-i
	       Intel Core CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3,
	       SSSE3, SSE4.1, SSE4.2, AVX, AES, PCLMUL, FSGSBASE, RDRND and
	       F16C instruction set support.

	   core-avx2
	       Intel Core CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2,
	       SSE3, SSSE3, SSE4.1, SSE4.2, AVX, AVX2, AES, PCLMUL, FSGSBASE,
	       RDRND, FMA, BMI, BMI2 and F16C instruction set support.

	   atom
	       Intel Atom CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2,
	       SSE3 and SSSE3 instruction set support.

	   k6  AMD K6 CPU with MMX instruction set support.

	   k6-2
	   k6-3
	       Improved versions of AMD K6 CPU with MMX and 3DNow! instruction
	       set support.

	   athlon
	   athlon-tbird
	       AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow! and SSE
	       prefetch instructions support.

	   athlon-4
	   athlon-xp
	   athlon-mp
	       Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow! and
	       full SSE instruction set support.

	   k8
	   opteron
	   athlon64
	   athlon-fx
	       Processors based on the AMD K8 core with x86-64 instruction set
	       support, including the AMD Opteron, Athlon 64, and Athlon 64 FX
	       processors.  (This supersets MMX, SSE, SSE2, 3DNow!, enhanced
	       3DNow! and 64-bit instruction set extensions.)

	   k8-sse3
	   opteron-sse3
	   athlon64-sse3
	       Improved versions of AMD K8 cores with SSE3 instruction set
	       support.

	   amdfam10
	   barcelona
	       CPUs based on AMD Family 10h cores with x86-64 instruction set
	       support.	 (This supersets MMX, SSE, SSE2, SSE3, SSE4A, 3DNow!,
	       enhanced 3DNow!, ABM and 64-bit instruction set extensions.)

	   bdver1
	       CPUs based on AMD Family 15h cores with x86-64 instruction set
	       support.	 (This supersets FMA4, AVX, XOP, LWP, AES, PCL_MUL,
	       CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM
	       and 64-bit instruction set extensions.)

	   bdver2
	       AMD Family 15h core based CPUs with x86-64 instruction set
	       support.	 (This supersets BMI, TBM, F16C, FMA, AVX, XOP, LWP,
	       AES, PCL_MUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1,
	       SSE4.2, ABM and 64-bit instruction set extensions.)

	   bdver3
	       AMD Family 15h core based CPUs with x86-64 instruction set
	       support.	 (This supersets BMI, TBM, F16C, FMA, AVX, XOP, LWP,
	       AES, PCL_MUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1,
	       SSE4.2, ABM and 64-bit instruction set extensions.

	   btver1
	       CPUs based on AMD Family 14h cores with x86-64 instruction set
	       support.	 (This supersets MMX, SSE, SSE2, SSE3, SSSE3, SSE4A,
	       CX16, ABM and 64-bit instruction set extensions.)

	   btver2
	       CPUs based on AMD Family 16h cores with x86-64 instruction set
	       support. This includes MOVBE, F16C, BMI, AVX, PCL_MUL, AES,
	       SSE4.2, SSE4.1, CX16, ABM, SSE4A, SSSE3, SSE3, SSE2, SSE, MMX
	       and 64-bit instruction set extensions.

	   winchip-c6
	       IDT WinChip C6 CPU, dealt in same way as i486 with additional
	       MMX instruction set support.

	   winchip2
	       IDT WinChip 2 CPU, dealt in same way as i486 with additional
	       MMX and 3DNow!  instruction set support.

	   c3  VIA C3 CPU with MMX and 3DNow! instruction set support.	(No
	       scheduling is implemented for this chip.)

	   c3-2
	       VIA C3-2 (Nehemiah/C5XL) CPU with MMX and SSE instruction set
	       support.	 (No scheduling is implemented for this chip.)

	   geode
	       AMD Geode embedded processor with MMX and 3DNow! instruction
	       set support.

       -mtune=cpu-type
	   Tune to cpu-type everything applicable about the generated code,
	   except for the ABI and the set of available instructions.  While
	   picking a specific cpu-type schedules things appropriately for that
	   particular chip, the compiler does not generate any code that
	   cannot run on the default machine type unless you use a -march=cpu-
	   type option.	 For example, if GCC is configured for
	   i686-pc-linux-gnu then -mtune=pentium4 generates code that is tuned
	   for Pentium 4 but still runs on i686 machines.

	   The choices for cpu-type are the same as for -march.	 In addition,
	   -mtune supports an extra choice for cpu-type:

	   generic
	       Produce code optimized for the most common IA32/AMD64/EM64T
	       processors.  If you know the CPU on which your code will run,
	       then you should use the corresponding -mtune or -march option
	       instead of -mtune=generic.  But, if you do not know exactly
	       what CPU users of your application will have, then you should
	       use this option.

	       As new processors are deployed in the marketplace, the behavior
	       of this option will change.  Therefore, if you upgrade to a
	       newer version of GCC, code generation controlled by this option
	       will change to reflect the processors that are most common at
	       the time that version of GCC is released.

	       There is no -march=generic option because -march indicates the
	       instruction set the compiler can use, and there is no generic
	       instruction set applicable to all processors.  In contrast,
	       -mtune indicates the processor (or, in this case, collection of
	       processors) for which the code is optimized.

       -mcpu=cpu-type
	   A deprecated synonym for -mtune.

       -mfpmath=unit
	   Generate floating-point arithmetic for selected unit unit.  The
	   choices for unit are:

	   387 Use the standard 387 floating-point coprocessor present on the
	       majority of chips and emulated otherwise.  Code compiled with
	       this option runs almost everywhere.  The temporary results are
	       computed in 80-bit precision instead of the precision specified
	       by the type, resulting in slightly different results compared
	       to most of other chips.	See -ffloat-store for more detailed
	       description.

	       This is the default choice for i386 compiler.

	   sse Use scalar floating-point instructions present in the SSE
	       instruction set.	 This instruction set is supported by Pentium
	       III and newer chips, and in the AMD line by Athlon-4, Athlon XP
	       and Athlon MP chips.  The earlier version of the SSE
	       instruction set supports only single-precision arithmetic, thus
	       the double and extended-precision arithmetic are still done
	       using 387.  A later version, present only in Pentium 4 and AMD
	       x86-64 chips, supports double-precision arithmetic too.

	       For the i386 compiler, you must use -march=cpu-type, -msse or
	       -msse2 switches to enable SSE extensions and make this option
	       effective.  For the x86-64 compiler, these extensions are
	       enabled by default.

	       The resulting code should be considerably faster in the
	       majority of cases and avoid the numerical instability problems
	       of 387 code, but may break some existing code that expects
	       temporaries to be 80 bits.

	       This is the default choice for the x86-64 compiler.

	   sse,387
	   sse+387
	   both
	       Attempt to utilize both instruction sets at once.  This
	       effectively doubles the amount of available registers, and on
	       chips with separate execution units for 387 and SSE the
	       execution resources too.	 Use this option with care, as it is
	       still experimental, because the GCC register allocator does not
	       model separate functional units well, resulting in unstable
	       performance.

       -masm=dialect
	   Output assembly instructions using selected dialect.	 Supported
	   choices are intel or att (the default).  Darwin does not support
	   intel.

       -mieee-fp
       -mno-ieee-fp
	   Control whether or not the compiler uses IEEE floating-point
	   comparisons.	 These correctly handle the case where the result of a
	   comparison is unordered.

       -msoft-float
	   Generate output containing library calls for floating point.

	   Warning: the requisite libraries are not part of GCC.  Normally the
	   facilities of the machine's usual C compiler are used, but this
	   can't be done directly in cross-compilation.	 You must make your
	   own arrangements to provide suitable library functions for cross-
	   compilation.

	   On machines where a function returns floating-point results in the
	   80387 register stack, some floating-point opcodes may be emitted
	   even if -msoft-float is used.

       -mno-fp-ret-in-387
	   Do not use the FPU registers for return values of functions.

	   The usual calling convention has functions return values of types
	   "float" and "double" in an FPU register, even if there is no FPU.
	   The idea is that the operating system should emulate an FPU.

	   The option -mno-fp-ret-in-387 causes such values to be returned in
	   ordinary CPU registers instead.

       -mno-fancy-math-387
	   Some 387 emulators do not support the "sin", "cos" and "sqrt"
	   instructions for the 387.  Specify this option to avoid generating
	   those instructions.	This option is the default on FreeBSD, OpenBSD
	   and NetBSD.	This option is overridden when -march indicates that
	   the target CPU always has an FPU and so the instruction does not
	   need emulation.  These instructions are not generated unless you
	   also use the -funsafe-math-optimizations switch.

       -malign-double
       -mno-align-double
	   Control whether GCC aligns "double", "long double", and "long long"
	   variables on a two-word boundary or a one-word boundary.  Aligning
	   "double" variables on a two-word boundary produces code that runs
	   somewhat faster on a Pentium at the expense of more memory.

	   On x86-64, -malign-double is enabled by default.

	   Warning: if you use the -malign-double switch, structures
	   containing the above types are aligned differently than the
	   published application binary interface specifications for the 386
	   and are not binary compatible with structures in code compiled
	   without that switch.

       -m96bit-long-double
       -m128bit-long-double
	   These switches control the size of "long double" type.  The i386
	   application binary interface specifies the size to be 96 bits, so
	   -m96bit-long-double is the default in 32-bit mode.

	   Modern architectures (Pentium and newer) prefer "long double" to be
	   aligned to an 8- or 16-byte boundary.  In arrays or structures
	   conforming to the ABI, this is not possible.	 So specifying
	   -m128bit-long-double aligns "long double" to a 16-byte boundary by
	   padding the "long double" with an additional 32-bit zero.

	   In the x86-64 compiler, -m128bit-long-double is the default choice
	   as its ABI specifies that "long double" is aligned on 16-byte
	   boundary.

	   Notice that neither of these options enable any extra precision
	   over the x87 standard of 80 bits for a "long double".

	   Warning: if you override the default value for your target ABI,
	   this changes the size of structures and arrays containing "long
	   double" variables, as well as modifying the function calling
	   convention for functions taking "long double".  Hence they are not
	   binary-compatible with code compiled without that switch.

       -mlong-double-64
       -mlong-double-80
	   These switches control the size of "long double" type. A size of 64
	   bits makes the "long double" type equivalent to the "double" type.
	   This is the default for Bionic C library.

	   Warning: if you override the default value for your target ABI,
	   this changes the size of structures and arrays containing "long
	   double" variables, as well as modifying the function calling
	   convention for functions taking "long double".  Hence they are not
	   binary-compatible with code compiled without that switch.

       -mlarge-data-threshold=threshold
	   When -mcmodel=medium is specified, data objects larger than
	   threshold are placed in the large data section.  This value must be
	   the same across all objects linked into the binary, and defaults to
	   65535.

       -mrtd
	   Use a different function-calling convention, in which functions
	   that take a fixed number of arguments return with the "ret num"
	   instruction, which pops their arguments while returning.  This
	   saves one instruction in the caller since there is no need to pop
	   the arguments there.

	   You can specify that an individual function is called with this
	   calling sequence with the function attribute stdcall.  You can also
	   override the -mrtd option by using the function attribute cdecl.

	   Warning: this calling convention is incompatible with the one
	   normally used on Unix, so you cannot use it if you need to call
	   libraries compiled with the Unix compiler.

	   Also, you must provide function prototypes for all functions that
	   take variable numbers of arguments (including "printf"); otherwise
	   incorrect code is generated for calls to those functions.

	   In addition, seriously incorrect code results if you call a
	   function with too many arguments.  (Normally, extra arguments are
	   harmlessly ignored.)

       -mregparm=num
	   Control how many registers are used to pass integer arguments.  By
	   default, no registers are used to pass arguments, and at most 3
	   registers can be used.  You can control this behavior for a
	   specific function by using the function attribute regparm.

	   Warning: if you use this switch, and num is nonzero, then you must
	   build all modules with the same value, including any libraries.
	   This includes the system libraries and startup modules.

       -msseregparm
	   Use SSE register passing conventions for float and double arguments
	   and return values.  You can control this behavior for a specific
	   function by using the function attribute sseregparm.

	   Warning: if you use this switch then you must build all modules
	   with the same value, including any libraries.  This includes the
	   system libraries and startup modules.

       -mvect8-ret-in-mem
	   Return 8-byte vectors in memory instead of MMX registers.  This is
	   the default on Solaris@tie{}8 and 9 and VxWorks to match the ABI of
	   the Sun Studio compilers until version 12.  Later compiler versions
	   (starting with Studio 12 Update@tie{}1) follow the ABI used by
	   other x86 targets, which is the default on Solaris@tie{}10 and
	   later.  Only use this option if you need to remain compatible with
	   existing code produced by those previous compiler versions or older
	   versions of GCC.

       -mpc32
       -mpc64
       -mpc80
	   Set 80387 floating-point precision to 32, 64 or 80 bits.  When
	   -mpc32 is specified, the significands of results of floating-point
	   operations are rounded to 24 bits (single precision); -mpc64 rounds
	   the significands of results of floating-point operations to 53 bits
	   (double precision) and -mpc80 rounds the significands of results of
	   floating-point operations to 64 bits (extended double precision),
	   which is the default.  When this option is used, floating-point
	   operations in higher precisions are not available to the programmer
	   without setting the FPU control word explicitly.

	   Setting the rounding of floating-point operations to less than the
	   default 80 bits can speed some programs by 2% or more.  Note that
	   some mathematical libraries assume that extended-precision (80-bit)
	   floating-point operations are enabled by default; routines in such
	   libraries could suffer significant loss of accuracy, typically
	   through so-called "catastrophic cancellation", when this option is
	   used to set the precision to less than extended precision.

       -mstackrealign
	   Realign the stack at entry.	On the Intel x86, the -mstackrealign
	   option generates an alternate prologue and epilogue that realigns
	   the run-time stack if necessary.  This supports mixing legacy codes
	   that keep 4-byte stack alignment with modern codes that keep
	   16-byte stack alignment for SSE compatibility.  See also the
	   attribute "force_align_arg_pointer", applicable to individual
	   functions.

       -mpreferred-stack-boundary=num
	   Attempt to keep the stack boundary aligned to a 2 raised to num
	   byte boundary.  If -mpreferred-stack-boundary is not specified, the
	   default is 4 (16 bytes or 128 bits).

	   Warning: When generating code for the x86-64 architecture with SSE
	   extensions disabled, -mpreferred-stack-boundary=3 can be used to
	   keep the stack boundary aligned to 8 byte boundary.	Since x86-64
	   ABI require 16 byte stack alignment, this is ABI incompatible and
	   intended to be used in controlled environment where stack space is
	   important limitation.  This option will lead to wrong code when
	   functions compiled with 16 byte stack alignment (such as functions
	   from a standard library) are called with misaligned stack.  In this
	   case, SSE instructions may lead to misaligned memory access traps.
	   In addition, variable arguments will be handled incorrectly for 16
	   byte aligned objects (including x87 long double and __int128),
	   leading to wrong results.  You must build all modules with
	   -mpreferred-stack-boundary=3, including any libraries.  This
	   includes the system libraries and startup modules.

       -mincoming-stack-boundary=num
	   Assume the incoming stack is aligned to a 2 raised to num byte
	   boundary.  If -mincoming-stack-boundary is not specified, the one
	   specified by -mpreferred-stack-boundary is used.

	   On Pentium and Pentium Pro, "double" and "long double" values
	   should be aligned to an 8-byte boundary (see -malign-double) or
	   suffer significant run time performance penalties.  On Pentium III,
	   the Streaming SIMD Extension (SSE) data type "__m128" may not work
	   properly if it is not 16-byte aligned.

	   To ensure proper alignment of this values on the stack, the stack
	   boundary must be as aligned as that required by any value stored on
	   the stack.  Further, every function must be generated such that it
	   keeps the stack aligned.  Thus calling a function compiled with a
	   higher preferred stack boundary from a function compiled with a
	   lower preferred stack boundary most likely misaligns the stack.  It
	   is recommended that libraries that use callbacks always use the
	   default setting.

	   This extra alignment does consume extra stack space, and generally
	   increases code size.	 Code that is sensitive to stack space usage,
	   such as embedded systems and operating system kernels, may want to
	   reduce the preferred alignment to -mpreferred-stack-boundary=2.

       -mmmx
       -mno-mmx
       -msse
       -mno-sse
       -msse2
       -mno-sse2
       -msse3
       -mno-sse3
       -mssse3
       -mno-ssse3
       -msse4.1
       -mno-sse4.1
       -msse4.2
       -mno-sse4.2
       -msse4
       -mno-sse4
       -mavx
       -mno-avx
       -mavx2
       -mno-avx2
       -maes
       -mno-aes
       -mpclmul
       -mno-pclmul
       -mfsgsbase
       -mno-fsgsbase
       -mrdrnd
       -mno-rdrnd
       -mf16c
       -mno-f16c
       -mfma
       -mno-fma
       -msse4a
       -mno-sse4a
       -mfma4
       -mno-fma4
       -mxop
       -mno-xop
       -mlwp
       -mno-lwp
       -m3dnow
       -mno-3dnow
       -mpopcnt
       -mno-popcnt
       -mabm
       -mno-abm
       -mbmi
       -mbmi2
       -mno-bmi
       -mno-bmi2
       -mlzcnt
       -mno-lzcnt
       -mrtm
       -mtbm
       -mno-tbm
	   These switches enable or disable the use of instructions in the
	   MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, AVX, AVX2, AES, PCLMUL,
	   FSGSBASE, RDRND, F16C, FMA, SSE4A, FMA4, XOP, LWP, ABM, BMI, BMI2,
	   LZCNT, RTM or 3DNow!	 extended instruction sets.  These extensions
	   are also available as built-in functions: see X86 Built-in
	   Functions, for details of the functions enabled and disabled by
	   these switches.

	   To generate SSE/SSE2 instructions automatically from floating-point
	   code (as opposed to 387 instructions), see -mfpmath=sse.

	   GCC depresses SSEx instructions when -mavx is used. Instead, it
	   generates new AVX instructions or AVX equivalence for all SSEx
	   instructions when needed.

	   These options enable GCC to use these extended instructions in
	   generated code, even without -mfpmath=sse.  Applications that
	   perform run-time CPU detection must compile separate files for each
	   supported architecture, using the appropriate flags.	 In
	   particular, the file containing the CPU detection code should be
	   compiled without these options.

       -mcld
	   This option instructs GCC to emit a "cld" instruction in the
	   prologue of functions that use string instructions.	String
	   instructions depend on the DF flag to select between autoincrement
	   or autodecrement mode.  While the ABI specifies the DF flag to be
	   cleared on function entry, some operating systems violate this
	   specification by not clearing the DF flag in their exception
	   dispatchers.	 The exception handler can be invoked with the DF flag
	   set, which leads to wrong direction mode when string instructions
	   are used.  This option can be enabled by default on 32-bit x86
	   targets by configuring GCC with the --enable-cld configure option.
	   Generation of "cld" instructions can be suppressed with the
	   -mno-cld compiler option in this case.

       -mvzeroupper
	   This option instructs GCC to emit a "vzeroupper" instruction before
	   a transfer of control flow out of the function to minimize the AVX
	   to SSE transition penalty as well as remove unnecessary "zeroupper"
	   intrinsics.

       -mprefer-avx128
	   This option instructs GCC to use 128-bit AVX instructions instead
	   of 256-bit AVX instructions in the auto-vectorizer.

       -mcx16
	   This option enables GCC to generate "CMPXCHG16B" instructions.
	   "CMPXCHG16B" allows for atomic operations on 128-bit double
	   quadword (or oword) data types.  This is useful for high-resolution
	   counters that can be updated by multiple processors (or cores).
	   This instruction is generated as part of atomic built-in functions:
	   see __sync Builtins or __atomic Builtins for details.

       -msahf
	   This option enables generation of "SAHF" instructions in 64-bit
	   code.  Early Intel Pentium 4 CPUs with Intel 64 support, prior to
	   the introduction of Pentium 4 G1 step in December 2005, lacked the
	   "LAHF" and "SAHF" instructions which were supported by AMD64.
	   These are load and store instructions, respectively, for certain
	   status flags.  In 64-bit mode, the "SAHF" instruction is used to
	   optimize "fmod", "drem", and "remainder" built-in functions; see
	   Other Builtins for details.

       -mmovbe
	   This option enables use of the "movbe" instruction to implement
	   "__builtin_bswap32" and "__builtin_bswap64".

       -mcrc32
	   This option enables built-in functions "__builtin_ia32_crc32qi",
	   "__builtin_ia32_crc32hi", "__builtin_ia32_crc32si" and
	   "__builtin_ia32_crc32di" to generate the "crc32" machine
	   instruction.

       -mrecip
	   This option enables use of "RCPSS" and "RSQRTSS" instructions (and
	   their vectorized variants "RCPPS" and "RSQRTPS") with an additional
	   Newton-Raphson step to increase precision instead of "DIVSS" and
	   "SQRTSS" (and their vectorized variants) for single-precision
	   floating-point arguments.  These instructions are generated only
	   when -funsafe-math-optimizations is enabled together with
	   -finite-math-only and -fno-trapping-math.  Note that while the
	   throughput of the sequence is higher than the throughput of the
	   non-reciprocal instruction, the precision of the sequence can be
	   decreased by up to 2 ulp (i.e. the inverse of 1.0 equals
	   0.99999994).

	   Note that GCC implements "1.0f/sqrtf(x)" in terms of "RSQRTSS" (or
	   "RSQRTPS") already with -ffast-math (or the above option
	   combination), and doesn't need -mrecip.

	   Also note that GCC emits the above sequence with additional Newton-
	   Raphson step for vectorized single-float division and vectorized
	   "sqrtf(x)" already with -ffast-math (or the above option
	   combination), and doesn't need -mrecip.

       -mrecip=opt
	   This option controls which reciprocal estimate instructions may be
	   used.  opt is a comma-separated list of options, which may be
	   preceded by a ! to invert the option:

	   all Enable all estimate instructions.

	   default
	       Enable the default instructions, equivalent to -mrecip.

	   none
	       Disable all estimate instructions, equivalent to -mno-recip.

	   div Enable the approximation for scalar division.

	   vec-div
	       Enable the approximation for vectorized division.

	   sqrt
	       Enable the approximation for scalar square root.

	   vec-sqrt
	       Enable the approximation for vectorized square root.

	   So, for example, -mrecip=all,!sqrt enables all of the reciprocal
	   approximations, except for square root.

       -mveclibabi=type
	   Specifies the ABI type to use for vectorizing intrinsics using an
	   external library.  Supported values for type are svml for the Intel
	   short vector math library and acml for the AMD math core library.
	   To use this option, both -ftree-vectorize and
	   -funsafe-math-optimizations have to be enabled, and an SVML or ACML
	   ABI-compatible library must be specified at link time.

	   GCC currently emits calls to "vmldExp2", "vmldLn2", "vmldLog102",
	   "vmldLog102", "vmldPow2", "vmldTanh2", "vmldTan2", "vmldAtan2",
	   "vmldAtanh2", "vmldCbrt2", "vmldSinh2", "vmldSin2", "vmldAsinh2",
	   "vmldAsin2", "vmldCosh2", "vmldCos2", "vmldAcosh2", "vmldAcos2",
	   "vmlsExp4", "vmlsLn4", "vmlsLog104", "vmlsLog104", "vmlsPow4",
	   "vmlsTanh4", "vmlsTan4", "vmlsAtan4", "vmlsAtanh4", "vmlsCbrt4",
	   "vmlsSinh4", "vmlsSin4", "vmlsAsinh4", "vmlsAsin4", "vmlsCosh4",
	   "vmlsCos4", "vmlsAcosh4" and "vmlsAcos4" for corresponding function
	   type when -mveclibabi=svml is used, and "__vrd2_sin", "__vrd2_cos",
	   "__vrd2_exp", "__vrd2_log", "__vrd2_log2", "__vrd2_log10",
	   "__vrs4_sinf", "__vrs4_cosf", "__vrs4_expf", "__vrs4_logf",
	   "__vrs4_log2f", "__vrs4_log10f" and "__vrs4_powf" for the
	   corresponding function type when -mveclibabi=acml is used.

       -mabi=name
	   Generate code for the specified calling convention.	Permissible
	   values are sysv for the ABI used on GNU/Linux and other systems,
	   and ms for the Microsoft ABI.  The default is to use the Microsoft
	   ABI when targeting Microsoft Windows and the SysV ABI on all other
	   systems.  You can control this behavior for a specific function by
	   using the function attribute ms_abi/sysv_abi.

       -mtls-dialect=type
	   Generate code to access thread-local storage using the gnu or gnu2
	   conventions.	 gnu is the conservative default; gnu2 is more
	   efficient, but it may add compile- and run-time requirements that
	   cannot be satisfied on all systems.

       -mpush-args
       -mno-push-args
	   Use PUSH operations to store outgoing parameters.  This method is
	   shorter and usually equally fast as method using SUB/MOV operations
	   and is enabled by default.  In some cases disabling it may improve
	   performance because of improved scheduling and reduced
	   dependencies.

       -maccumulate-outgoing-args
	   If enabled, the maximum amount of space required for outgoing
	   arguments is computed in the function prologue.  This is faster on
	   most modern CPUs because of reduced dependencies, improved
	   scheduling and reduced stack usage when the preferred stack
	   boundary is not equal to 2.	The drawback is a notable increase in
	   code size.  This switch implies -mno-push-args.

       -mthreads
	   Support thread-safe exception handling on MinGW.  Programs that
	   rely on thread-safe exception handling must compile and link all
	   code with the -mthreads option.  When compiling, -mthreads defines
	   "-D_MT"; when linking, it links in a special thread helper library
	   -lmingwthrd which cleans up per-thread exception-handling data.

       -mno-align-stringops
	   Do not align the destination of inlined string operations.  This
	   switch reduces code size and improves performance in case the
	   destination is already aligned, but GCC doesn't know about it.

       -minline-all-stringops
	   By default GCC inlines string operations only when the destination
	   is known to be aligned to least a 4-byte boundary.  This enables
	   more inlining and increases code size, but may improve performance
	   of code that depends on fast "memcpy", "strlen", and "memset" for
	   short lengths.

       -minline-stringops-dynamically
	   For string operations of unknown size, use run-time checks with
	   inline code for small blocks and a library call for large blocks.

       -mstringop-strategy=alg
	   Override the internal decision heuristic for the particular
	   algorithm to use for inlining string operations.  The allowed
	   values for alg are:

	   rep_byte
	   rep_4byte
	   rep_8byte
	       Expand using i386 "rep" prefix of the specified size.

	   byte_loop
	   loop
	   unrolled_loop
	       Expand into an inline loop.

	   libcall
	       Always use a library call.

       -momit-leaf-frame-pointer
	   Don't keep the frame pointer in a register for leaf functions.
	   This avoids the instructions to save, set up, and restore frame
	   pointers and makes an extra register available in leaf functions.
	   The option -fomit-leaf-frame-pointer removes the frame pointer for
	   leaf functions, which might make debugging harder.

       -mtls-direct-seg-refs
       -mno-tls-direct-seg-refs
	   Controls whether TLS variables may be accessed with offsets from
	   the TLS segment register (%gs for 32-bit, %fs for 64-bit), or
	   whether the thread base pointer must be added.  Whether or not this
	   is valid depends on the operating system, and whether it maps the
	   segment to cover the entire TLS area.

	   For systems that use the GNU C Library, the default is on.

       -msse2avx
       -mno-sse2avx
	   Specify that the assembler should encode SSE instructions with VEX
	   prefix.  The option -mavx turns this on by default.

       -mfentry
       -mno-fentry
	   If profiling is active (-pg), put the profiling counter call before
	   the prologue.  Note: On x86 architectures the attribute
	   "ms_hook_prologue" isn't possible at the moment for -mfentry and
	   -pg.

       -m8bit-idiv
       -mno-8bit-idiv
	   On some processors, like Intel Atom, 8-bit unsigned integer divide
	   is much faster than 32-bit/64-bit integer divide.  This option
	   generates a run-time check.	If both dividend and divisor are
	   within range of 0 to 255, 8-bit unsigned integer divide is used
	   instead of 32-bit/64-bit integer divide.

       -mavx256-split-unaligned-load
       -mavx256-split-unaligned-store
	   Split 32-byte AVX unaligned load and store.

       These -m switches are supported in addition to the above on x86-64
       processors in 64-bit environments.

       -m32
       -m64
       -mx32
	   Generate code for a 32-bit or 64-bit environment.  The -m32 option
	   sets "int", "long", and pointer types to 32 bits, and generates
	   code that runs on any i386 system.

	   The -m64 option sets "int" to 32 bits and "long" and pointer types
	   to 64 bits, and generates code for the x86-64 architecture.	For
	   Darwin only the -m64 option also turns off the -fno-pic and
	   -mdynamic-no-pic options.

	   The -mx32 option sets "int", "long", and pointer types to 32 bits,
	   and generates code for the x86-64 architecture.

       -mno-red-zone
	   Do not use a so-called "red zone" for x86-64 code.  The red zone is
	   mandated by the x86-64 ABI; it is a 128-byte area beyond the
	   location of the stack pointer that is not modified by signal or
	   interrupt handlers and therefore can be used for temporary data
	   without adjusting the stack pointer.	 The flag -mno-red-zone
	   disables this red zone.

       -mcmodel=small
	   Generate code for the small code model: the program and its symbols
	   must be linked in the lower 2 GB of the address space.  Pointers
	   are 64 bits.	 Programs can be statically or dynamically linked.
	   This is the default code model.

       -mcmodel=kernel
	   Generate code for the kernel code model.  The kernel runs in the
	   negative 2 GB of the address space.	This model has to be used for
	   Linux kernel code.

       -mcmodel=medium
	   Generate code for the medium model: the program is linked in the
	   lower 2 GB of the address space.  Small symbols are also placed
	   there.  Symbols with sizes larger than -mlarge-data-threshold are
	   put into large data or BSS sections and can be located above 2GB.
	   Programs can be statically or dynamically linked.

       -mcmodel=large
	   Generate code for the large model.  This model makes no assumptions
	   about addresses and sizes of sections.

       -maddress-mode=long
	   Generate code for long address mode.	 This is only supported for
	   64-bit and x32 environments.	 It is the default address mode for
	   64-bit environments.

       -maddress-mode=short
	   Generate code for short address mode.  This is only supported for
	   32-bit and x32 environments.	 It is the default address mode for
	   32-bit and x32 environments.

   i386 and x86-64 Windows Options
       These additional options are available for Microsoft Windows targets:

       -mconsole
	   This option specifies that a console application is to be
	   generated, by instructing the linker to set the PE header subsystem
	   type required for console applications.  This option is available
	   for Cygwin and MinGW targets and is enabled by default on those
	   targets.

       -mdll
	   This option is available for Cygwin and MinGW targets.  It
	   specifies that a DLL---a dynamic link library---is to be generated,
	   enabling the selection of the required runtime startup object and
	   entry point.

       -mnop-fun-dllimport
	   This option is available for Cygwin and MinGW targets.  It
	   specifies that the "dllimport" attribute should be ignored.

       -mthread
	   This option is available for MinGW targets. It specifies that
	   MinGW-specific thread support is to be used.

       -municode
	   This option is available for MinGW-w64 targets.  It causes the
	   "UNICODE" preprocessor macro to be predefined, and chooses Unicode-
	   capable runtime startup code.

       -mwin32
	   This option is available for Cygwin and MinGW targets.  It
	   specifies that the typical Microsoft Windows predefined macros are
	   to be set in the pre-processor, but does not influence the choice
	   of runtime library/startup code.

       -mwindows
	   This option is available for Cygwin and MinGW targets.  It
	   specifies that a GUI application is to be generated by instructing
	   the linker to set the PE header subsystem type appropriately.

       -fno-set-stack-executable
	   This option is available for MinGW targets. It specifies that the
	   executable flag for the stack used by nested functions isn't set.
	   This is necessary for binaries running in kernel mode of Microsoft
	   Windows, as there the User32 API, which is used to set executable
	   privileges, isn't available.

       -fwritable-relocated-rdata
	   This option is available for MinGW and Cygwin targets.  It
	   specifies that relocated-data in read-only section is put into
	   .data section.  This is a necessary for older runtimes not
	   supporting modification of .rdata sections for pseudo-relocation.

       -mpe-aligned-commons
	   This option is available for Cygwin and MinGW targets.  It
	   specifies that the GNU extension to the PE file format that permits
	   the correct alignment of COMMON variables should be used when
	   generating code.  It is enabled by default if GCC detects that the
	   target assembler found during configuration supports the feature.

       See also under i386 and x86-64 Options for standard options.

   IA-64 Options
       These are the -m options defined for the Intel IA-64 architecture.

       -mbig-endian
	   Generate code for a big-endian target.  This is the default for HP-
	   UX.

       -mlittle-endian
	   Generate code for a little-endian target.  This is the default for
	   AIX5 and GNU/Linux.

       -mgnu-as
       -mno-gnu-as
	   Generate (or don't) code for the GNU assembler.  This is the
	   default.

       -mgnu-ld
       -mno-gnu-ld
	   Generate (or don't) code for the GNU linker.	 This is the default.

       -mno-pic
	   Generate code that does not use a global pointer register.  The
	   result is not position independent code, and violates the IA-64
	   ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
	   Generate (or don't) a stop bit immediately before and after
	   volatile asm statements.

       -mregister-names
       -mno-register-names
	   Generate (or don't) in, loc, and out register names for the stacked
	   registers.  This may make assembler output more readable.

       -mno-sdata
       -msdata
	   Disable (or enable) optimizations that use the small data section.
	   This may be useful for working around optimizer bugs.

       -mconstant-gp
	   Generate code that uses a single constant global pointer value.
	   This is useful when compiling kernel code.

       -mauto-pic
	   Generate code that is self-relocatable.  This implies
	   -mconstant-gp.  This is useful when compiling firmware code.

       -minline-float-divide-min-latency
	   Generate code for inline divides of floating-point values using the
	   minimum latency algorithm.

       -minline-float-divide-max-throughput
	   Generate code for inline divides of floating-point values using the
	   maximum throughput algorithm.

       -mno-inline-float-divide
	   Do not generate inline code for divides of floating-point values.

       -minline-int-divide-min-latency
	   Generate code for inline divides of integer values using the
	   minimum latency algorithm.

       -minline-int-divide-max-throughput
	   Generate code for inline divides of integer values using the
	   maximum throughput algorithm.

       -mno-inline-int-divide
	   Do not generate inline code for divides of integer values.

       -minline-sqrt-min-latency
	   Generate code for inline square roots using the minimum latency
	   algorithm.

       -minline-sqrt-max-throughput
	   Generate code for inline square roots using the maximum throughput
	   algorithm.

       -mno-inline-sqrt
	   Do not generate inline code for "sqrt".

       -mfused-madd
       -mno-fused-madd
	   Do (don't) generate code that uses the fused multiply/add or
	   multiply/subtract instructions.  The default is to use these
	   instructions.

       -mno-dwarf2-asm
       -mdwarf2-asm
	   Don't (or do) generate assembler code for the DWARF 2 line number
	   debugging info.  This may be useful when not using the GNU
	   assembler.

       -mearly-stop-bits
       -mno-early-stop-bits
	   Allow stop bits to be placed earlier than immediately preceding the
	   instruction that triggered the stop bit.  This can improve
	   instruction scheduling, but does not always do so.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.
	   A fixed register is one that the register allocator cannot use.
	   This is useful when compiling kernel code.  A register range is
	   specified as two registers separated by a dash.  Multiple register
	   ranges can be specified separated by a comma.

       -mtls-size=tls-size
	   Specify bit size of immediate TLS offsets.  Valid values are 14,
	   22, and 64.

       -mtune=cpu-type
	   Tune the instruction scheduling for a particular CPU, Valid values
	   are itanium, itanium1, merced, itanium2, and mckinley.

       -milp32
       -mlp64
	   Generate code for a 32-bit or 64-bit environment.  The 32-bit
	   environment sets int, long and pointer to 32 bits.  The 64-bit
	   environment sets int to 32 bits and long and pointer to 64 bits.
	   These are HP-UX specific flags.

       -mno-sched-br-data-spec
       -msched-br-data-spec
	   (Dis/En)able data speculative scheduling before reload.  This
	   results in generation of "ld.a" instructions and the corresponding
	   check instructions ("ld.c" / "chk.a").  The default is 'disable'.

       -msched-ar-data-spec
       -mno-sched-ar-data-spec
	   (En/Dis)able data speculative scheduling after reload.  This
	   results in generation of "ld.a" instructions and the corresponding
	   check instructions ("ld.c" / "chk.a").  The default is 'enable'.

       -mno-sched-control-spec
       -msched-control-spec
	   (Dis/En)able control speculative scheduling.	 This feature is
	   available only during region scheduling (i.e. before reload).  This
	   results in generation of the "ld.s" instructions and the
	   corresponding check instructions "chk.s".  The default is
	   'disable'.

       -msched-br-in-data-spec
       -mno-sched-br-in-data-spec
	   (En/Dis)able speculative scheduling of the instructions that are
	   dependent on the data speculative loads before reload.  This is
	   effective only with -msched-br-data-spec enabled.  The default is
	   'enable'.

       -msched-ar-in-data-spec
       -mno-sched-ar-in-data-spec
	   (En/Dis)able speculative scheduling of the instructions that are
	   dependent on the data speculative loads after reload.  This is
	   effective only with -msched-ar-data-spec enabled.  The default is
	   'enable'.

       -msched-in-control-spec
       -mno-sched-in-control-spec
	   (En/Dis)able speculative scheduling of the instructions that are
	   dependent on the control speculative loads.	This is effective only
	   with -msched-control-spec enabled.  The default is 'enable'.

       -mno-sched-prefer-non-data-spec-insns
       -msched-prefer-non-data-spec-insns
	   If enabled, data-speculative instructions are chosen for schedule
	   only if there are no other choices at the moment.  This makes the
	   use of the data speculation much more conservative.	The default is
	   'disable'.

       -mno-sched-prefer-non-control-spec-insns
       -msched-prefer-non-control-spec-insns
	   If enabled, control-speculative instructions are chosen for
	   schedule only if there are no other choices at the moment.  This
	   makes the use of the control speculation much more conservative.
	   The default is 'disable'.

       -mno-sched-count-spec-in-critical-path
       -msched-count-spec-in-critical-path
	   If enabled, speculative dependencies are considered during
	   computation of the instructions priorities.	This makes the use of
	   the speculation a bit more conservative.  The default is 'disable'.

       -msched-spec-ldc
	   Use a simple data speculation check.	 This option is on by default.

       -msched-control-spec-ldc
	   Use a simple check for control speculation.	This option is on by
	   default.

       -msched-stop-bits-after-every-cycle
	   Place a stop bit after every cycle when scheduling.	This option is
	   on by default.

       -msched-fp-mem-deps-zero-cost
	   Assume that floating-point stores and loads are not likely to cause
	   a conflict when placed into the same instruction group.  This
	   option is disabled by default.

       -msel-sched-dont-check-control-spec
	   Generate checks for control speculation in selective scheduling.
	   This flag is disabled by default.

       -msched-max-memory-insns=max-insns
	   Limit on the number of memory insns per instruction group, giving
	   lower priority to subsequent memory insns attempting to schedule in
	   the same instruction group. Frequently useful to prevent cache bank
	   conflicts.  The default value is 1.

       -msched-max-memory-insns-hard-limit
	   Makes the limit specified by msched-max-memory-insns a hard limit,
	   disallowing more than that number in an instruction group.
	   Otherwise, the limit is "soft", meaning that non-memory operations
	   are preferred when the limit is reached, but memory operations may
	   still be scheduled.

   LM32 Options
       These -m options are defined for the LatticeMico32 architecture:

       -mbarrel-shift-enabled
	   Enable barrel-shift instructions.

       -mdivide-enabled
	   Enable divide and modulus instructions.

       -mmultiply-enabled
	   Enable multiply instructions.

       -msign-extend-enabled
	   Enable sign extend instructions.

       -muser-enabled
	   Enable user-defined instructions.

   M32C Options
       -mcpu=name
	   Select the CPU for which code is generated.	name may be one of r8c
	   for the R8C/Tiny series, m16c for the M16C (up to /60) series,
	   m32cm for the M16C/80 series, or m32c for the M32C/80 series.

       -msim
	   Specifies that the program will be run on the simulator.  This
	   causes an alternate runtime library to be linked in which supports,
	   for example, file I/O.  You must not use this option when
	   generating programs that will run on real hardware; you must
	   provide your own runtime library for whatever I/O functions are
	   needed.

       -memregs=number
	   Specifies the number of memory-based pseudo-registers GCC uses
	   during code generation.  These pseudo-registers are used like real
	   registers, so there is a tradeoff between GCC's ability to fit the
	   code into available registers, and the performance penalty of using
	   memory instead of registers.	 Note that all modules in a program
	   must be compiled with the same value for this option.  Because of
	   that, you must not use this option with GCC's default runtime
	   libraries.

   M32R/D Options
       These -m options are defined for Renesas M32R/D architectures:

       -m32r2
	   Generate code for the M32R/2.

       -m32rx
	   Generate code for the M32R/X.

       -m32r
	   Generate code for the M32R.	This is the default.

       -mmodel=small
	   Assume all objects live in the lower 16MB of memory (so that their
	   addresses can be loaded with the "ld24" instruction), and assume
	   all subroutines are reachable with the "bl" instruction.  This is
	   the default.

	   The addressability of a particular object can be set with the
	   "model" attribute.

       -mmodel=medium
	   Assume objects may be anywhere in the 32-bit address space (the
	   compiler generates "seth/add3" instructions to load their
	   addresses), and assume all subroutines are reachable with the "bl"
	   instruction.

       -mmodel=large
	   Assume objects may be anywhere in the 32-bit address space (the
	   compiler generates "seth/add3" instructions to load their
	   addresses), and assume subroutines may not be reachable with the
	   "bl" instruction (the compiler generates the much slower
	   "seth/add3/jl" instruction sequence).

       -msdata=none
	   Disable use of the small data area.	Variables are put into one of
	   .data, .bss, or .rodata (unless the "section" attribute has been
	   specified).	This is the default.

	   The small data area consists of sections .sdata and .sbss.  Objects
	   may be explicitly put in the small data area with the "section"
	   attribute using one of these sections.

       -msdata=sdata
	   Put small global and static data in the small data area, but do not
	   generate special code to reference them.

       -msdata=use
	   Put small global and static data in the small data area, and
	   generate special instructions to reference them.

       -G num
	   Put global and static objects less than or equal to num bytes into
	   the small data or BSS sections instead of the normal data or BSS
	   sections.  The default value of num is 8.  The -msdata option must
	   be set to one of sdata or use for this option to have any effect.

	   All modules should be compiled with the same -G num value.
	   Compiling with different values of num may or may not work; if it
	   doesn't the linker gives an error message---incorrect code is not
	   generated.

       -mdebug
	   Makes the M32R-specific code in the compiler display some
	   statistics that might help in debugging programs.

       -malign-loops
	   Align all loops to a 32-byte boundary.

       -mno-align-loops
	   Do not enforce a 32-byte alignment for loops.  This is the default.

       -missue-rate=number
	   Issue number instructions per cycle.	 number can only be 1 or 2.

       -mbranch-cost=number
	   number can only be 1 or 2.  If it is 1 then branches are preferred
	   over conditional code, if it is 2, then the opposite applies.

       -mflush-trap=number
	   Specifies the trap number to use to flush the cache.	 The default
	   is 12.  Valid numbers are between 0 and 15 inclusive.

       -mno-flush-trap
	   Specifies that the cache cannot be flushed by using a trap.

       -mflush-func=name
	   Specifies the name of the operating system function to call to
	   flush the cache.  The default is _flush_cache, but a function call
	   is only used if a trap is not available.

       -mno-flush-func
	   Indicates that there is no OS function for flushing the cache.

   M680x0 Options
       These are the -m options defined for M680x0 and ColdFire processors.
       The default settings depend on which architecture was selected when the
       compiler was configured; the defaults for the most common choices are
       given below.

       -march=arch
	   Generate code for a specific M680x0 or ColdFire instruction set
	   architecture.  Permissible values of arch for M680x0 architectures
	   are: 68000, 68010, 68020, 68030, 68040, 68060 and cpu32.  ColdFire
	   architectures are selected according to Freescale's ISA
	   classification and the permissible values are: isaa, isaaplus, isab
	   and isac.

	   GCC defines a macro __mcfarch__ whenever it is generating code for
	   a ColdFire target.  The arch in this macro is one of the -march
	   arguments given above.

	   When used together, -march and -mtune select code that runs on a
	   family of similar processors but that is optimized for a particular
	   microarchitecture.

       -mcpu=cpu
	   Generate code for a specific M680x0 or ColdFire processor.  The
	   M680x0 cpus are: 68000, 68010, 68020, 68030, 68040, 68060, 68302,
	   68332 and cpu32.  The ColdFire cpus are given by the table below,
	   which also classifies the CPUs into families:

	   Family : -mcpu arguments
	   51 : 51 51ac 51ag 51cn 51em 51je 51jf 51jg 51jm 51mm 51qe 51qm
	   5206 : 5202 5204 5206
	   5206e : 5206e
	   5208 : 5207 5208
	   5211a : 5210a 5211a
	   5213 : 5211 5212 5213
	   5216 : 5214 5216
	   52235 : 52230 52231 52232 52233 52234 52235
	   5225 : 5224 5225
	   52259 : 52252 52254 52255 52256 52258 52259
	   5235 : 5232 5233 5234 5235 523x
	   5249 : 5249
	   5250 : 5250
	   5271 : 5270 5271
	   5272 : 5272
	   5275 : 5274 5275
	   5282 : 5280 5281 5282 528x
	   53017 : 53011 53012 53013 53014 53015 53016 53017
	   5307 : 5307
	   5329 : 5327 5328 5329 532x
	   5373 : 5372 5373 537x
	   5407 : 5407
	   5475 : 5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483 5484
	   5485

	   -mcpu=cpu overrides -march=arch if arch is compatible with cpu.
	   Other combinations of -mcpu and -march are rejected.

	   GCC defines the macro __mcf_cpu_cpu when ColdFire target cpu is
	   selected.  It also defines __mcf_family_family, where the value of
	   family is given by the table above.

       -mtune=tune
	   Tune the code for a particular microarchitecture within the
	   constraints set by -march and -mcpu.	 The M680x0 microarchitectures
	   are: 68000, 68010, 68020, 68030, 68040, 68060 and cpu32.  The
	   ColdFire microarchitectures are: cfv1, cfv2, cfv3, cfv4 and cfv4e.

	   You can also use -mtune=68020-40 for code that needs to run
	   relatively well on 68020, 68030 and 68040 targets.  -mtune=68020-60
	   is similar but includes 68060 targets as well.  These two options
	   select the same tuning decisions as -m68020-40 and -m68020-60
	   respectively.

	   GCC defines the macros __mcarch and __mcarch__ when tuning for
	   680x0 architecture arch.  It also defines mcarch unless either
	   -ansi or a non-GNU -std option is used.  If GCC is tuning for a
	   range of architectures, as selected by -mtune=68020-40 or
	   -mtune=68020-60, it defines the macros for every architecture in
	   the range.

	   GCC also defines the macro __muarch__ when tuning for ColdFire
	   microarchitecture uarch, where uarch is one of the arguments given
	   above.

       -m68000
       -mc68000
	   Generate output for a 68000.	 This is the default when the compiler
	   is configured for 68000-based systems.  It is equivalent to
	   -march=68000.

	   Use this option for microcontrollers with a 68000 or EC000 core,
	   including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.

       -m68010
	   Generate output for a 68010.	 This is the default when the compiler
	   is configured for 68010-based systems.  It is equivalent to
	   -march=68010.

       -m68020
       -mc68020
	   Generate output for a 68020.	 This is the default when the compiler
	   is configured for 68020-based systems.  It is equivalent to
	   -march=68020.

       -m68030
	   Generate output for a 68030.	 This is the default when the compiler
	   is configured for 68030-based systems.  It is equivalent to
	   -march=68030.

       -m68040
	   Generate output for a 68040.	 This is the default when the compiler
	   is configured for 68040-based systems.  It is equivalent to
	   -march=68040.

	   This option inhibits the use of 68881/68882 instructions that have
	   to be emulated by software on the 68040.  Use this option if your
	   68040 does not have code to emulate those instructions.

       -m68060
	   Generate output for a 68060.	 This is the default when the compiler
	   is configured for 68060-based systems.  It is equivalent to
	   -march=68060.

	   This option inhibits the use of 68020 and 68881/68882 instructions
	   that have to be emulated by software on the 68060.  Use this option
	   if your 68060 does not have code to emulate those instructions.

       -mcpu32
	   Generate output for a CPU32.	 This is the default when the compiler
	   is configured for CPU32-based systems.  It is equivalent to
	   -march=cpu32.

	   Use this option for microcontrollers with a CPU32 or CPU32+ core,
	   including the 68330, 68331, 68332, 68333, 68334, 68336, 68340,
	   68341, 68349 and 68360.

       -m5200
	   Generate output for a 520X ColdFire CPU.  This is the default when
	   the compiler is configured for 520X-based systems.  It is
	   equivalent to -mcpu=5206, and is now deprecated in favor of that
	   option.

	   Use this option for microcontroller with a 5200 core, including the
	   MCF5202, MCF5203, MCF5204 and MCF5206.

       -m5206e
	   Generate output for a 5206e ColdFire CPU.  The option is now
	   deprecated in favor of the equivalent -mcpu=5206e.

       -m528x
	   Generate output for a member of the ColdFire 528X family.  The
	   option is now deprecated in favor of the equivalent -mcpu=528x.

       -m5307
	   Generate output for a ColdFire 5307 CPU.  The option is now
	   deprecated in favor of the equivalent -mcpu=5307.

       -m5407
	   Generate output for a ColdFire 5407 CPU.  The option is now
	   deprecated in favor of the equivalent -mcpu=5407.

       -mcfv4e
	   Generate output for a ColdFire V4e family CPU (e.g. 547x/548x).
	   This includes use of hardware floating-point instructions.  The
	   option is equivalent to -mcpu=547x, and is now deprecated in favor
	   of that option.

       -m68020-40
	   Generate output for a 68040, without using any of the new
	   instructions.  This results in code that can run relatively
	   efficiently on either a 68020/68881 or a 68030 or a 68040.  The
	   generated code does use the 68881 instructions that are emulated on
	   the 68040.

	   The option is equivalent to -march=68020 -mtune=68020-40.

       -m68020-60
	   Generate output for a 68060, without using any of the new
	   instructions.  This results in code that can run relatively
	   efficiently on either a 68020/68881 or a 68030 or a 68040.  The
	   generated code does use the 68881 instructions that are emulated on
	   the 68060.

	   The option is equivalent to -march=68020 -mtune=68020-60.

       -mhard-float
       -m68881
	   Generate floating-point instructions.  This is the default for
	   68020 and above, and for ColdFire devices that have an FPU.	It
	   defines the macro __HAVE_68881__ on M680x0 targets and __mcffpu__
	   on ColdFire targets.

       -msoft-float
	   Do not generate floating-point instructions; use library calls
	   instead.  This is the default for 68000, 68010, and 68832 targets.
	   It is also the default for ColdFire devices that have no FPU.

       -mdiv
       -mno-div
	   Generate (do not generate) ColdFire hardware divide and remainder
	   instructions.  If -march is used without -mcpu, the default is "on"
	   for ColdFire architectures and "off" for M680x0 architectures.
	   Otherwise, the default is taken from the target CPU (either the
	   default CPU, or the one specified by -mcpu).	 For example, the
	   default is "off" for -mcpu=5206 and "on" for -mcpu=5206e.

	   GCC defines the macro __mcfhwdiv__ when this option is enabled.

       -mshort
	   Consider type "int" to be 16 bits wide, like "short int".
	   Additionally, parameters passed on the stack are also aligned to a
	   16-bit boundary even on targets whose API mandates promotion to
	   32-bit.

       -mno-short
	   Do not consider type "int" to be 16 bits wide.  This is the
	   default.

       -mnobitfield
       -mno-bitfield
	   Do not use the bit-field instructions.  The -m68000, -mcpu32 and
	   -m5200 options imply -mnobitfield.

       -mbitfield
	   Do use the bit-field instructions.  The -m68020 option implies
	   -mbitfield.	This is the default if you use a configuration
	   designed for a 68020.

       -mrtd
	   Use a different function-calling convention, in which functions
	   that take a fixed number of arguments return with the "rtd"
	   instruction, which pops their arguments while returning.  This
	   saves one instruction in the caller since there is no need to pop
	   the arguments there.

	   This calling convention is incompatible with the one normally used
	   on Unix, so you cannot use it if you need to call libraries
	   compiled with the Unix compiler.

	   Also, you must provide function prototypes for all functions that
	   take variable numbers of arguments (including "printf"); otherwise
	   incorrect code is generated for calls to those functions.

	   In addition, seriously incorrect code results if you call a
	   function with too many arguments.  (Normally, extra arguments are
	   harmlessly ignored.)

	   The "rtd" instruction is supported by the 68010, 68020, 68030,
	   68040, 68060 and CPU32 processors, but not by the 68000 or 5200.

       -mno-rtd
	   Do not use the calling conventions selected by -mrtd.  This is the
	   default.

       -malign-int
       -mno-align-int
	   Control whether GCC aligns "int", "long", "long long", "float",
	   "double", and "long double" variables on a 32-bit boundary
	   (-malign-int) or a 16-bit boundary (-mno-align-int).	 Aligning
	   variables on 32-bit boundaries produces code that runs somewhat
	   faster on processors with 32-bit busses at the expense of more
	   memory.

	   Warning: if you use the -malign-int switch, GCC aligns structures
	   containing the above types differently than most published
	   application binary interface specifications for the m68k.

       -mpcrel
	   Use the pc-relative addressing mode of the 68000 directly, instead
	   of using a global offset table.  At present, this option implies
	   -fpic, allowing at most a 16-bit offset for pc-relative addressing.
	   -fPIC is not presently supported with -mpcrel, though this could be
	   supported for 68020 and higher processors.

       -mno-strict-align
       -mstrict-align
	   Do not (do) assume that unaligned memory references are handled by
	   the system.

       -msep-data
	   Generate code that allows the data segment to be located in a
	   different area of memory from the text segment.  This allows for
	   execute-in-place in an environment without virtual memory
	   management.	This option implies -fPIC.

       -mno-sep-data
	   Generate code that assumes that the data segment follows the text
	   segment.  This is the default.

       -mid-shared-library
	   Generate code that supports shared libraries via the library ID
	   method.  This allows for execute-in-place and shared libraries in
	   an environment without virtual memory management.  This option
	   implies -fPIC.

       -mno-id-shared-library
	   Generate code that doesn't assume ID-based shared libraries are
	   being used.	This is the default.

       -mshared-library-id=n
	   Specifies the identification number of the ID-based shared library
	   being compiled.  Specifying a value of 0 generates more compact
	   code; specifying other values forces the allocation of that number
	   to the current library, but is no more space- or time-efficient
	   than omitting this option.

       -mxgot
       -mno-xgot
	   When generating position-independent code for ColdFire, generate
	   code that works if the GOT has more than 8192 entries.  This code
	   is larger and slower than code generated without this option.  On
	   M680x0 processors, this option is not needed; -fPIC suffices.

	   GCC normally uses a single instruction to load values from the GOT.
	   While this is relatively efficient, it only works if the GOT is
	   smaller than about 64k.  Anything larger causes the linker to
	   report an error such as:

		   relocation truncated to fit: R_68K_GOT16O foobar

	   If this happens, you should recompile your code with -mxgot.	 It
	   should then work with very large GOTs.  However, code generated
	   with -mxgot is less efficient, since it takes 4 instructions to
	   fetch the value of a global symbol.

	   Note that some linkers, including newer versions of the GNU linker,
	   can create multiple GOTs and sort GOT entries.  If you have such a
	   linker, you should only need to use -mxgot when compiling a single
	   object file that accesses more than 8192 GOT entries.  Very few do.

	   These options have no effect unless GCC is generating position-
	   independent code.

   MCore Options
       These are the -m options defined for the Motorola M*Core processors.

       -mhardlit
       -mno-hardlit
	   Inline constants into the code stream if it can be done in two
	   instructions or less.

       -mdiv
       -mno-div
	   Use the divide instruction.	(Enabled by default).

       -mrelax-immediate
       -mno-relax-immediate
	   Allow arbitrary-sized immediates in bit operations.

       -mwide-bitfields
       -mno-wide-bitfields
	   Always treat bit-fields as "int"-sized.

       -m4byte-functions
       -mno-4byte-functions
	   Force all functions to be aligned to a 4-byte boundary.

       -mcallgraph-data
       -mno-callgraph-data
	   Emit callgraph information.

       -mslow-bytes
       -mno-slow-bytes
	   Prefer word access when reading byte quantities.

       -mlittle-endian
       -mbig-endian
	   Generate code for a little-endian target.

       -m210
       -m340
	   Generate code for the 210 processor.

       -mno-lsim
	   Assume that runtime support has been provided and so omit the
	   simulator library (libsim.a) from the linker command line.

       -mstack-increment=size
	   Set the maximum amount for a single stack increment operation.
	   Large values can increase the speed of programs that contain
	   functions that need a large amount of stack space, but they can
	   also trigger a segmentation fault if the stack is extended too
	   much.  The default value is 0x1000.

   MeP Options
       -mabsdiff
	   Enables the "abs" instruction, which is the absolute difference
	   between two registers.

       -mall-opts
	   Enables all the optional instructions---average, multiply, divide,
	   bit operations, leading zero, absolute difference, min/max, clip,
	   and saturation.

       -maverage
	   Enables the "ave" instruction, which computes the average of two
	   registers.

       -mbased=n
	   Variables of size n bytes or smaller are placed in the ".based"
	   section by default.	Based variables use the $tp register as a base
	   register, and there is a 128-byte limit to the ".based" section.

       -mbitops
	   Enables the bit operation instructions---bit test ("btstm"), set
	   ("bsetm"), clear ("bclrm"), invert ("bnotm"), and test-and-set
	   ("tas").

       -mc=name
	   Selects which section constant data is placed in.  name may be
	   "tiny", "near", or "far".

       -mclip
	   Enables the "clip" instruction.  Note that "-mclip" is not useful
	   unless you also provide "-mminmax".

       -mconfig=name
	   Selects one of the built-in core configurations.  Each MeP chip has
	   one or more modules in it; each module has a core CPU and a variety
	   of coprocessors, optional instructions, and peripherals.  The
	   "MeP-Integrator" tool, not part of GCC, provides these
	   configurations through this option; using this option is the same
	   as using all the corresponding command-line options.	 The default
	   configuration is "default".

       -mcop
	   Enables the coprocessor instructions.  By default, this is a 32-bit
	   coprocessor.	 Note that the coprocessor is normally enabled via the
	   "-mconfig=" option.

       -mcop32
	   Enables the 32-bit coprocessor's instructions.

       -mcop64
	   Enables the 64-bit coprocessor's instructions.

       -mivc2
	   Enables IVC2 scheduling.  IVC2 is a 64-bit VLIW coprocessor.

       -mdc
	   Causes constant variables to be placed in the ".near" section.

       -mdiv
	   Enables the "div" and "divu" instructions.

       -meb
	   Generate big-endian code.

       -mel
	   Generate little-endian code.

       -mio-volatile
	   Tells the compiler that any variable marked with the "io" attribute
	   is to be considered volatile.

       -ml Causes variables to be assigned to the ".far" section by default.

       -mleadz
	   Enables the "leadz" (leading zero) instruction.

       -mm Causes variables to be assigned to the ".near" section by default.

       -mminmax
	   Enables the "min" and "max" instructions.

       -mmult
	   Enables the multiplication and multiply-accumulate instructions.

       -mno-opts
	   Disables all the optional instructions enabled by "-mall-opts".

       -mrepeat
	   Enables the "repeat" and "erepeat" instructions, used for low-
	   overhead looping.

       -ms Causes all variables to default to the ".tiny" section.  Note that
	   there is a 65536-byte limit to this section.	 Accesses to these
	   variables use the %gp base register.

       -msatur
	   Enables the saturation instructions.	 Note that the compiler does
	   not currently generate these itself, but this option is included
	   for compatibility with other tools, like "as".

       -msdram
	   Link the SDRAM-based runtime instead of the default ROM-based
	   runtime.

       -msim
	   Link the simulator runtime libraries.

       -msimnovec
	   Link the simulator runtime libraries, excluding built-in support
	   for reset and exception vectors and tables.

       -mtf
	   Causes all functions to default to the ".far" section.  Without
	   this option, functions default to the ".near" section.

       -mtiny=n
	   Variables that are n bytes or smaller are allocated to the ".tiny"
	   section.  These variables use the $gp base register.	 The default
	   for this option is 4, but note that there's a 65536-byte limit to
	   the ".tiny" section.

   MicroBlaze Options
       -msoft-float
	   Use software emulation for floating point (default).

       -mhard-float
	   Use hardware floating-point instructions.

       -mmemcpy
	   Do not optimize block moves, use "memcpy".

       -mno-clearbss
	   This option is deprecated.  Use -fno-zero-initialized-in-bss
	   instead.

       -mcpu=cpu-type
	   Use features of, and schedule code for, the given CPU.  Supported
	   values are in the format vX.YY.Z, where X is a major version, YY is
	   the minor version, and Z is compatibility code.  Example values are
	   v3.00.a, v4.00.b, v5.00.a, v5.00.b, v5.00.b, v6.00.a.

       -mxl-soft-mul
	   Use software multiply emulation (default).

       -mxl-soft-div
	   Use software emulation for divides (default).

       -mxl-barrel-shift
	   Use the hardware barrel shifter.

       -mxl-pattern-compare
	   Use pattern compare instructions.

       -msmall-divides
	   Use table lookup optimization for small signed integer divisions.

       -mxl-stack-check
	   This option is deprecated.  Use -fstack-check instead.

       -mxl-gp-opt
	   Use GP-relative ".sdata"/".sbss" sections.

       -mxl-multiply-high
	   Use multiply high instructions for high part of 32x32 multiply.

       -mxl-float-convert
	   Use hardware floating-point conversion instructions.

       -mxl-float-sqrt
	   Use hardware floating-point square root instruction.

       -mbig-endian
	   Generate code for a big-endian target.

       -mlittle-endian
	   Generate code for a little-endian target.

       -mxl-reorder
	   Use reorder instructions (swap and byte reversed load/store).

       -mxl-mode-app-model
	   Select application model app-model.	Valid models are

	   executable
	       normal executable (default), uses startup code crt0.o.

	   xmdstub
	       for use with Xilinx Microprocessor Debugger (XMD) based
	       software intrusive debug agent called xmdstub. This uses
	       startup file crt1.o and sets the start address of the program
	       to 0x800.

	   bootstrap
	       for applications that are loaded using a bootloader.  This
	       model uses startup file crt2.o which does not contain a
	       processor reset vector handler. This is suitable for
	       transferring control on a processor reset to the bootloader
	       rather than the application.

	   novectors
	       for applications that do not require any of the MicroBlaze
	       vectors. This option may be useful for applications running
	       within a monitoring application. This model uses crt3.o as a
	       startup file.

	   Option -xl-mode-app-model is a deprecated alias for -mxl-mode-app-
	   model.

   MIPS Options
       -EB Generate big-endian code.

       -EL Generate little-endian code.	 This is the default for mips*el-*-*
	   configurations.

       -march=arch
	   Generate code that runs on arch, which can be the name of a generic
	   MIPS ISA, or the name of a particular processor.  The ISA names
	   are: mips1, mips2, mips3, mips4, mips32, mips32r2, mips64 and
	   mips64r2.  The processor names are: 4kc, 4km, 4kp, 4ksc, 4kec,
	   4kem, 4kep, 4ksd, 5kc, 5kf, 20kc, 24kc, 24kf2_1, 24kf1_1, 24kec,
	   24kef2_1, 24kef1_1, 34kc, 34kf2_1, 34kf1_1, 34kn, 74kc, 74kf2_1,
	   74kf1_1, 74kf3_2, 1004kc, 1004kf2_1, 1004kf1_1, loongson2e,
	   loongson2f, loongson3a, m4k, octeon, octeon+, octeon2, orion,
	   r2000, r3000, r3900, r4000, r4400, r4600, r4650, r4700, r6000,
	   r8000, rm7000, rm9000, r10000, r12000, r14000, r16000, sb1,
	   sr71000, vr4100, vr4111, vr4120, vr4130, vr4300, vr5000, vr5400,
	   vr5500, xlr and xlp.	 The special value from-abi selects the most
	   compatible architecture for the selected ABI (that is, mips1 for
	   32-bit ABIs and mips3 for 64-bit ABIs).

	   The native Linux/GNU toolchain also supports the value native,
	   which selects the best architecture option for the host processor.
	   -march=native has no effect if GCC does not recognize the
	   processor.

	   In processor names, a final 000 can be abbreviated as k (for
	   example, -march=r2k).  Prefixes are optional, and vr may be written
	   r.

	   Names of the form nf2_1 refer to processors with FPUs clocked at
	   half the rate of the core, names of the form nf1_1 refer to
	   processors with FPUs clocked at the same rate as the core, and
	   names of the form nf3_2 refer to processors with FPUs clocked a
	   ratio of 3:2 with respect to the core.  For compatibility reasons,
	   nf is accepted as a synonym for nf2_1 while nx and bfx are accepted
	   as synonyms for nf1_1.

	   GCC defines two macros based on the value of this option.  The
	   first is _MIPS_ARCH, which gives the name of target architecture,
	   as a string.	 The second has the form _MIPS_ARCH_foo, where foo is
	   the capitalized value of _MIPS_ARCH.	 For example, -march=r2000
	   sets _MIPS_ARCH to "r2000" and defines the macro _MIPS_ARCH_R2000.

	   Note that the _MIPS_ARCH macro uses the processor names given
	   above.  In other words, it has the full prefix and does not
	   abbreviate 000 as k.	 In the case of from-abi, the macro names the
	   resolved architecture (either "mips1" or "mips3").  It names the
	   default architecture when no -march option is given.

       -mtune=arch
	   Optimize for arch.  Among other things, this option controls the
	   way instructions are scheduled, and the perceived cost of
	   arithmetic operations.  The list of arch values is the same as for
	   -march.

	   When this option is not used, GCC optimizes for the processor
	   specified by -march.	 By using -march and -mtune together, it is
	   possible to generate code that runs on a family of processors, but
	   optimize the code for one particular member of that family.

	   -mtune defines the macros _MIPS_TUNE and _MIPS_TUNE_foo, which work
	   in the same way as the -march ones described above.

       -mips1
	   Equivalent to -march=mips1.

       -mips2
	   Equivalent to -march=mips2.

       -mips3
	   Equivalent to -march=mips3.

       -mips4
	   Equivalent to -march=mips4.

       -mips32
	   Equivalent to -march=mips32.

       -mips32r2
	   Equivalent to -march=mips32r2.

       -mips64
	   Equivalent to -march=mips64.

       -mips64r2
	   Equivalent to -march=mips64r2.

       -mips16
       -mno-mips16
	   Generate (do not generate) MIPS16 code.  If GCC is targeting a
	   MIPS32 or MIPS64 architecture, it makes use of the MIPS16e ASE.

	   MIPS16 code generation can also be controlled on a per-function
	   basis by means of "mips16" and "nomips16" attributes.

       -mflip-mips16
	   Generate MIPS16 code on alternating functions.  This option is
	   provided for regression testing of mixed MIPS16/non-MIPS16 code
	   generation, and is not intended for ordinary use in compiling user
	   code.

       -minterlink-mips16
       -mno-interlink-mips16
	   Require (do not require) that non-MIPS16 code be link-compatible
	   with MIPS16 code.

	   For example, non-MIPS16 code cannot jump directly to MIPS16 code;
	   it must either use a call or an indirect jump.  -minterlink-mips16
	   therefore disables direct jumps unless GCC knows that the target of
	   the jump is not MIPS16.

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
	   Generate code for the given ABI.

	   Note that the EABI has a 32-bit and a 64-bit variant.  GCC normally
	   generates 64-bit code when you select a 64-bit architecture, but
	   you can use -mgp32 to get 32-bit code instead.

	   For information about the O64 ABI, see
	   <http://gcc.gnu.org/projects/mipso64-abi.html>.

	   GCC supports a variant of the o32 ABI in which floating-point
	   registers are 64 rather than 32 bits wide.  You can select this
	   combination with -mabi=32 -mfp64.  This ABI relies on the "mthc1"
	   and "mfhc1" instructions and is therefore only supported for
	   MIPS32R2 processors.

	   The register assignments for arguments and return values remain the
	   same, but each scalar value is passed in a single 64-bit register
	   rather than a pair of 32-bit registers.  For example, scalar
	   floating-point values are returned in $f0 only, not a $f0/$f1 pair.
	   The set of call-saved registers also remains the same, but all 64
	   bits are saved.

       -mabicalls
       -mno-abicalls
	   Generate (do not generate) code that is suitable for SVR4-style
	   dynamic objects.  -mabicalls is the default for SVR4-based systems.

       -mshared
       -mno-shared
	   Generate (do not generate) code that is fully position-independent,
	   and that can therefore be linked into shared libraries.  This
	   option only affects -mabicalls.

	   All -mabicalls code has traditionally been position-independent,
	   regardless of options like -fPIC and -fpic.	However, as an
	   extension, the GNU toolchain allows executables to use absolute
	   accesses for locally-binding symbols.  It can also use shorter GP
	   initialization sequences and generate direct calls to locally-
	   defined functions.  This mode is selected by -mno-shared.

	   -mno-shared depends on binutils 2.16 or higher and generates
	   objects that can only be linked by the GNU linker.  However, the
	   option does not affect the ABI of the final executable; it only
	   affects the ABI of relocatable objects.  Using -mno-shared
	   generally makes executables both smaller and quicker.

	   -mshared is the default.

       -mplt
       -mno-plt
	   Assume (do not assume) that the static and dynamic linkers support
	   PLTs and copy relocations.  This option only affects -mno-shared
	   -mabicalls.	For the n64 ABI, this option has no effect without
	   -msym32.

	   You can make -mplt the default by configuring GCC with
	   --with-mips-plt.  The default is -mno-plt otherwise.

       -mxgot
       -mno-xgot
	   Lift (do not lift) the usual restrictions on the size of the global
	   offset table.

	   GCC normally uses a single instruction to load values from the GOT.
	   While this is relatively efficient, it only works if the GOT is
	   smaller than about 64k.  Anything larger causes the linker to
	   report an error such as:

		   relocation truncated to fit: R_MIPS_GOT16 foobar

	   If this happens, you should recompile your code with -mxgot.	 This
	   works with very large GOTs, although the code is also less
	   efficient, since it takes three instructions to fetch the value of
	   a global symbol.

	   Note that some linkers can create multiple GOTs.  If you have such
	   a linker, you should only need to use -mxgot when a single object
	   file accesses more than 64k's worth of GOT entries.	Very few do.

	   These options have no effect unless GCC is generating position
	   independent code.

       -mgp32
	   Assume that general-purpose registers are 32 bits wide.

       -mgp64
	   Assume that general-purpose registers are 64 bits wide.

       -mfp32
	   Assume that floating-point registers are 32 bits wide.

       -mfp64
	   Assume that floating-point registers are 64 bits wide.

       -mhard-float
	   Use floating-point coprocessor instructions.

       -msoft-float
	   Do not use floating-point coprocessor instructions.	Implement
	   floating-point calculations using library calls instead.

       -mno-float
	   Equivalent to -msoft-float, but additionally asserts that the
	   program being compiled does not perform any floating-point
	   operations.	This option is presently supported only by some bare-
	   metal MIPS configurations, where it may select a special set of
	   libraries that lack all floating-point support (including, for
	   example, the floating-point "printf" formats).  If code compiled
	   with "-mno-float" accidentally contains floating-point operations,
	   it is likely to suffer a link-time or run-time failure.

       -msingle-float
	   Assume that the floating-point coprocessor only supports single-
	   precision operations.

       -mdouble-float
	   Assume that the floating-point coprocessor supports double-
	   precision operations.  This is the default.

       -mllsc
       -mno-llsc
	   Use (do not use) ll, sc, and sync instructions to implement atomic
	   memory built-in functions.  When neither option is specified, GCC
	   uses the instructions if the target architecture supports them.

	   -mllsc is useful if the runtime environment can emulate the
	   instructions and -mno-llsc can be useful when compiling for
	   nonstandard ISAs.  You can make either option the default by
	   configuring GCC with --with-llsc and --without-llsc respectively.
	   --with-llsc is the default for some configurations; see the
	   installation documentation for details.

       -mdsp
       -mno-dsp
	   Use (do not use) revision 1 of the MIPS DSP ASE.
	     This option defines the preprocessor macro __mips_dsp.  It also
	   defines __mips_dsp_rev to 1.

       -mdspr2
       -mno-dspr2
	   Use (do not use) revision 2 of the MIPS DSP ASE.
	     This option defines the preprocessor macros __mips_dsp and
	   __mips_dspr2.  It also defines __mips_dsp_rev to 2.

       -msmartmips
       -mno-smartmips
	   Use (do not use) the MIPS SmartMIPS ASE.

       -mpaired-single
       -mno-paired-single
	   Use (do not use) paired-single floating-point instructions.
	     This option requires hardware floating-point support to be
	   enabled.

       -mdmx
       -mno-mdmx
	   Use (do not use) MIPS Digital Media Extension instructions.	This
	   option can only be used when generating 64-bit code and requires
	   hardware floating-point support to be enabled.

       -mips3d
       -mno-mips3d
	   Use (do not use) the MIPS-3D ASE.  The option -mips3d implies
	   -mpaired-single.

       -mmt
       -mno-mt
	   Use (do not use) MT Multithreading instructions.

       -mmcu
       -mno-mcu
	   Use (do not use) the MIPS MCU ASE instructions.

       -mlong64
	   Force "long" types to be 64 bits wide.  See -mlong32 for an
	   explanation of the default and the way that the pointer size is
	   determined.

       -mlong32
	   Force "long", "int", and pointer types to be 32 bits wide.

	   The default size of "int"s, "long"s and pointers depends on the
	   ABI.	 All the supported ABIs use 32-bit "int"s.  The n64 ABI uses
	   64-bit "long"s, as does the 64-bit EABI; the others use 32-bit
	   "long"s.  Pointers are the same size as "long"s, or the same size
	   as integer registers, whichever is smaller.

       -msym32
       -mno-sym32
	   Assume (do not assume) that all symbols have 32-bit values,
	   regardless of the selected ABI.  This option is useful in
	   combination with -mabi=64 and -mno-abicalls because it allows GCC
	   to generate shorter and faster references to symbolic addresses.

       -G num
	   Put definitions of externally-visible data in a small data section
	   if that data is no bigger than num bytes.  GCC can then generate
	   more efficient accesses to the data; see -mgpopt for details.

	   The default -G option depends on the configuration.

       -mlocal-sdata
       -mno-local-sdata
	   Extend (do not extend) the -G behavior to local data too, such as
	   to static variables in C.  -mlocal-sdata is the default for all
	   configurations.

	   If the linker complains that an application is using too much small
	   data, you might want to try rebuilding the less performance-
	   critical parts with -mno-local-sdata.  You might also want to build
	   large libraries with -mno-local-sdata, so that the libraries leave
	   more room for the main program.

       -mextern-sdata
       -mno-extern-sdata
	   Assume (do not assume) that externally-defined data is in a small
	   data section if the size of that data is within the -G limit.
	   -mextern-sdata is the default for all configurations.

	   If you compile a module Mod with -mextern-sdata -G num -mgpopt, and
	   Mod references a variable Var that is no bigger than num bytes, you
	   must make sure that Var is placed in a small data section.  If Var
	   is defined by another module, you must either compile that module
	   with a high-enough -G setting or attach a "section" attribute to
	   Var's definition.  If Var is common, you must link the application
	   with a high-enough -G setting.

	   The easiest way of satisfying these restrictions is to compile and
	   link every module with the same -G option.  However, you may wish
	   to build a library that supports several different small data
	   limits.  You can do this by compiling the library with the highest
	   supported -G setting and additionally using -mno-extern-sdata to
	   stop the library from making assumptions about externally-defined
	   data.

       -mgpopt
       -mno-gpopt
	   Use (do not use) GP-relative accesses for symbols that are known to
	   be in a small data section; see -G, -mlocal-sdata and
	   -mextern-sdata.  -mgpopt is the default for all configurations.

	   -mno-gpopt is useful for cases where the $gp register might not
	   hold the value of "_gp".  For example, if the code is part of a
	   library that might be used in a boot monitor, programs that call
	   boot monitor routines pass an unknown value in $gp.	(In such
	   situations, the boot monitor itself is usually compiled with -G0.)

	   -mno-gpopt implies -mno-local-sdata and -mno-extern-sdata.

       -membedded-data
       -mno-embedded-data
	   Allocate variables to the read-only data section first if possible,
	   then next in the small data section if possible, otherwise in data.
	   This gives slightly slower code than the default, but reduces the
	   amount of RAM required when executing, and thus may be preferred
	   for some embedded systems.

       -muninit-const-in-rodata
       -mno-uninit-const-in-rodata
	   Put uninitialized "const" variables in the read-only data section.
	   This option is only meaningful in conjunction with -membedded-data.

       -mcode-readable=setting
	   Specify whether GCC may generate code that reads from executable
	   sections.  There are three possible settings:

	   -mcode-readable=yes
	       Instructions may freely access executable sections.  This is
	       the default setting.

	   -mcode-readable=pcrel
	       MIPS16 PC-relative load instructions can access executable
	       sections, but other instructions must not do so.	 This option
	       is useful on 4KSc and 4KSd processors when the code TLBs have
	       the Read Inhibit bit set.  It is also useful on processors that
	       can be configured to have a dual instruction/data SRAM
	       interface and that, like the M4K, automatically redirect PC-
	       relative loads to the instruction RAM.

	   -mcode-readable=no
	       Instructions must not access executable sections.  This option
	       can be useful on targets that are configured to have a dual
	       instruction/data SRAM interface but that (unlike the M4K) do
	       not automatically redirect PC-relative loads to the instruction
	       RAM.

       -msplit-addresses
       -mno-split-addresses
	   Enable (disable) use of the "%hi()" and "%lo()" assembler
	   relocation operators.  This option has been superseded by
	   -mexplicit-relocs but is retained for backwards compatibility.

       -mexplicit-relocs
       -mno-explicit-relocs
	   Use (do not use) assembler relocation operators when dealing with
	   symbolic addresses.	The alternative, selected by
	   -mno-explicit-relocs, is to use assembler macros instead.

	   -mexplicit-relocs is the default if GCC was configured to use an
	   assembler that supports relocation operators.

       -mcheck-zero-division
       -mno-check-zero-division
	   Trap (do not trap) on integer division by zero.

	   The default is -mcheck-zero-division.

       -mdivide-traps
       -mdivide-breaks
	   MIPS systems check for division by zero by generating either a
	   conditional trap or a break instruction.  Using traps results in
	   smaller code, but is only supported on MIPS II and later.  Also,
	   some versions of the Linux kernel have a bug that prevents trap
	   from generating the proper signal ("SIGFPE").  Use -mdivide-traps
	   to allow conditional traps on architectures that support them and
	   -mdivide-breaks to force the use of breaks.

	   The default is usually -mdivide-traps, but this can be overridden
	   at configure time using --with-divide=breaks.  Divide-by-zero
	   checks can be completely disabled using -mno-check-zero-division.

       -mmemcpy
       -mno-memcpy
	   Force (do not force) the use of "memcpy()" for non-trivial block
	   moves.  The default is -mno-memcpy, which allows GCC to inline most
	   constant-sized copies.

       -mlong-calls
       -mno-long-calls
	   Disable (do not disable) use of the "jal" instruction.  Calling
	   functions using "jal" is more efficient but requires the caller and
	   callee to be in the same 256 megabyte segment.

	   This option has no effect on abicalls code.	The default is
	   -mno-long-calls.

       -mmad
       -mno-mad
	   Enable (disable) use of the "mad", "madu" and "mul" instructions,
	   as provided by the R4650 ISA.

       -mfused-madd
       -mno-fused-madd
	   Enable (disable) use of the floating-point multiply-accumulate
	   instructions, when they are available.  The default is
	   -mfused-madd.

	   On the R8000 CPU when multiply-accumulate instructions are used,
	   the intermediate product is calculated to infinite precision and is
	   not subject to the FCSR Flush to Zero bit.  This may be undesirable
	   in some circumstances.  On other processors the result is
	   numerically identical to the equivalent computation using separate
	   multiply, add, subtract and negate instructions.

       -nocpp
	   Tell the MIPS assembler to not run its preprocessor over user
	   assembler files (with a .s suffix) when assembling them.

       -mfix-24k
       -mno-fix-24k
	   Work around the 24K E48 (lost data on stores during refill) errata.
	   The workarounds are implemented by the assembler rather than by
	   GCC.

       -mfix-r4000
       -mno-fix-r4000
	   Work around certain R4000 CPU errata:

	   -   A double-word or a variable shift may give an incorrect result
	       if executed immediately after starting an integer division.

	   -   A double-word or a variable shift may give an incorrect result
	       if executed while an integer multiplication is in progress.

	   -   An integer division may give an incorrect result if started in
	       a delay slot of a taken branch or a jump.

       -mfix-r4400
       -mno-fix-r4400
	   Work around certain R4400 CPU errata:

	   -   A double-word or a variable shift may give an incorrect result
	       if executed immediately after starting an integer division.

       -mfix-r10000
       -mno-fix-r10000
	   Work around certain R10000 errata:

	   -   "ll"/"sc" sequences may not behave atomically on revisions
	       prior to 3.0.  They may deadlock on revisions 2.6 and earlier.

	   This option can only be used if the target architecture supports
	   branch-likely instructions.	-mfix-r10000 is the default when
	   -march=r10000 is used; -mno-fix-r10000 is the default otherwise.

       -mfix-vr4120
       -mno-fix-vr4120
	   Work around certain VR4120 errata:

	   -   "dmultu" does not always produce the correct result.

	   -   "div" and "ddiv" do not always produce the correct result if
	       one of the operands is negative.

	   The workarounds for the division errata rely on special functions
	   in libgcc.a.	 At present, these functions are only provided by the
	   "mips64vr*-elf" configurations.

	   Other VR4120 errata require a NOP to be inserted between certain
	   pairs of instructions.  These errata are handled by the assembler,
	   not by GCC itself.

       -mfix-vr4130
	   Work around the VR4130 "mflo"/"mfhi" errata.	 The workarounds are
	   implemented by the assembler rather than by GCC, although GCC
	   avoids using "mflo" and "mfhi" if the VR4130 "macc", "macchi",
	   "dmacc" and "dmacchi" instructions are available instead.

       -mfix-sb1
       -mno-fix-sb1
	   Work around certain SB-1 CPU core errata.  (This flag currently
	   works around the SB-1 revision 2 "F1" and "F2" floating-point
	   errata.)

       -mr10k-cache-barrier=setting
	   Specify whether GCC should insert cache barriers to avoid the side-
	   effects of speculation on R10K processors.

	   In common with many processors, the R10K tries to predict the
	   outcome of a conditional branch and speculatively executes
	   instructions from the "taken" branch.  It later aborts these
	   instructions if the predicted outcome is wrong.  However, on the
	   R10K, even aborted instructions can have side effects.

	   This problem only affects kernel stores and, depending on the
	   system, kernel loads.  As an example, a speculatively-executed
	   store may load the target memory into cache and mark the cache line
	   as dirty, even if the store itself is later aborted.	 If a DMA
	   operation writes to the same area of memory before the "dirty" line
	   is flushed, the cached data overwrites the DMA-ed data.  See the
	   R10K processor manual for a full description, including other
	   potential problems.

	   One workaround is to insert cache barrier instructions before every
	   memory access that might be speculatively executed and that might
	   have side effects even if aborted.  -mr10k-cache-barrier=setting
	   controls GCC's implementation of this workaround.  It assumes that
	   aborted accesses to any byte in the following regions does not have
	   side effects:

	   1.  the memory occupied by the current function's stack frame;

	   2.  the memory occupied by an incoming stack argument;

	   3.  the memory occupied by an object with a link-time-constant
	       address.

	   It is the kernel's responsibility to ensure that speculative
	   accesses to these regions are indeed safe.

	   If the input program contains a function declaration such as:

		   void foo (void);

	   then the implementation of "foo" must allow "j foo" and "jal foo"
	   to be executed speculatively.  GCC honors this restriction for
	   functions it compiles itself.  It expects non-GCC functions (such
	   as hand-written assembly code) to do the same.

	   The option has three forms:

	   -mr10k-cache-barrier=load-store
	       Insert a cache barrier before a load or store that might be
	       speculatively executed and that might have side effects even if
	       aborted.

	   -mr10k-cache-barrier=store
	       Insert a cache barrier before a store that might be
	       speculatively executed and that might have side effects even if
	       aborted.

	   -mr10k-cache-barrier=none
	       Disable the insertion of cache barriers.	 This is the default
	       setting.

       -mflush-func=func
       -mno-flush-func
	   Specifies the function to call to flush the I and D caches, or to
	   not call any such function.	If called, the function must take the
	   same arguments as the common "_flush_func()", that is, the address
	   of the memory range for which the cache is being flushed, the size
	   of the memory range, and the number 3 (to flush both caches).  The
	   default depends on the target GCC was configured for, but commonly
	   is either _flush_func or __cpu_flush.

       mbranch-cost=num
	   Set the cost of branches to roughly num "simple" instructions.
	   This cost is only a heuristic and is not guaranteed to produce
	   consistent results across releases.	A zero cost redundantly
	   selects the default, which is based on the -mtune setting.

       -mbranch-likely
       -mno-branch-likely
	   Enable or disable use of Branch Likely instructions, regardless of
	   the default for the selected architecture.  By default, Branch
	   Likely instructions may be generated if they are supported by the
	   selected architecture.  An exception is for the MIPS32 and MIPS64
	   architectures and processors that implement those architectures;
	   for those, Branch Likely instructions are not be generated by
	   default because the MIPS32 and MIPS64 architectures specifically
	   deprecate their use.

       -mfp-exceptions
       -mno-fp-exceptions
	   Specifies whether FP exceptions are enabled.	 This affects how FP
	   instructions are scheduled for some processors.  The default is
	   that FP exceptions are enabled.

	   For instance, on the SB-1, if FP exceptions are disabled, and we
	   are emitting 64-bit code, then we can use both FP pipes.
	   Otherwise, we can only use one FP pipe.

       -mvr4130-align
       -mno-vr4130-align
	   The VR4130 pipeline is two-way superscalar, but can only issue two
	   instructions together if the first one is 8-byte aligned.  When
	   this option is enabled, GCC aligns pairs of instructions that it
	   thinks should execute in parallel.

	   This option only has an effect when optimizing for the VR4130.  It
	   normally makes code faster, but at the expense of making it bigger.
	   It is enabled by default at optimization level -O3.

       -msynci
       -mno-synci
	   Enable (disable) generation of "synci" instructions on
	   architectures that support it.  The "synci" instructions (if
	   enabled) are generated when "__builtin___clear_cache()" is
	   compiled.

	   This option defaults to "-mno-synci", but the default can be
	   overridden by configuring with "--with-synci".

	   When compiling code for single processor systems, it is generally
	   safe to use "synci".	 However, on many multi-core (SMP) systems, it
	   does not invalidate the instruction caches on all cores and may
	   lead to undefined behavior.

       -mrelax-pic-calls
       -mno-relax-pic-calls
	   Try to turn PIC calls that are normally dispatched via register $25
	   into direct calls.  This is only possible if the linker can resolve
	   the destination at link-time and if the destination is within range
	   for a direct call.

	   -mrelax-pic-calls is the default if GCC was configured to use an
	   assembler and a linker that support the ".reloc" assembly directive
	   and "-mexplicit-relocs" is in effect.  With "-mno-explicit-relocs",
	   this optimization can be performed by the assembler and the linker
	   alone without help from the compiler.

       -mmcount-ra-address
       -mno-mcount-ra-address
	   Emit (do not emit) code that allows "_mcount" to modify the calling
	   function's return address.  When enabled, this option extends the
	   usual "_mcount" interface with a new ra-address parameter, which
	   has type "intptr_t *" and is passed in register $12.	 "_mcount" can
	   then modify the return address by doing both of the following:

	   o   Returning the new address in register $31.

	   o   Storing the new address in "*ra-address", if ra-address is
	       nonnull.

	   The default is -mno-mcount-ra-address.

   MMIX Options
       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
	   Specify that intrinsic library functions are being compiled,
	   passing all values in registers, no matter the size.

       -mepsilon
       -mno-epsilon
	   Generate floating-point comparison instructions that compare with
	   respect to the "rE" epsilon register.

       -mabi=mmixware
       -mabi=gnu
	   Generate code that passes function parameters and return values
	   that (in the called function) are seen as registers $0 and up, as
	   opposed to the GNU ABI which uses global registers $231 and up.

       -mzero-extend
       -mno-zero-extend
	   When reading data from memory in sizes shorter than 64 bits, use
	   (do not use) zero-extending load instructions by default, rather
	   than sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
	   Make the result of a division yielding a remainder have the same
	   sign as the divisor.	 With the default, -mno-knuthdiv, the sign of
	   the remainder follows the sign of the dividend.  Both methods are
	   arithmetically valid, the latter being almost exclusively used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
	   Prepend (do not prepend) a : to all global symbols, so the assembly
	   code can be used with the "PREFIX" assembly directive.

       -melf
	   Generate an executable in the ELF format, rather than the default
	   mmo format used by the mmix simulator.

       -mbranch-predict
       -mno-branch-predict
	   Use (do not use) the probable-branch instructions, when static
	   branch prediction indicates a probable branch.

       -mbase-addresses
       -mno-base-addresses
	   Generate (do not generate) code that uses base addresses.  Using a
	   base address automatically generates a request (handled by the
	   assembler and the linker) for a constant to be set up in a global
	   register.  The register is used for one or more base address
	   requests within the range 0 to 255 from the value held in the
	   register.  The generally leads to short and fast code, but the
	   number of different data items that can be addressed is limited.
	   This means that a program that uses lots of static data may require
	   -mno-base-addresses.

       -msingle-exit
       -mno-single-exit
	   Force (do not force) generated code to have a single exit point in
	   each function.

   MN10300 Options
       These -m options are defined for Matsushita MN10300 architectures:

       -mmult-bug
	   Generate code to avoid bugs in the multiply instructions for the
	   MN10300 processors.	This is the default.

       -mno-mult-bug
	   Do not generate code to avoid bugs in the multiply instructions for
	   the MN10300 processors.

       -mam33
	   Generate code using features specific to the AM33 processor.

       -mno-am33
	   Do not generate code using features specific to the AM33 processor.
	   This is the default.

       -mam33-2
	   Generate code using features specific to the AM33/2.0 processor.

       -mam34
	   Generate code using features specific to the AM34 processor.

       -mtune=cpu-type
	   Use the timing characteristics of the indicated CPU type when
	   scheduling instructions.  This does not change the targeted
	   processor type.  The CPU type must be one of mn10300, am33, am33-2
	   or am34.

       -mreturn-pointer-on-d0
	   When generating a function that returns a pointer, return the
	   pointer in both "a0" and "d0".  Otherwise, the pointer is returned
	   only in "a0", and attempts to call such functions without a
	   prototype result in errors.	Note that this option is on by
	   default; use -mno-return-pointer-on-d0 to disable it.

       -mno-crt0
	   Do not link in the C run-time initialization object file.

       -mrelax
	   Indicate to the linker that it should perform a relaxation
	   optimization pass to shorten branches, calls and absolute memory
	   addresses.  This option only has an effect when used on the command
	   line for the final link step.

	   This option makes symbolic debugging impossible.

       -mliw
	   Allow the compiler to generate Long Instruction Word instructions
	   if the target is the AM33 or later.	This is the default.  This
	   option defines the preprocessor macro __LIW__.

       -mnoliw
	   Do not allow the compiler to generate Long Instruction Word
	   instructions.  This option defines the preprocessor macro
	   __NO_LIW__.

       -msetlb
	   Allow the compiler to generate the SETLB and Lcc instructions if
	   the target is the AM33 or later.  This is the default.  This option
	   defines the preprocessor macro __SETLB__.

       -mnosetlb
	   Do not allow the compiler to generate SETLB or Lcc instructions.
	   This option defines the preprocessor macro __NO_SETLB__.

   Moxie Options
       -meb
	   Generate big-endian code.  This is the default for moxie-*-*
	   configurations.

       -mel
	   Generate little-endian code.

       -mno-crt0
	   Do not link in the C run-time initialization object file.

   PDP-11 Options
       These options are defined for the PDP-11:

       -mfpu
	   Use hardware FPP floating point.  This is the default.  (FIS
	   floating point on the PDP-11/40 is not supported.)

       -msoft-float
	   Do not use hardware floating point.

       -mac0
	   Return floating-point results in ac0 (fr0 in Unix assembler
	   syntax).

       -mno-ac0
	   Return floating-point results in memory.  This is the default.

       -m40
	   Generate code for a PDP-11/40.

       -m45
	   Generate code for a PDP-11/45.  This is the default.

       -m10
	   Generate code for a PDP-11/10.

       -mbcopy-builtin
	   Use inline "movmemhi" patterns for copying memory.  This is the
	   default.

       -mbcopy
	   Do not use inline "movmemhi" patterns for copying memory.

       -mint16
       -mno-int32
	   Use 16-bit "int".  This is the default.

       -mint32
       -mno-int16
	   Use 32-bit "int".

       -mfloat64
       -mno-float32
	   Use 64-bit "float".	This is the default.

       -mfloat32
       -mno-float64
	   Use 32-bit "float".

       -mabshi
	   Use "abshi2" pattern.  This is the default.

       -mno-abshi
	   Do not use "abshi2" pattern.

       -mbranch-expensive
	   Pretend that branches are expensive.	 This is for experimenting
	   with code generation only.

       -mbranch-cheap
	   Do not pretend that branches are expensive.	This is the default.

       -munix-asm
	   Use Unix assembler syntax.  This is the default when configured for
	   pdp11-*-bsd.

       -mdec-asm
	   Use DEC assembler syntax.  This is the default when configured for
	   any PDP-11 target other than pdp11-*-bsd.

   picoChip Options
       These -m options are defined for picoChip implementations:

       -mae=ae_type
	   Set the instruction set, register set, and instruction scheduling
	   parameters for array element type ae_type.  Supported values for
	   ae_type are ANY, MUL, and MAC.

	   -mae=ANY selects a completely generic AE type.  Code generated with
	   this option runs on any of the other AE types.  The code is not as
	   efficient as it would be if compiled for a specific AE type, and
	   some types of operation (e.g., multiplication) do not work properly
	   on all types of AE.

	   -mae=MUL selects a MUL AE type.  This is the most useful AE type
	   for compiled code, and is the default.

	   -mae=MAC selects a DSP-style MAC AE.	 Code compiled with this
	   option may suffer from poor performance of byte (char)
	   manipulation, since the DSP AE does not provide hardware support
	   for byte load/stores.

       -msymbol-as-address
	   Enable the compiler to directly use a symbol name as an address in
	   a load/store instruction, without first loading it into a register.
	   Typically, the use of this option generates larger programs, which
	   run faster than when the option isn't used.	However, the results
	   vary from program to program, so it is left as a user option,
	   rather than being permanently enabled.

       -mno-inefficient-warnings
	   Disables warnings about the generation of inefficient code.	These
	   warnings can be generated, for example, when compiling code that
	   performs byte-level memory operations on the MAC AE type.  The MAC
	   AE has no hardware support for byte-level memory operations, so all
	   byte load/stores must be synthesized from word load/store
	   operations.	This is inefficient and a warning is generated to
	   indicate that you should rewrite the code to avoid byte operations,
	   or to target an AE type that has the necessary hardware support.
	   This option disables these warnings.

   PowerPC Options
       These are listed under

   RL78 Options
       -msim
	   Links in additional target libraries to support operation within a
	   simulator.

       -mmul=none
       -mmul=g13
       -mmul=rl78
	   Specifies the type of hardware multiplication support to be used.
	   The default is "none", which uses software multiplication
	   functions.  The "g13" option is for the hardware multiply/divide
	   peripheral only on the RL78/G13 targets.  The "rl78" option is for
	   the standard hardware multiplication defined in the RL78 software
	   manual.

   IBM RS/6000 and PowerPC Options
       These -m options are defined for the IBM RS/6000 and PowerPC:

       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
       -mmfcrf
       -mno-mfcrf
       -mpopcntb
       -mno-popcntb
       -mpopcntd
       -mno-popcntd
       -mfprnd
       -mno-fprnd
       -mcmpb
       -mno-cmpb
       -mmfpgpr
       -mno-mfpgpr
       -mhard-dfp
       -mno-hard-dfp
	   You use these options to specify which instructions are available
	   on the processor you are using.  The default value of these options
	   is determined when configuring GCC.	Specifying the -mcpu=cpu_type
	   overrides the specification of these options.  We recommend you use
	   the -mcpu=cpu_type option rather than the options listed above.

	   Specifying -mpowerpc-gpopt allows GCC to use the optional PowerPC
	   architecture instructions in the General Purpose group, including
	   floating-point square root.	Specifying -mpowerpc-gfxopt allows GCC
	   to use the optional PowerPC architecture instructions in the
	   Graphics group, including floating-point select.

	   The -mmfcrf option allows GCC to generate the move from condition
	   register field instruction implemented on the POWER4 processor and
	   other processors that support the PowerPC V2.01 architecture.  The
	   -mpopcntb option allows GCC to generate the popcount and double-
	   precision FP reciprocal estimate instruction implemented on the
	   POWER5 processor and other processors that support the PowerPC
	   V2.02 architecture.	The -mpopcntd option allows GCC to generate
	   the popcount instruction implemented on the POWER7 processor and
	   other processors that support the PowerPC V2.06 architecture.  The
	   -mfprnd option allows GCC to generate the FP round to integer
	   instructions implemented on the POWER5+ processor and other
	   processors that support the PowerPC V2.03 architecture.  The -mcmpb
	   option allows GCC to generate the compare bytes instruction
	   implemented on the POWER6 processor and other processors that
	   support the PowerPC V2.05 architecture.  The -mmfpgpr option allows
	   GCC to generate the FP move to/from general-purpose register
	   instructions implemented on the POWER6X processor and other
	   processors that support the extended PowerPC V2.05 architecture.
	   The -mhard-dfp option allows GCC to generate the decimal floating-
	   point instructions implemented on some POWER processors.

	   The -mpowerpc64 option allows GCC to generate the additional 64-bit
	   instructions that are found in the full PowerPC64 architecture and
	   to treat GPRs as 64-bit, doubleword quantities.  GCC defaults to
	   -mno-powerpc64.

       -mcpu=cpu_type
	   Set architecture type, register usage, and instruction scheduling
	   parameters for machine type cpu_type.  Supported values for
	   cpu_type are 401, 403, 405, 405fp, 440, 440fp, 464, 464fp, 476,
	   476fp, 505, 601, 602, 603, 603e, 604, 604e, 620, 630, 740, 7400,
	   7450, 750, 801, 821, 823, 860, 970, 8540, a2, e300c2, e300c3,
	   e500mc, e500mc64, e5500, e6500, ec603e, G3, G4, G5, titan, power3,
	   power4, power5, power5+, power6, power6x, power7, power8, powerpc,
	   powerpc64, and rs64.

	   -mcpu=powerpc, and -mcpu=powerpc64 specify pure 32-bit PowerPC and
	   64-bit PowerPC architecture machine types, with an appropriate,
	   generic processor model assumed for scheduling purposes.

	   The other options specify a specific processor.  Code generated
	   under those options runs best on that processor, and may not run at
	   all on others.

	   The -mcpu options automatically enable or disable the following
	   options:

	   -maltivec  -mfprnd  -mhard-float  -mmfcrf  -mmultiple -mpopcntb
	   -mpopcntd  -mpowerpc64 -mpowerpc-gpopt  -mpowerpc-gfxopt
	   -msingle-float -mdouble-float -msimple-fpu -mstring	-mmulhw
	   -mdlmzb  -mmfpgpr -mvsx -mcrypto -mdirect-move -mpower8-fusion
	   -mpower8-vector -mquad-memory -mquad-memory-atomic

	   The particular options set for any particular CPU varies between
	   compiler versions, depending on what setting seems to produce
	   optimal code for that CPU; it doesn't necessarily reflect the
	   actual hardware's capabilities.  If you wish to set an individual
	   option to a particular value, you may specify it after the -mcpu
	   option, like -mcpu=970 -mno-altivec.

	   On AIX, the -maltivec and -mpowerpc64 options are not enabled or
	   disabled by the -mcpu option at present because AIX does not have
	   full support for these options.  You may still enable or disable
	   them individually if you're sure it'll work in your environment.

       -mtune=cpu_type
	   Set the instruction scheduling parameters for machine type
	   cpu_type, but do not set the architecture type or register usage,
	   as -mcpu=cpu_type does.  The same values for cpu_type are used for
	   -mtune as for -mcpu.	 If both are specified, the code generated
	   uses the architecture and registers set by -mcpu, but the
	   scheduling parameters set by -mtune.

       -mcmodel=small
	   Generate PowerPC64 code for the small model: The TOC is limited to
	   64k.

       -mcmodel=medium
	   Generate PowerPC64 code for the medium model: The TOC and other
	   static data may be up to a total of 4G in size.

       -mcmodel=large
	   Generate PowerPC64 code for the large model: The TOC may be up to
	   4G in size.	Other data and code is only limited by the 64-bit
	   address space.

       -maltivec
       -mno-altivec
	   Generate code that uses (does not use) AltiVec instructions, and
	   also enable the use of built-in functions that allow more direct
	   access to the AltiVec instruction set.  You may also need to set
	   -mabi=altivec to adjust the current ABI with AltiVec ABI
	   enhancements.

	   When -maltivec is used, rather than -maltivec=le or -maltivec=be,
	   the element order for Altivec intrinsics such as "vec_splat",
	   "vec_extract", and "vec_insert" will match array element order
	   corresponding to the endianness of the target.  That is, element
	   zero identifies the leftmost element in a vector register when
	   targeting a big-endian platform, and identifies the rightmost
	   element in a vector register when targeting a little-endian
	   platform.

       -maltivec=be
	   Generate Altivec instructions using big-endian element order,
	   regardless of whether the target is big- or little-endian.  This is
	   the default when targeting a big-endian platform.

	   The element order is used to interpret element numbers in Altivec
	   intrinsics such as "vec_splat", "vec_extract", and "vec_insert".
	   By default, these will match array element order corresponding to
	   the endianness for the target.

       -maltivec=le
	   Generate Altivec instructions using little-endian element order,
	   regardless of whether the target is big- or little-endian.  This is
	   the default when targeting a little-endian platform.	 This option
	   is currently ignored when targeting a big-endian platform.

	   The element order is used to interpret element numbers in Altivec
	   intrinsics such as "vec_splat", "vec_extract", and "vec_insert".
	   By default, these will match array element order corresponding to
	   the endianness for the target.

       -mvrsave
       -mno-vrsave
	   Generate VRSAVE instructions when generating AltiVec code.

       -mgen-cell-microcode
	   Generate Cell microcode instructions.

       -mwarn-cell-microcode
	   Warn when a Cell microcode instruction is emitted.  An example of a
	   Cell microcode instruction is a variable shift.

       -msecure-plt
	   Generate code that allows ld and ld.so to build executables and
	   shared libraries with non-executable ".plt" and ".got" sections.
	   This is a PowerPC 32-bit SYSV ABI option.

       -mbss-plt
	   Generate code that uses a BSS ".plt" section that ld.so fills in,
	   and requires ".plt" and ".got" sections that are both writable and
	   executable.	This is a PowerPC 32-bit SYSV ABI option.

       -misel
       -mno-isel
	   This switch enables or disables the generation of ISEL
	   instructions.

       -misel=yes/no
	   This switch has been deprecated.  Use -misel and -mno-isel instead.

       -mspe
       -mno-spe
	   This switch enables or disables the generation of SPE simd
	   instructions.

       -mpaired
       -mno-paired
	   This switch enables or disables the generation of PAIRED simd
	   instructions.

       -mspe=yes/no
	   This option has been deprecated.  Use -mspe and -mno-spe instead.

       -mvsx
       -mno-vsx
	   Generate code that uses (does not use) vector/scalar (VSX)
	   instructions, and also enable the use of built-in functions that
	   allow more direct access to the VSX instruction set.

       -mcrypto
       -mno-crypto
	   Enable the use (disable) of the built-in functions that allow
	   direct access to the cryptographic instructions that were added in
	   version 2.07 of the PowerPC ISA.

       -mdirect-move
       -mno-direct-move
	   Generate code that uses (does not use) the instructions to move
	   data between the general purpose registers and the vector/scalar
	   (VSX) registers that were added in version 2.07 of the PowerPC ISA.

       -mpower8-fusion
       -mno-power8-fusion
	   Generate code that keeps (does not keeps) some integer operations
	   adjacent so that the instructions can be fused together on power8
	   and later processors.

       -mpower8-vector
       -mno-power8-vector
	   Generate code that uses (does not use) the vector and scalar
	   instructions that were added in version 2.07 of the PowerPC ISA.
	   Also enable the use of built-in functions that allow more direct
	   access to the vector instructions.

       -mquad-memory
       -mno-quad-memory
	   Generate code that uses (does not use) the non-atomic quad word
	   memory instructions.	 The -mquad-memory option requires use of
	   64-bit mode.

       -mquad-memory-atomic
       -mno-quad-memory-atomic
	   Generate code that uses (does not use) the atomic quad word memory
	   instructions.  The -mquad-memory-atomic option requires use of
	   64-bit mode.

       -mfloat-gprs=yes/single/double/no
       -mfloat-gprs
	   This switch enables or disables the generation of floating-point
	   operations on the general-purpose registers for architectures that
	   support it.

	   The argument yes or single enables the use of single-precision
	   floating-point operations.

	   The argument double enables the use of single and double-precision
	   floating-point operations.

	   The argument no disables floating-point operations on the general-
	   purpose registers.

	   This option is currently only available on the MPC854x.

       -m32
       -m64
	   Generate code for 32-bit or 64-bit environments of Darwin and SVR4
	   targets (including GNU/Linux).  The 32-bit environment sets int,
	   long and pointer to 32 bits and generates code that runs on any
	   PowerPC variant.  The 64-bit environment sets int to 32 bits and
	   long and pointer to 64 bits, and generates code for PowerPC64, as
	   for -mpowerpc64.

       -mfull-toc
       -mno-fp-in-toc
       -mno-sum-in-toc
       -mminimal-toc
	   Modify generation of the TOC (Table Of Contents), which is created
	   for every executable file.  The -mfull-toc option is selected by
	   default.  In that case, GCC allocates at least one TOC entry for
	   each unique non-automatic variable reference in your program.  GCC
	   also places floating-point constants in the TOC.  However, only
	   16,384 entries are available in the TOC.

	   If you receive a linker error message that saying you have
	   overflowed the available TOC space, you can reduce the amount of
	   TOC space used with the -mno-fp-in-toc and -mno-sum-in-toc options.
	   -mno-fp-in-toc prevents GCC from putting floating-point constants
	   in the TOC and -mno-sum-in-toc forces GCC to generate code to
	   calculate the sum of an address and a constant at run time instead
	   of putting that sum into the TOC.  You may specify one or both of
	   these options.  Each causes GCC to produce very slightly slower and
	   larger code at the expense of conserving TOC space.

	   If you still run out of space in the TOC even when you specify both
	   of these options, specify -mminimal-toc instead.  This option
	   causes GCC to make only one TOC entry for every file.  When you
	   specify this option, GCC produces code that is slower and larger
	   but which uses extremely little TOC space.  You may wish to use
	   this option only on files that contain less frequently-executed
	   code.

       -maix64
       -maix32
	   Enable 64-bit AIX ABI and calling convention: 64-bit pointers,
	   64-bit "long" type, and the infrastructure needed to support them.
	   Specifying -maix64 implies -mpowerpc64, while -maix32 disables the
	   64-bit ABI and implies -mno-powerpc64.  GCC defaults to -maix32.

       -mxl-compat
       -mno-xl-compat
	   Produce code that conforms more closely to IBM XL compiler
	   semantics when using AIX-compatible ABI.  Pass floating-point
	   arguments to prototyped functions beyond the register save area
	   (RSA) on the stack in addition to argument FPRs.  Do not assume
	   that most significant double in 128-bit long double value is
	   properly rounded when comparing values and converting to double.
	   Use XL symbol names for long double support routines.

	   The AIX calling convention was extended but not initially
	   documented to handle an obscure K&R C case of calling a function
	   that takes the address of its arguments with fewer arguments than
	   declared.  IBM XL compilers access floating-point arguments that do
	   not fit in the RSA from the stack when a subroutine is compiled
	   without optimization.  Because always storing floating-point
	   arguments on the stack is inefficient and rarely needed, this
	   option is not enabled by default and only is necessary when calling
	   subroutines compiled by IBM XL compilers without optimization.

       -mpe
	   Support IBM RS/6000 SP Parallel Environment (PE).  Link an
	   application written to use message passing with special startup
	   code to enable the application to run.  The system must have PE
	   installed in the standard location (/usr/lpp/ppe.poe/), or the
	   specs file must be overridden with the -specs= option to specify
	   the appropriate directory location.	The Parallel Environment does
	   not support threads, so the -mpe option and the -pthread option are
	   incompatible.

       -malign-natural
       -malign-power
	   On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option
	   -malign-natural overrides the ABI-defined alignment of larger
	   types, such as floating-point doubles, on their natural size-based
	   boundary.  The option -malign-power instructs GCC to follow the
	   ABI-specified alignment rules.  GCC defaults to the standard
	   alignment defined in the ABI.

	   On 64-bit Darwin, natural alignment is the default, and
	   -malign-power is not supported.

       -msoft-float
       -mhard-float
	   Generate code that does not use (uses) the floating-point register
	   set.	 Software floating-point emulation is provided if you use the
	   -msoft-float option, and pass the option to GCC when linking.

       -msingle-float
       -mdouble-float
	   Generate code for single- or double-precision floating-point
	   operations.	-mdouble-float implies -msingle-float.

       -msimple-fpu
	   Do not generate "sqrt" and "div" instructions for hardware
	   floating-point unit.

       -mfpu=name
	   Specify type of floating-point unit.	 Valid values for name are
	   sp_lite (equivalent to -msingle-float -msimple-fpu), dp_lite
	   (equivalent to -mdouble-float -msimple-fpu), sp_full (equivalent to
	   -msingle-float), and dp_full (equivalent to -mdouble-float).

       -mxilinx-fpu
	   Perform optimizations for the floating-point unit on Xilinx PPC
	   405/440.

       -mmultiple
       -mno-multiple
	   Generate code that uses (does not use) the load multiple word
	   instructions and the store multiple word instructions.  These
	   instructions are generated by default on POWER systems, and not
	   generated on PowerPC systems.  Do not use -mmultiple on little-
	   endian PowerPC systems, since those instructions do not work when
	   the processor is in little-endian mode.  The exceptions are PPC740
	   and PPC750 which permit these instructions in little-endian mode.

       -mstring
       -mno-string
	   Generate code that uses (does not use) the load string instructions
	   and the store string word instructions to save multiple registers
	   and do small block moves.  These instructions are generated by
	   default on POWER systems, and not generated on PowerPC systems.  Do
	   not use -mstring on little-endian PowerPC systems, since those
	   instructions do not work when the processor is in little-endian
	   mode.  The exceptions are PPC740 and PPC750 which permit these
	   instructions in little-endian mode.

       -mupdate
       -mno-update
	   Generate code that uses (does not use) the load or store
	   instructions that update the base register to the address of the
	   calculated memory location.	These instructions are generated by
	   default.  If you use -mno-update, there is a small window between
	   the time that the stack pointer is updated and the address of the
	   previous frame is stored, which means code that walks the stack
	   frame across interrupts or signals may get corrupted data.

       -mavoid-indexed-addresses
       -mno-avoid-indexed-addresses
	   Generate code that tries to avoid (not avoid) the use of indexed
	   load or store instructions. These instructions can incur a
	   performance penalty on Power6 processors in certain situations,
	   such as when stepping through large arrays that cross a 16M
	   boundary.  This option is enabled by default when targeting Power6
	   and disabled otherwise.

       -mfused-madd
       -mno-fused-madd
	   Generate code that uses (does not use) the floating-point multiply
	   and accumulate instructions.	 These instructions are generated by
	   default if hardware floating point is used.	The machine-dependent
	   -mfused-madd option is now mapped to the machine-independent
	   -ffp-contract=fast option, and -mno-fused-madd is mapped to
	   -ffp-contract=off.

       -mmulhw
       -mno-mulhw
	   Generate code that uses (does not use) the half-word multiply and
	   multiply-accumulate instructions on the IBM 405, 440, 464 and 476
	   processors.	These instructions are generated by default when
	   targeting those processors.

       -mdlmzb
       -mno-dlmzb
	   Generate code that uses (does not use) the string-search dlmzb
	   instruction on the IBM 405, 440, 464 and 476 processors.  This
	   instruction is generated by default when targeting those
	   processors.

       -mno-bit-align
       -mbit-align
	   On System V.4 and embedded PowerPC systems do not (do) force
	   structures and unions that contain bit-fields to be aligned to the
	   base type of the bit-field.

	   For example, by default a structure containing nothing but 8
	   "unsigned" bit-fields of length 1 is aligned to a 4-byte boundary
	   and has a size of 4 bytes.  By using -mno-bit-align, the structure
	   is aligned to a 1-byte boundary and is 1 byte in size.

       -mno-strict-align
       -mstrict-align
	   On System V.4 and embedded PowerPC systems do not (do) assume that
	   unaligned memory references are handled by the system.

       -mrelocatable
       -mno-relocatable
	   Generate code that allows (does not allow) a static executable to
	   be relocated to a different address at run time.  A simple embedded
	   PowerPC system loader should relocate the entire contents of
	   ".got2" and 4-byte locations listed in the ".fixup" section, a
	   table of 32-bit addresses generated by this option.	For this to
	   work, all objects linked together must be compiled with
	   -mrelocatable or -mrelocatable-lib.	-mrelocatable code aligns the
	   stack to an 8-byte boundary.

       -mrelocatable-lib
       -mno-relocatable-lib
	   Like -mrelocatable, -mrelocatable-lib generates a ".fixup" section
	   to allow static executables to be relocated at run time, but
	   -mrelocatable-lib does not use the smaller stack alignment of
	   -mrelocatable.  Objects compiled with -mrelocatable-lib may be
	   linked with objects compiled with any combination of the
	   -mrelocatable options.

       -mno-toc
       -mtoc
	   On System V.4 and embedded PowerPC systems do not (do) assume that
	   register 2 contains a pointer to a global area pointing to the
	   addresses used in the program.

       -mlittle
       -mlittle-endian
	   On System V.4 and embedded PowerPC systems compile code for the
	   processor in little-endian mode.  The -mlittle-endian option is the
	   same as -mlittle.

       -mbig
       -mbig-endian
	   On System V.4 and embedded PowerPC systems compile code for the
	   processor in big-endian mode.  The -mbig-endian option is the same
	   as -mbig.

       -mdynamic-no-pic
	   On Darwin and Mac OS X systems, compile code so that it is not
	   relocatable, but that its external references are relocatable.  The
	   resulting code is suitable for applications, but not shared
	   libraries.

       -msingle-pic-base
	   Treat the register used for PIC addressing as read-only, rather
	   than loading it in the prologue for each function.  The runtime
	   system is responsible for initializing this register with an
	   appropriate value before execution begins.

       -mprioritize-restricted-insns=priority
	   This option controls the priority that is assigned to dispatch-slot
	   restricted instructions during the second scheduling pass.  The
	   argument priority takes the value 0, 1, or 2 to assign no, highest,
	   or second-highest (respectively) priority to dispatch-slot
	   restricted instructions.

       -msched-costly-dep=dependence_type
	   This option controls which dependences are considered costly by the
	   target during instruction scheduling.  The argument dependence_type
	   takes one of the following values:

	   no  No dependence is costly.

	   all All dependences are costly.

	   true_store_to_load
	       A true dependence from store to load is costly.

	   store_to_load
	       Any dependence from store to load is costly.

	   number
	       Any dependence for which the latency is greater than or equal
	       to number is costly.

       -minsert-sched-nops=scheme
	   This option controls which NOP insertion scheme is used during the
	   second scheduling pass.  The argument scheme takes one of the
	   following values:

	   no  Don't insert NOPs.

	   pad Pad with NOPs any dispatch group that has vacant issue slots,
	       according to the scheduler's grouping.

	   regroup_exact
	       Insert NOPs to force costly dependent insns into separate
	       groups.	Insert exactly as many NOPs as needed to force an insn
	       to a new group, according to the estimated processor grouping.

	   number
	       Insert NOPs to force costly dependent insns into separate
	       groups.	Insert number NOPs to force an insn to a new group.

       -mcall-sysv
	   On System V.4 and embedded PowerPC systems compile code using
	   calling conventions that adhere to the March 1995 draft of the
	   System V Application Binary Interface, PowerPC processor
	   supplement.	This is the default unless you configured GCC using
	   powerpc-*-eabiaix.

       -mcall-sysv-eabi
       -mcall-eabi
	   Specify both -mcall-sysv and -meabi options.

       -mcall-sysv-noeabi
	   Specify both -mcall-sysv and -mno-eabi options.

       -mcall-aixdesc
	   On System V.4 and embedded PowerPC systems compile code for the AIX
	   operating system.

       -mcall-linux
	   On System V.4 and embedded PowerPC systems compile code for the
	   Linux-based GNU system.

       -mcall-freebsd
	   On System V.4 and embedded PowerPC systems compile code for the
	   FreeBSD operating system.

       -mcall-netbsd
	   On System V.4 and embedded PowerPC systems compile code for the
	   NetBSD operating system.

       -mcall-openbsd
	   On System V.4 and embedded PowerPC systems compile code for the
	   OpenBSD operating system.

       -maix-struct-return
	   Return all structures in memory (as specified by the AIX ABI).

       -msvr4-struct-return
	   Return structures smaller than 8 bytes in registers (as specified
	   by the SVR4 ABI).

       -mabi=abi-type
	   Extend the current ABI with a particular extension, or remove such
	   extension.  Valid values are altivec, no-altivec, spe, no-spe,
	   ibmlongdouble, ieeelongdouble, elfv1, elfv2.

       -mabi=spe
	   Extend the current ABI with SPE ABI extensions.  This does not
	   change the default ABI, instead it adds the SPE ABI extensions to
	   the current ABI.

       -mabi=no-spe
	   Disable Book-E SPE ABI extensions for the current ABI.

       -mabi=ibmlongdouble
	   Change the current ABI to use IBM extended-precision long double.
	   This is a PowerPC 32-bit SYSV ABI option.

       -mabi=ieeelongdouble
	   Change the current ABI to use IEEE extended-precision long double.
	   This is a PowerPC 32-bit Linux ABI option.

       -mabi=elfv1
	   Change the current ABI to use the ELFv1 ABI.	 This is the default
	   ABI for big-endian PowerPC 64-bit Linux.  Overriding the default
	   ABI requires special system support and is likely to fail in
	   spectacular ways.

       -mabi=elfv2
	   Change the current ABI to use the ELFv2 ABI.	 This is the default
	   ABI for little-endian PowerPC 64-bit Linux.	Overriding the default
	   ABI requires special system support and is likely to fail in
	   spectacular ways.

       -mprototype
       -mno-prototype
	   On System V.4 and embedded PowerPC systems assume that all calls to
	   variable argument functions are properly prototyped.	 Otherwise,
	   the compiler must insert an instruction before every non-prototyped
	   call to set or clear bit 6 of the condition code register (CR) to
	   indicate whether floating-point values are passed in the floating-
	   point registers in case the function takes variable arguments.
	   With -mprototype, only calls to prototyped variable argument
	   functions set or clear the bit.

       -msim
	   On embedded PowerPC systems, assume that the startup module is
	   called sim-crt0.o and that the standard C libraries are libsim.a
	   and libc.a.	This is the default for powerpc-*-eabisim
	   configurations.

       -mmvme
	   On embedded PowerPC systems, assume that the startup module is
	   called crt0.o and the standard C libraries are libmvme.a and
	   libc.a.

       -mads
	   On embedded PowerPC systems, assume that the startup module is
	   called crt0.o and the standard C libraries are libads.a and libc.a.

       -myellowknife
	   On embedded PowerPC systems, assume that the startup module is
	   called crt0.o and the standard C libraries are libyk.a and libc.a.

       -mvxworks
	   On System V.4 and embedded PowerPC systems, specify that you are
	   compiling for a VxWorks system.

       -memb
	   On embedded PowerPC systems, set the PPC_EMB bit in the ELF flags
	   header to indicate that eabi extended relocations are used.

       -meabi
       -mno-eabi
	   On System V.4 and embedded PowerPC systems do (do not) adhere to
	   the Embedded Applications Binary Interface (EABI), which is a set
	   of modifications to the System V.4 specifications.  Selecting
	   -meabi means that the stack is aligned to an 8-byte boundary, a
	   function "__eabi" is called from "main" to set up the EABI
	   environment, and the -msdata option can use both "r2" and "r13" to
	   point to two separate small data areas.  Selecting -mno-eabi means
	   that the stack is aligned to a 16-byte boundary, no EABI
	   initialization function is called from "main", and the -msdata
	   option only uses "r13" to point to a single small data area.	 The
	   -meabi option is on by default if you configured GCC using one of
	   the powerpc*-*-eabi* options.

       -msdata=eabi
	   On System V.4 and embedded PowerPC systems, put small initialized
	   "const" global and static data in the .sdata2 section, which is
	   pointed to by register "r2".	 Put small initialized non-"const"
	   global and static data in the .sdata section, which is pointed to
	   by register "r13".  Put small uninitialized global and static data
	   in the .sbss section, which is adjacent to the .sdata section.  The
	   -msdata=eabi option is incompatible with the -mrelocatable option.
	   The -msdata=eabi option also sets the -memb option.

       -msdata=sysv
	   On System V.4 and embedded PowerPC systems, put small global and
	   static data in the .sdata section, which is pointed to by register
	   "r13".  Put small uninitialized global and static data in the .sbss
	   section, which is adjacent to the .sdata section.  The -msdata=sysv
	   option is incompatible with the -mrelocatable option.

       -msdata=default
       -msdata
	   On System V.4 and embedded PowerPC systems, if -meabi is used,
	   compile code the same as -msdata=eabi, otherwise compile code the
	   same as -msdata=sysv.

       -msdata=data
	   On System V.4 and embedded PowerPC systems, put small global data
	   in the .sdata section.  Put small uninitialized global data in the
	   .sbss section.  Do not use register "r13" to address small data
	   however.  This is the default behavior unless other -msdata options
	   are used.

       -msdata=none
       -mno-sdata
	   On embedded PowerPC systems, put all initialized global and static
	   data in the .data section, and all uninitialized data in the .bss
	   section.

       -mblock-move-inline-limit=num
	   Inline all block moves (such as calls to "memcpy" or structure
	   copies) less than or equal to num bytes.  The minimum value for num
	   is 32 bytes on 32-bit targets and 64 bytes on 64-bit targets.  The
	   default value is target-specific.

       -G num
	   On embedded PowerPC systems, put global and static items less than
	   or equal to num bytes into the small data or BSS sections instead
	   of the normal data or BSS section.  By default, num is 8.  The -G
	   num switch is also passed to the linker.  All modules should be
	   compiled with the same -G num value.

       -mregnames
       -mno-regnames
	   On System V.4 and embedded PowerPC systems do (do not) emit
	   register names in the assembly language output using symbolic
	   forms.

       -mlongcall
       -mno-longcall
	   By default assume that all calls are far away so that a longer and
	   more expensive calling sequence is required.	 This is required for
	   calls farther than 32 megabytes (33,554,432 bytes) from the current
	   location.  A short call is generated if the compiler knows the call
	   cannot be that far away.  This setting can be overridden by the
	   "shortcall" function attribute, or by "#pragma longcall(0)".

	   Some linkers are capable of detecting out-of-range calls and
	   generating glue code on the fly.  On these systems, long calls are
	   unnecessary and generate slower code.  As of this writing, the AIX
	   linker can do this, as can the GNU linker for PowerPC/64.  It is
	   planned to add this feature to the GNU linker for 32-bit PowerPC
	   systems as well.

	   On Darwin/PPC systems, "#pragma longcall" generates "jbsr callee,
	   L42", plus a branch island (glue code).  The two target addresses
	   represent the callee and the branch island.	The Darwin/PPC linker
	   prefers the first address and generates a "bl callee" if the PPC
	   "bl" instruction reaches the callee directly; otherwise, the linker
	   generates "bl L42" to call the branch island.  The branch island is
	   appended to the body of the calling function; it computes the full
	   32-bit address of the callee and jumps to it.

	   On Mach-O (Darwin) systems, this option directs the compiler emit
	   to the glue for every direct call, and the Darwin linker decides
	   whether to use or discard it.

	   In the future, GCC may ignore all longcall specifications when the
	   linker is known to generate glue.

       -mtls-markers
       -mno-tls-markers
	   Mark (do not mark) calls to "__tls_get_addr" with a relocation
	   specifying the function argument.  The relocation allows the linker
	   to reliably associate function call with argument setup
	   instructions for TLS optimization, which in turn allows GCC to
	   better schedule the sequence.

       -pthread
	   Adds support for multithreading with the pthreads library.  This
	   option sets flags for both the preprocessor and linker.

       -mrecip
       -mno-recip
	   This option enables use of the reciprocal estimate and reciprocal
	   square root estimate instructions with additional Newton-Raphson
	   steps to increase precision instead of doing a divide or square
	   root and divide for floating-point arguments.  You should use the
	   -ffast-math option when using -mrecip (or at least
	   -funsafe-math-optimizations, -finite-math-only, -freciprocal-math
	   and -fno-trapping-math).  Note that while the throughput of the
	   sequence is generally higher than the throughput of the non-
	   reciprocal instruction, the precision of the sequence can be
	   decreased by up to 2 ulp (i.e. the inverse of 1.0 equals
	   0.99999994) for reciprocal square roots.

       -mrecip=opt
	   This option controls which reciprocal estimate instructions may be
	   used.  opt is a comma-separated list of options, which may be
	   preceded by a "!" to invert the option: "all": enable all estimate
	   instructions, "default": enable the default instructions,
	   equivalent to -mrecip, "none": disable all estimate instructions,
	   equivalent to -mno-recip; "div": enable the reciprocal
	   approximation instructions for both single and double precision;
	   "divf": enable the single-precision reciprocal approximation
	   instructions; "divd": enable the double-precision reciprocal
	   approximation instructions; "rsqrt": enable the reciprocal square
	   root approximation instructions for both single and double
	   precision; "rsqrtf": enable the single-precision reciprocal square
	   root approximation instructions; "rsqrtd": enable the double-
	   precision reciprocal square root approximation instructions;

	   So, for example, -mrecip=all,!rsqrtd enables all of the reciprocal
	   estimate instructions, except for the "FRSQRTE", "XSRSQRTEDP", and
	   "XVRSQRTEDP" instructions which handle the double-precision
	   reciprocal square root calculations.

       -mrecip-precision
       -mno-recip-precision
	   Assume (do not assume) that the reciprocal estimate instructions
	   provide higher-precision estimates than is mandated by the PowerPC
	   ABI.	 Selecting -mcpu=power6, -mcpu=power7 or -mcpu=power8
	   automatically selects -mrecip-precision.  The double-precision
	   square root estimate instructions are not generated by default on
	   low-precision machines, since they do not provide an estimate that
	   converges after three steps.

       -mveclibabi=type
	   Specifies the ABI type to use for vectorizing intrinsics using an
	   external library.  The only type supported at present is "mass",
	   which specifies to use IBM's Mathematical Acceleration Subsystem
	   (MASS) libraries for vectorizing intrinsics using external
	   libraries.  GCC currently emits calls to "acosd2", "acosf4",
	   "acoshd2", "acoshf4", "asind2", "asinf4", "asinhd2", "asinhf4",
	   "atan2d2", "atan2f4", "atand2", "atanf4", "atanhd2", "atanhf4",
	   "cbrtd2", "cbrtf4", "cosd2", "cosf4", "coshd2", "coshf4", "erfcd2",
	   "erfcf4", "erfd2", "erff4", "exp2d2", "exp2f4", "expd2", "expf4",
	   "expm1d2", "expm1f4", "hypotd2", "hypotf4", "lgammad2", "lgammaf4",
	   "log10d2", "log10f4", "log1pd2", "log1pf4", "log2d2", "log2f4",
	   "logd2", "logf4", "powd2", "powf4", "sind2", "sinf4", "sinhd2",
	   "sinhf4", "sqrtd2", "sqrtf4", "tand2", "tanf4", "tanhd2", and
	   "tanhf4" when generating code for power7.  Both -ftree-vectorize
	   and -funsafe-math-optimizations must also be enabled.  The MASS
	   libraries must be specified at link time.

       -mfriz
       -mno-friz
	   Generate (do not generate) the "friz" instruction when the
	   -funsafe-math-optimizations option is used to optimize rounding of
	   floating-point values to 64-bit integer and back to floating point.
	   The "friz" instruction does not return the same value if the
	   floating-point number is too large to fit in an integer.

       -mpointers-to-nested-functions
       -mno-pointers-to-nested-functions
	   Generate (do not generate) code to load up the static chain
	   register (r11) when calling through a pointer on AIX and 64-bit
	   Linux systems where a function pointer points to a 3-word
	   descriptor giving the function address, TOC value to be loaded in
	   register r2, and static chain value to be loaded in register r11.
	   The -mpointers-to-nested-functions is on by default.	 You cannot
	   call through pointers to nested functions or pointers to functions
	   compiled in other languages that use the static chain if you use
	   the -mno-pointers-to-nested-functions.

       -msave-toc-indirect
       -mno-save-toc-indirect
	   Generate (do not generate) code to save the TOC value in the
	   reserved stack location in the function prologue if the function
	   calls through a pointer on AIX and 64-bit Linux systems.  If the
	   TOC value is not saved in the prologue, it is saved just before the
	   call through the pointer.  The -mno-save-toc-indirect option is the
	   default.

       -mcompat-align-parm
       -mno-compat-align-parm
	   Generate (do not generate) code to pass structure parameters with a
	   maximum alignment of 64 bits, for compatibility with older versions
	   of GCC.

	   Older versions of GCC (prior to 4.9.0) incorrectly did not align a
	   structure parameter on a 128-bit boundary when that structure
	   contained a member requiring 128-bit alignment.  This is corrected
	   in more recent versions of GCC.  This option may be used to
	   generate code that is compatible with functions compiled with older
	   versions of GCC.

	   In this version of the compiler, the -mcompat-align-parm is the
	   default, except when using the Linux ELFv2 ABI.

   RX Options
       These command-line options are defined for RX targets:

       -m64bit-doubles
       -m32bit-doubles
	   Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits
	   (-m32bit-doubles) in size.  The default is -m32bit-doubles.	Note
	   RX floating-point hardware only works on 32-bit values, which is
	   why the default is -m32bit-doubles.

       -fpu
       -nofpu
	   Enables (-fpu) or disables (-nofpu) the use of RX floating-point
	   hardware.  The default is enabled for the RX600 series and disabled
	   for the RX200 series.

	   Floating-point instructions are only generated for 32-bit floating-
	   point values, however, so the FPU hardware is not used for doubles
	   if the -m64bit-doubles option is used.

	   Note If the -fpu option is enabled then -funsafe-math-optimizations
	   is also enabled automatically.  This is because the RX FPU
	   instructions are themselves unsafe.

       -mcpu=name
	   Selects the type of RX CPU to be targeted.  Currently three types
	   are supported, the generic RX600 and RX200 series hardware and the
	   specific RX610 CPU.	The default is RX600.

	   The only difference between RX600 and RX610 is that the RX610 does
	   not support the "MVTIPL" instruction.

	   The RX200 series does not have a hardware floating-point unit and
	   so -nofpu is enabled by default when this type is selected.

       -mbig-endian-data
       -mlittle-endian-data
	   Store data (but not code) in the big-endian format.	The default is
	   -mlittle-endian-data, i.e. to store data in the little-endian
	   format.

       -msmall-data-limit=N
	   Specifies the maximum size in bytes of global and static variables
	   which can be placed into the small data area.  Using the small data
	   area can lead to smaller and faster code, but the size of area is
	   limited and it is up to the programmer to ensure that the area does
	   not overflow.  Also when the small data area is used one of the
	   RX's registers (usually "r13") is reserved for use pointing to this
	   area, so it is no longer available for use by the compiler.	This
	   could result in slower and/or larger code if variables are pushed
	   onto the stack instead of being held in this register.

	   Note, common variables (variables that have not been initialized)
	   and constants are not placed into the small data area as they are
	   assigned to other sections in the output executable.

	   The default value is zero, which disables this feature.  Note, this
	   feature is not enabled by default with higher optimization levels
	   (-O2 etc) because of the potentially detrimental effects of
	   reserving a register.  It is up to the programmer to experiment and
	   discover whether this feature is of benefit to their program.  See
	   the description of the -mpid option for a description of how the
	   actual register to hold the small data area pointer is chosen.

       -msim
       -mno-sim
	   Use the simulator runtime.  The default is to use the libgloss
	   board-specific runtime.

       -mas100-syntax
       -mno-as100-syntax
	   When generating assembler output use a syntax that is compatible
	   with Renesas's AS100 assembler.  This syntax can also be handled by
	   the GAS assembler, but it has some restrictions so it is not
	   generated by default.

       -mmax-constant-size=N
	   Specifies the maximum size, in bytes, of a constant that can be
	   used as an operand in a RX instruction.  Although the RX
	   instruction set does allow constants of up to 4 bytes in length to
	   be used in instructions, a longer value equates to a longer
	   instruction.	 Thus in some circumstances it can be beneficial to
	   restrict the size of constants that are used in instructions.
	   Constants that are too big are instead placed into a constant pool
	   and referenced via register indirection.

	   The value N can be between 0 and 4.	A value of 0 (the default) or
	   4 means that constants of any size are allowed.

       -mrelax
	   Enable linker relaxation.  Linker relaxation is a process whereby
	   the linker attempts to reduce the size of a program by finding
	   shorter versions of various instructions.  Disabled by default.

       -mint-register=N
	   Specify the number of registers to reserve for fast interrupt
	   handler functions.  The value N can be between 0 and 4.  A value of
	   1 means that register "r13" is reserved for the exclusive use of
	   fast interrupt handlers.  A value of 2 reserves "r13" and "r12".  A
	   value of 3 reserves "r13", "r12" and "r11", and a value of 4
	   reserves "r13" through "r10".  A value of 0, the default, does not
	   reserve any registers.

       -msave-acc-in-interrupts
	   Specifies that interrupt handler functions should preserve the
	   accumulator register.  This is only necessary if normal code might
	   use the accumulator register, for example because it performs
	   64-bit multiplications.  The default is to ignore the accumulator
	   as this makes the interrupt handlers faster.

       -mpid
       -mno-pid
	   Enables the generation of position independent data.	 When enabled
	   any access to constant data is done via an offset from a base
	   address held in a register.	This allows the location of constant
	   data to be determined at run time without requiring the executable
	   to be relocated, which is a benefit to embedded applications with
	   tight memory constraints.  Data that can be modified is not
	   affected by this option.

	   Note, using this feature reserves a register, usually "r13", for
	   the constant data base address.  This can result in slower and/or
	   larger code, especially in complicated functions.

	   The actual register chosen to hold the constant data base address
	   depends upon whether the -msmall-data-limit and/or the
	   -mint-register command-line options are enabled.  Starting with
	   register "r13" and proceeding downwards, registers are allocated
	   first to satisfy the requirements of -mint-register, then -mpid and
	   finally -msmall-data-limit.	Thus it is possible for the small data
	   area register to be "r8" if both -mint-register=4 and -mpid are
	   specified on the command line.

	   By default this feature is not enabled.  The default can be
	   restored via the -mno-pid command-line option.

       -mno-warn-multiple-fast-interrupts
       -mwarn-multiple-fast-interrupts
	   Prevents GCC from issuing a warning message if it finds more than
	   one fast interrupt handler when it is compiling a file.  The
	   default is to issue a warning for each extra fast interrupt handler
	   found, as the RX only supports one such interrupt.

       Note: The generic GCC command-line option -ffixed-reg has special
       significance to the RX port when used with the "interrupt" function
       attribute.  This attribute indicates a function intended to process
       fast interrupts.	 GCC ensures that it only uses the registers "r10",
       "r11", "r12" and/or "r13" and only provided that the normal use of the
       corresponding registers have been restricted via the -ffixed-reg or
       -mint-register command-line options.

   S/390 and zSeries Options
       These are the -m options defined for the S/390 and zSeries
       architecture.

       -mhard-float
       -msoft-float
	   Use (do not use) the hardware floating-point instructions and
	   registers for floating-point operations.  When -msoft-float is
	   specified, functions in libgcc.a are used to perform floating-point
	   operations.	When -mhard-float is specified, the compiler generates
	   IEEE floating-point instructions.  This is the default.

       -mhard-dfp
       -mno-hard-dfp
	   Use (do not use) the hardware decimal-floating-point instructions
	   for decimal-floating-point operations.  When -mno-hard-dfp is
	   specified, functions in libgcc.a are used to perform decimal-
	   floating-point operations.  When -mhard-dfp is specified, the
	   compiler generates decimal-floating-point hardware instructions.
	   This is the default for -march=z9-ec or higher.

       -mlong-double-64
       -mlong-double-128
	   These switches control the size of "long double" type. A size of 64
	   bits makes the "long double" type equivalent to the "double" type.
	   This is the default.

       -mbackchain
       -mno-backchain
	   Store (do not store) the address of the caller's frame as backchain
	   pointer into the callee's stack frame.  A backchain may be needed
	   to allow debugging using tools that do not understand DWARF 2 call
	   frame information.  When -mno-packed-stack is in effect, the
	   backchain pointer is stored at the bottom of the stack frame; when
	   -mpacked-stack is in effect, the backchain is placed into the
	   topmost word of the 96/160 byte register save area.

	   In general, code compiled with -mbackchain is call-compatible with
	   code compiled with -mmo-backchain; however, use of the backchain
	   for debugging purposes usually requires that the whole binary is
	   built with -mbackchain.  Note that the combination of -mbackchain,
	   -mpacked-stack and -mhard-float is not supported.  In order to
	   build a linux kernel use -msoft-float.

	   The default is to not maintain the backchain.

       -mpacked-stack
       -mno-packed-stack
	   Use (do not use) the packed stack layout.  When -mno-packed-stack
	   is specified, the compiler uses the all fields of the 96/160 byte
	   register save area only for their default purpose; unused fields
	   still take up stack space.  When -mpacked-stack is specified,
	   register save slots are densely packed at the top of the register
	   save area; unused space is reused for other purposes, allowing for
	   more efficient use of the available stack space.  However, when
	   -mbackchain is also in effect, the topmost word of the save area is
	   always used to store the backchain, and the return address register
	   is always saved two words below the backchain.

	   As long as the stack frame backchain is not used, code generated
	   with -mpacked-stack is call-compatible with code generated with
	   -mno-packed-stack.  Note that some non-FSF releases of GCC 2.95 for
	   S/390 or zSeries generated code that uses the stack frame backchain
	   at run time, not just for debugging purposes.  Such code is not
	   call-compatible with code compiled with -mpacked-stack.  Also, note
	   that the combination of -mbackchain, -mpacked-stack and
	   -mhard-float is not supported.  In order to build a linux kernel
	   use -msoft-float.

	   The default is to not use the packed stack layout.

       -msmall-exec
       -mno-small-exec
	   Generate (or do not generate) code using the "bras" instruction to
	   do subroutine calls.	 This only works reliably if the total
	   executable size does not exceed 64k.	 The default is to use the
	   "basr" instruction instead, which does not have this limitation.

       -m64
       -m31
	   When -m31 is specified, generate code compliant to the GNU/Linux
	   for S/390 ABI.  When -m64 is specified, generate code compliant to
	   the GNU/Linux for zSeries ABI.  This allows GCC in particular to
	   generate 64-bit instructions.  For the s390 targets, the default is
	   -m31, while the s390x targets default to -m64.

       -mzarch
       -mesa
	   When -mzarch is specified, generate code using the instructions
	   available on z/Architecture.	 When -mesa is specified, generate
	   code using the instructions available on ESA/390.  Note that -mesa
	   is not possible with -m64.  When generating code compliant to the
	   GNU/Linux for S/390 ABI, the default is -mesa.  When generating
	   code compliant to the GNU/Linux for zSeries ABI, the default is
	   -mzarch.

       -mmvcle
       -mno-mvcle
	   Generate (or do not generate) code using the "mvcle" instruction to
	   perform block moves.	 When -mno-mvcle is specified, use a "mvc"
	   loop instead.  This is the default unless optimizing for size.

       -mdebug
       -mno-debug
	   Print (or do not print) additional debug information when
	   compiling.  The default is to not print debug information.

       -march=cpu-type
	   Generate code that runs on cpu-type, which is the name of a system
	   representing a certain processor type.  Possible values for cpu-
	   type are g5, g6, z900, z990, z9-109, z9-ec and z10.	When
	   generating code using the instructions available on z/Architecture,
	   the default is -march=z900.	Otherwise, the default is -march=g5.

       -mtune=cpu-type
	   Tune to cpu-type everything applicable about the generated code,
	   except for the ABI and the set of available instructions.  The list
	   of cpu-type values is the same as for -march.  The default is the
	   value used for -march.

       -mtpf-trace
       -mno-tpf-trace
	   Generate code that adds (does not add) in TPF OS specific branches
	   to trace routines in the operating system.  This option is off by
	   default, even when compiling for the TPF OS.

       -mfused-madd
       -mno-fused-madd
	   Generate code that uses (does not use) the floating-point multiply
	   and accumulate instructions.	 These instructions are generated by
	   default if hardware floating point is used.

       -mwarn-framesize=framesize
	   Emit a warning if the current function exceeds the given frame
	   size.  Because this is a compile-time check it doesn't need to be a
	   real problem when the program runs.	It is intended to identify
	   functions that most probably cause a stack overflow.	 It is useful
	   to be used in an environment with limited stack size e.g. the linux
	   kernel.

       -mwarn-dynamicstack
	   Emit a warning if the function calls "alloca" or uses dynamically-
	   sized arrays.  This is generally a bad idea with a limited stack
	   size.

       -mstack-guard=stack-guard
       -mstack-size=stack-size
	   If these options are provided the S/390 back end emits additional
	   instructions in the function prologue that trigger a trap if the
	   stack size is stack-guard bytes above the stack-size (remember that
	   the stack on S/390 grows downward).	If the stack-guard option is
	   omitted the smallest power of 2 larger than the frame size of the
	   compiled function is chosen.	 These options are intended to be used
	   to help debugging stack overflow problems.  The additionally
	   emitted code causes only little overhead and hence can also be used
	   in production-like systems without greater performance degradation.
	   The given values have to be exact powers of 2 and stack-size has to
	   be greater than stack-guard without exceeding 64k.  In order to be
	   efficient the extra code makes the assumption that the stack starts
	   at an address aligned to the value given by stack-size.  The stack-
	   guard option can only be used in conjunction with stack-size.

       -mhotpatch[=halfwords]
       -mno-hotpatch
	   If the hotpatch option is enabled, a "hot-patching" function
	   prologue is generated for all functions in the compilation unit.
	   The funtion label is prepended with the given number of two-byte
	   Nop instructions (halfwords, maximum 1000000) or 12 Nop
	   instructions if no argument is present.  Functions with a hot-
	   patching prologue are never inlined automatically, and a hot-
	   patching prologue is never generated for functions functions that
	   are explicitly inline.

	   This option can be overridden for individual functions with the
	   "hotpatch" attribute.

   Score Options
       These options are defined for Score implementations:

       -meb
	   Compile code for big-endian mode.  This is the default.

       -mel
	   Compile code for little-endian mode.

       -mnhwloop
	   Disable generation of "bcnz" instructions.

       -muls
	   Enable generation of unaligned load and store instructions.

       -mmac
	   Enable the use of multiply-accumulate instructions. Disabled by
	   default.

       -mscore5
	   Specify the SCORE5 as the target architecture.

       -mscore5u
	   Specify the SCORE5U of the target architecture.

       -mscore7
	   Specify the SCORE7 as the target architecture. This is the default.

       -mscore7d
	   Specify the SCORE7D as the target architecture.

   SH Options
       These -m options are defined for the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m2e
	   Generate code for the SH2e.

       -m2a-nofpu
	   Generate code for the SH2a without FPU, or for a SH2a-FPU in such a
	   way that the floating-point unit is not used.

       -m2a-single-only
	   Generate code for the SH2a-FPU, in such a way that no double-
	   precision floating-point operations are used.

       -m2a-single
	   Generate code for the SH2a-FPU assuming the floating-point unit is
	   in single-precision mode by default.

       -m2a
	   Generate code for the SH2a-FPU assuming the floating-point unit is
	   in double-precision mode by default.

       -m3 Generate code for the SH3.

       -m3e
	   Generate code for the SH3e.

       -m4-nofpu
	   Generate code for the SH4 without a floating-point unit.

       -m4-single-only
	   Generate code for the SH4 with a floating-point unit that only
	   supports single-precision arithmetic.

       -m4-single
	   Generate code for the SH4 assuming the floating-point unit is in
	   single-precision mode by default.

       -m4 Generate code for the SH4.

       -m4-100
	   Generate code for SH4-100.

       -m4-100-nofpu
	   Generate code for SH4-100 in such a way that the floating-point
	   unit is not used.

       -m4-100-single
	   Generate code for SH4-100 assuming the floating-point unit is in
	   single-precision mode by default.

       -m4-100-single-only
	   Generate code for SH4-100 in such a way that no double-precision
	   floating-point operations are used.

       -m4-200
	   Generate code for SH4-200.

       -m4-200-nofpu
	   Generate code for SH4-200 without in such a way that the floating-
	   point unit is not used.

       -m4-200-single
	   Generate code for SH4-200 assuming the floating-point unit is in
	   single-precision mode by default.

       -m4-200-single-only
	   Generate code for SH4-200 in such a way that no double-precision
	   floating-point operations are used.

       -m4-300
	   Generate code for SH4-300.

       -m4-300-nofpu
	   Generate code for SH4-300 without in such a way that the floating-
	   point unit is not used.

       -m4-300-single
	   Generate code for SH4-300 in such a way that no double-precision
	   floating-point operations are used.

       -m4-300-single-only
	   Generate code for SH4-300 in such a way that no double-precision
	   floating-point operations are used.

       -m4-340
	   Generate code for SH4-340 (no MMU, no FPU).

       -m4-500
	   Generate code for SH4-500 (no FPU).	Passes -isa=sh4-nofpu to the
	   assembler.

       -m4a-nofpu
	   Generate code for the SH4al-dsp, or for a SH4a in such a way that
	   the floating-point unit is not used.

       -m4a-single-only
	   Generate code for the SH4a, in such a way that no double-precision
	   floating-point operations are used.

       -m4a-single
	   Generate code for the SH4a assuming the floating-point unit is in
	   single-precision mode by default.

       -m4a
	   Generate code for the SH4a.

       -m4al
	   Same as -m4a-nofpu, except that it implicitly passes -dsp to the
	   assembler.  GCC doesn't generate any DSP instructions at the
	   moment.

       -m5-32media
	   Generate 32-bit code for SHmedia.

       -m5-32media-nofpu
	   Generate 32-bit code for SHmedia in such a way that the floating-
	   point unit is not used.

       -m5-64media
	   Generate 64-bit code for SHmedia.

       -m5-64media-nofpu
	   Generate 64-bit code for SHmedia in such a way that the floating-
	   point unit is not used.

       -m5-compact
	   Generate code for SHcompact.

       -m5-compact-nofpu
	   Generate code for SHcompact in such a way that the floating-point
	   unit is not used.

       -mb Compile code for the processor in big-endian mode.

       -ml Compile code for the processor in little-endian mode.

       -mdalign
	   Align doubles at 64-bit boundaries.	Note that this changes the
	   calling conventions, and thus some functions from the standard C
	   library do not work unless you recompile it first with -mdalign.

       -mrelax
	   Shorten some address references at link time, when possible; uses
	   the linker option -relax.

       -mbigtable
	   Use 32-bit offsets in "switch" tables.  The default is to use
	   16-bit offsets.

       -mbitops
	   Enable the use of bit manipulation instructions on SH2A.

       -mfmovd
	   Enable the use of the instruction "fmovd".  Check -mdalign for
	   alignment constraints.

       -mrenesas
	   Comply with the calling conventions defined by Renesas.

       -mno-renesas
	   Comply with the calling conventions defined for GCC before the
	   Renesas conventions were available.	This option is the default for
	   all targets of the SH toolchain.

       -mnomacsave
	   Mark the "MAC" register as call-clobbered, even if -mrenesas is
	   given.

       -mieee
       -mno-ieee
	   Control the IEEE compliance of floating-point comparisons, which
	   affects the handling of cases where the result of a comparison is
	   unordered.  By default -mieee is implicitly enabled.	 If
	   -ffinite-math-only is enabled -mno-ieee is implicitly set, which
	   results in faster floating-point greater-equal and less-equal
	   comparisons.	 The implcit settings can be overridden by specifying
	   either -mieee or -mno-ieee.

       -minline-ic_invalidate
	   Inline code to invalidate instruction cache entries after setting
	   up nested function trampolines.  This option has no effect if
	   -musermode is in effect and the selected code generation option
	   (e.g. -m4) does not allow the use of the "icbi" instruction.	 If
	   the selected code generation option does not allow the use of the
	   "icbi" instruction, and -musermode is not in effect, the inlined
	   code manipulates the instruction cache address array directly with
	   an associative write.  This not only requires privileged mode at
	   run time, but it also fails if the cache line had been mapped via
	   the TLB and has become unmapped.

       -misize
	   Dump instruction size and location in the assembly code.

       -mpadstruct
	   This option is deprecated.  It pads structures to multiple of 4
	   bytes, which is incompatible with the SH ABI.

       -matomic-model=model
	   Sets the model of atomic operations and additional parameters as a
	   comma separated list.  For details on the atomic built-in functions
	   see __atomic Builtins.  The following models and parameters are
	   supported:

	   none
	       Disable compiler generated atomic sequences and emit library
	       calls for atomic operations.  This is the default if the target
	       is not "sh*-*-linux*".

	   soft-gusa
	       Generate GNU/Linux compatible gUSA software atomic sequences
	       for the atomic built-in functions.  The generated atomic
	       sequences require additional support from the
	       interrupt/exception handling code of the system and are only
	       suitable for SH3* and SH4* single-core systems.	This option is
	       enabled by default when the target is "sh*-*-linux*" and SH3*
	       or SH4*.	 When the target is SH4A, this option will also
	       partially utilize the hardware atomic instructions "movli.l"
	       and "movco.l" to create more efficient code, unless strict is
	       specified.

	   soft-tcb
	       Generate software atomic sequences that use a variable in the
	       thread control block.  This is a variation of the gUSA
	       sequences which can also be used on SH1* and SH2* targets.  The
	       generated atomic sequences require additional support from the
	       interrupt/exception handling code of the system and are only
	       suitable for single-core systems.  When using this model, the
	       gbr-offset= parameter has to be specified as well.

	   soft-imask
	       Generate software atomic sequences that temporarily disable
	       interrupts by setting "SR.IMASK = 1111".	 This model works only
	       when the program runs in privileged mode and is only suitable
	       for single-core systems.	 Additional support from the
	       interrupt/exception handling code of the system is not
	       required.  This model is enabled by default when the target is
	       "sh*-*-linux*" and SH1* or SH2*.

	   hard-llcs
	       Generate hardware atomic sequences using the "movli.l" and
	       "movco.l" instructions only.  This is only available on SH4A
	       and is suitable for multi-core systems.	Since the hardware
	       instructions support only 32 bit atomic variables access to 8
	       or 16 bit variables is emulated with 32 bit accesses.  Code
	       compiled with this option will also be compatible with other
	       software atomic model interrupt/exception handling systems if
	       executed on an SH4A system.  Additional support from the
	       interrupt/exception handling code of the system is not required
	       for this model.

	   gbr-offset=
	       This parameter specifies the offset in bytes of the variable in
	       the thread control block structure that should be used by the
	       generated atomic sequences when the soft-tcb model has been
	       selected.  For other models this parameter is ignored.  The
	       specified value must be an integer multiple of four and in the
	       range 0-1020.

	   strict
	       This parameter prevents mixed usage of multiple atomic models,
	       even though they would be compatible, and will make the
	       compiler generate atomic sequences of the specified model only.

       -mtas
	   Generate the "tas.b" opcode for "__atomic_test_and_set".  Notice
	   that depending on the particular hardware and software
	   configuration this can degrade overall performance due to the
	   operand cache line flushes that are implied by the "tas.b"
	   instruction.	 On multi-core SH4A processors the "tas.b" instruction
	   must be used with caution since it can result in data corruption
	   for certain cache configurations.

       -mprefergot
	   When generating position-independent code, emit function calls
	   using the Global Offset Table instead of the Procedure Linkage
	   Table.

       -musermode
       -mno-usermode
	   Don't allow (allow) the compiler generating privileged mode code.
	   Specifying -musermode also implies -mno-inline-ic_invalidate if the
	   inlined code would not work in user mode.  -musermode is the
	   default when the target is "sh*-*-linux*".  If the target is SH1*
	   or SH2* -musermode has no effect, since there is no user mode.

       -multcost=number
	   Set the cost to assume for a multiply insn.

       -mdiv=strategy
	   Set the division strategy to be used for integer division
	   operations.	For SHmedia strategy can be one of:

	   fp  Performs the operation in floating point.  This has a very high
	       latency, but needs only a few instructions, so it might be a
	       good choice if your code has enough easily-exploitable ILP to
	       allow the compiler to schedule the floating-point instructions
	       together with other instructions.  Division by zero causes a
	       floating-point exception.

	   inv Uses integer operations to calculate the inverse of the
	       divisor, and then multiplies the dividend with the inverse.
	       This strategy allows CSE and hoisting of the inverse
	       calculation.  Division by zero calculates an unspecified
	       result, but does not trap.

	   inv:minlat
	       A variant of inv where, if no CSE or hoisting opportunities
	       have been found, or if the entire operation has been hoisted to
	       the same place, the last stages of the inverse calculation are
	       intertwined with the final multiply to reduce the overall
	       latency, at the expense of using a few more instructions, and
	       thus offering fewer scheduling opportunities with other code.

	   call
	       Calls a library function that usually implements the inv:minlat
	       strategy.  This gives high code density for "m5-*media-nofpu"
	       compilations.

	   call2
	       Uses a different entry point of the same library function,
	       where it assumes that a pointer to a lookup table has already
	       been set up, which exposes the pointer load to CSE and code
	       hoisting optimizations.

	   inv:call
	   inv:call2
	   inv:fp
	       Use the inv algorithm for initial code generation, but if the
	       code stays unoptimized, revert to the call, call2, or fp
	       strategies, respectively.  Note that the potentially-trapping
	       side effect of division by zero is carried by a separate
	       instruction, so it is possible that all the integer
	       instructions are hoisted out, but the marker for the side
	       effect stays where it is.  A recombination to floating-point
	       operations or a call is not possible in that case.

	   inv20u
	   inv20l
	       Variants of the inv:minlat strategy.  In the case that the
	       inverse calculation is not separated from the multiply, they
	       speed up division where the dividend fits into 20 bits (plus
	       sign where applicable) by inserting a test to skip a number of
	       operations in this case; this test slows down the case of
	       larger dividends.  inv20u assumes the case of a such a small
	       dividend to be unlikely, and inv20l assumes it to be likely.

	   For targets other than SHmedia strategy can be one of:

	   call-div1
	       Calls a library function that uses the single-step division
	       instruction "div1" to perform the operation.  Division by zero
	       calculates an unspecified result and does not trap.  This is
	       the default except for SH4, SH2A and SHcompact.

	   call-fp
	       Calls a library function that performs the operation in double
	       precision floating point.  Division by zero causes a floating-
	       point exception.	 This is the default for SHcompact with FPU.
	       Specifying this for targets that do not have a double precision
	       FPU will default to "call-div1".

	   call-table
	       Calls a library function that uses a lookup table for small
	       divisors and the "div1" instruction with case distinction for
	       larger divisors.	 Division by zero calculates an unspecified
	       result and does not trap.  This is the default for SH4.
	       Specifying this for targets that do not have dynamic shift
	       instructions will default to "call-div1".

	   When a division strategy has not been specified the default
	   strategy will be selected based on the current target.  For SH2A
	   the default strategy is to use the "divs" and "divu" instructions
	   instead of library function calls.

       -maccumulate-outgoing-args
	   Reserve space once for outgoing arguments in the function prologue
	   rather than around each call.  Generally beneficial for performance
	   and size.  Also needed for unwinding to avoid changing the stack
	   frame around conditional code.

       -mdivsi3_libfunc=name
	   Set the name of the library function used for 32-bit signed
	   division to name.  This only affects the name used in the call and
	   inv:call division strategies, and the compiler still expects the
	   same sets of input/output/clobbered registers as if this option
	   were not present.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.
	   A fixed register is one that the register allocator can not use.
	   This is useful when compiling kernel code.  A register range is
	   specified as two registers separated by a dash.  Multiple register
	   ranges can be specified separated by a comma.

       -mindexed-addressing
	   Enable the use of the indexed addressing mode for
	   SHmedia32/SHcompact.	 This is only safe if the hardware and/or OS
	   implement 32-bit wrap-around semantics for the indexed addressing
	   mode.  The architecture allows the implementation of processors
	   with 64-bit MMU, which the OS could use to get 32-bit addressing,
	   but since no current hardware implementation supports this or any
	   other way to make the indexed addressing mode safe to use in the
	   32-bit ABI, the default is -mno-indexed-addressing.

       -mgettrcost=number
	   Set the cost assumed for the "gettr" instruction to number.	The
	   default is 2 if -mpt-fixed is in effect, 100 otherwise.

       -mpt-fixed
	   Assume "pt*" instructions won't trap.  This generally generates
	   better-scheduled code, but is unsafe on current hardware.  The
	   current architecture definition says that "ptabs" and "ptrel" trap
	   when the target anded with 3 is 3.  This has the unintentional
	   effect of making it unsafe to schedule these instructions before a
	   branch, or hoist them out of a loop.	 For example,
	   "__do_global_ctors", a part of libgcc that runs constructors at
	   program startup, calls functions in a list which is delimited by
	   -1.	With the -mpt-fixed option, the "ptabs" is done before testing
	   against -1.	That means that all the constructors run a bit more
	   quickly, but when the loop comes to the end of the list, the
	   program crashes because "ptabs" loads -1 into a target register.

	   Since this option is unsafe for any hardware implementing the
	   current architecture specification, the default is -mno-pt-fixed.
	   Unless specified explicitly with -mgettrcost, -mno-pt-fixed also
	   implies -mgettrcost=100; this deters register allocation from using
	   target registers for storing ordinary integers.

       -minvalid-symbols
	   Assume symbols might be invalid.  Ordinary function symbols
	   generated by the compiler are always valid to load with
	   "movi"/"shori"/"ptabs" or "movi"/"shori"/"ptrel", but with
	   assembler and/or linker tricks it is possible to generate symbols
	   that cause "ptabs" or "ptrel" to trap.  This option is only
	   meaningful when -mno-pt-fixed is in effect.	It prevents cross-
	   basic-block CSE, hoisting and most scheduling of symbol loads.  The
	   default is -mno-invalid-symbols.

       -mbranch-cost=num
	   Assume num to be the cost for a branch instruction.	Higher numbers
	   make the compiler try to generate more branch-free code if
	   possible.  If not specified the value is selected depending on the
	   processor type that is being compiled for.

       -mzdcbranch
       -mno-zdcbranch
	   Assume (do not assume) that zero displacement conditional branch
	   instructions "bt" and "bf" are fast.	 If -mzdcbranch is specified,
	   the compiler will try to prefer zero displacement branch code
	   sequences.  This is enabled by default when generating code for SH4
	   and SH4A.  It can be explicitly disabled by specifying
	   -mno-zdcbranch.

       -mcbranchdi
	   Enable the "cbranchdi4" instruction pattern.

       -mcmpeqdi
	   Emit the "cmpeqdi_t" instruction pattern even when -mcbranchdi is
	   in effect.

       -mfused-madd
       -mno-fused-madd
	   Generate code that uses (does not use) the floating-point multiply
	   and accumulate instructions.	 These instructions are generated by
	   default if hardware floating point is used.	The machine-dependent
	   -mfused-madd option is now mapped to the machine-independent
	   -ffp-contract=fast option, and -mno-fused-madd is mapped to
	   -ffp-contract=off.

       -mfsca
       -mno-fsca
	   Allow or disallow the compiler to emit the "fsca" instruction for
	   sine and cosine approximations.  The option "-mfsca" must be used
	   in combination with "-funsafe-math-optimizations".  It is enabled
	   by default when generating code for SH4A.  Using "-mno-fsca"
	   disables sine and cosine approximations even if
	   "-funsafe-math-optimizations" is in effect.

       -mfsrra
       -mno-fsrra
	   Allow or disallow the compiler to emit the "fsrra" instruction for
	   reciprocal square root approximations.  The option "-mfsrra" must
	   be used in combination with "-funsafe-math-optimizations" and
	   "-ffinite-math-only".  It is enabled by default when generating
	   code for SH4A.  Using "-mno-fsrra" disables reciprocal square root
	   approximations even if "-funsafe-math-optimizations" and
	   "-ffinite-math-only" are in effect.

       -mpretend-cmove
	   Prefer zero-displacement conditional branches for conditional move
	   instruction patterns.  This can result in faster code on the SH4
	   processor.

   Solaris 2 Options
       These -m options are supported on Solaris 2:

       -mimpure-text
	   -mimpure-text, used in addition to -shared, tells the compiler to
	   not pass -z text to the linker when linking a shared object.	 Using
	   this option, you can link position-dependent code into a shared
	   object.

	   -mimpure-text suppresses the "relocations remain against
	   allocatable but non-writable sections" linker error message.
	   However, the necessary relocations trigger copy-on-write, and the
	   shared object is not actually shared across processes.  Instead of
	   using -mimpure-text, you should compile all source code with -fpic
	   or -fPIC.

       These switches are supported in addition to the above on Solaris 2:

       -pthreads
	   Add support for multithreading using the POSIX threads library.
	   This option sets flags for both the preprocessor and linker.	 This
	   option does not affect the thread safety of object code produced
	   by the compiler or that of libraries supplied with it.

       -pthread
	   This is a synonym for -pthreads.

   SPARC Options
       These -m options are supported on the SPARC:

       -mno-app-regs
       -mapp-regs
	   Specify -mapp-regs to generate output using the global registers 2
	   through 4, which the SPARC SVR4 ABI reserves for applications.
	   Like the global register 1, each global register 2 through 4 is
	   then treated as an allocable register that is clobbered by function
	   calls.  This is the default.

	   To be fully SVR4 ABI-compliant at the cost of some performance
	   loss, specify -mno-app-regs.	 You should compile libraries and
	   system software with this option.

       -mflat
       -mno-flat
	   With -mflat, the compiler does not generate save/restore
	   instructions and uses a "flat" or single register window model.
	   This model is compatible with the regular register window model.
	   The local registers and the input registers (0--5) are still
	   treated as "call-saved" registers and are saved on the stack as
	   needed.

	   With -mno-flat (the default), the compiler generates save/restore
	   instructions (except for leaf functions).  This is the normal
	   operating mode.

       -mfpu
       -mhard-float
	   Generate output containing floating-point instructions.  This is
	   the default.

       -mno-fpu
       -msoft-float
	   Generate output containing library calls for floating point.
	   Warning: the requisite libraries are not available for all SPARC
	   targets.  Normally the facilities of the machine's usual C compiler
	   are used, but this cannot be done directly in cross-compilation.
	   You must make your own arrangements to provide suitable library
	   functions for cross-compilation.  The embedded targets sparc-*-aout
	   and sparclite-*-* do provide software floating-point support.

	   -msoft-float changes the calling convention in the output file;
	   therefore, it is only useful if you compile all of a program with
	   this option.	 In particular, you need to compile libgcc.a, the
	   library that comes with GCC, with -msoft-float in order for this to
	   work.

       -mhard-quad-float
	   Generate output containing quad-word (long double) floating-point
	   instructions.

       -msoft-quad-float
	   Generate output containing library calls for quad-word (long
	   double) floating-point instructions.	 The functions called are
	   those specified in the SPARC ABI.  This is the default.

	   As of this writing, there are no SPARC implementations that have
	   hardware support for the quad-word floating-point instructions.
	   They all invoke a trap handler for one of these instructions, and
	   then the trap handler emulates the effect of the instruction.
	   Because of the trap handler overhead, this is much slower than
	   calling the ABI library routines.  Thus the -msoft-quad-float
	   option is the default.

       -mno-unaligned-doubles
       -munaligned-doubles
	   Assume that doubles have 8-byte alignment.  This is the default.

	   With -munaligned-doubles, GCC assumes that doubles have 8-byte
	   alignment only if they are contained in another type, or if they
	   have an absolute address.  Otherwise, it assumes they have 4-byte
	   alignment.  Specifying this option avoids some rare compatibility
	   problems with code generated by other compilers.  It is not the
	   default because it results in a performance loss, especially for
	   floating-point code.

       -muser-mode
       -mno-user-mode
	   Do not generate code that can only run in supervisor mode.  This is
	   relevant only for the "casa" instruction emitted for the LEON3
	   processor.  The default is -mno-user-mode.

       -mno-faster-structs
       -mfaster-structs
	   With -mfaster-structs, the compiler assumes that structures should
	   have 8-byte alignment.  This enables the use of pairs of "ldd" and
	   "std" instructions for copies in structure assignment, in place of
	   twice as many "ld" and "st" pairs.  However, the use of this
	   changed alignment directly violates the SPARC ABI.  Thus, it's
	   intended only for use on targets where the developer acknowledges
	   that their resulting code is not directly in line with the rules of
	   the ABI.

       -mcpu=cpu_type
	   Set the instruction set, register set, and instruction scheduling
	   parameters for machine type cpu_type.  Supported values for
	   cpu_type are v7, cypress, v8, supersparc, hypersparc, leon, leon3,
	   sparclite, f930, f934, sparclite86x, sparclet, tsc701, v9,
	   ultrasparc, ultrasparc3, niagara, niagara2, niagara3 and niagara4.

	   Native Solaris and GNU/Linux toolchains also support the value
	   native, which selects the best architecture option for the host
	   processor.  -mcpu=native has no effect if GCC does not recognize
	   the processor.

	   Default instruction scheduling parameters are used for values that
	   select an architecture and not an implementation.  These are v7,
	   v8, sparclite, sparclet, v9.

	   Here is a list of each supported architecture and their supported
	   implementations.

	   v7  cypress

	   v8  supersparc, hypersparc, leon, leon3

	   sparclite
	       f930, f934, sparclite86x

	   sparclet
	       tsc701

	   v9  ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4

	   By default (unless configured otherwise), GCC generates code for
	   the V7 variant of the SPARC architecture.  With -mcpu=cypress, the
	   compiler additionally optimizes it for the Cypress CY7C602 chip, as
	   used in the SPARCStation/SPARCServer 3xx series.  This is also
	   appropriate for the older SPARCStation 1, 2, IPX etc.

	   With -mcpu=v8, GCC generates code for the V8 variant of the SPARC
	   architecture.  The only difference from V7 code is that the
	   compiler emits the integer multiply and integer divide instructions
	   which exist in SPARC-V8 but not in SPARC-V7.	 With
	   -mcpu=supersparc, the compiler additionally optimizes it for the
	   SuperSPARC chip, as used in the SPARCStation 10, 1000 and 2000
	   series.

	   With -mcpu=sparclite, GCC generates code for the SPARClite variant
	   of the SPARC architecture.  This adds the integer multiply, integer
	   divide step and scan ("ffs") instructions which exist in SPARClite
	   but not in SPARC-V7.	 With -mcpu=f930, the compiler additionally
	   optimizes it for the Fujitsu MB86930 chip, which is the original
	   SPARClite, with no FPU.  With -mcpu=f934, the compiler additionally
	   optimizes it for the Fujitsu MB86934 chip, which is the more recent
	   SPARClite with FPU.

	   With -mcpu=sparclet, GCC generates code for the SPARClet variant of
	   the SPARC architecture.  This adds the integer multiply,
	   multiply/accumulate, integer divide step and scan ("ffs")
	   instructions which exist in SPARClet but not in SPARC-V7.  With
	   -mcpu=tsc701, the compiler additionally optimizes it for the TEMIC
	   SPARClet chip.

	   With -mcpu=v9, GCC generates code for the V9 variant of the SPARC
	   architecture.  This adds 64-bit integer and floating-point move
	   instructions, 3 additional floating-point condition code registers
	   and conditional move instructions.  With -mcpu=ultrasparc, the
	   compiler additionally optimizes it for the Sun UltraSPARC I/II/IIi
	   chips.  With -mcpu=ultrasparc3, the compiler additionally optimizes
	   it for the Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+ chips.	With
	   -mcpu=niagara, the compiler additionally optimizes it for Sun
	   UltraSPARC T1 chips.	 With -mcpu=niagara2, the compiler
	   additionally optimizes it for Sun UltraSPARC T2 chips. With
	   -mcpu=niagara3, the compiler additionally optimizes it for Sun
	   UltraSPARC T3 chips.	 With -mcpu=niagara4, the compiler
	   additionally optimizes it for Sun UltraSPARC T4 chips.

       -mtune=cpu_type
	   Set the instruction scheduling parameters for machine type
	   cpu_type, but do not set the instruction set or register set that
	   the option -mcpu=cpu_type does.

	   The same values for -mcpu=cpu_type can be used for -mtune=cpu_type,
	   but the only useful values are those that select a particular CPU
	   implementation.  Those are cypress, supersparc, hypersparc, leon,
	   leon3, f930, f934, sparclite86x, tsc701, ultrasparc, ultrasparc3,
	   niagara, niagara2, niagara3 and niagara4.  With native Solaris and
	   GNU/Linux toolchains, native can also be used.

       -mv8plus
       -mno-v8plus
	   With -mv8plus, GCC generates code for the SPARC-V8+ ABI.  The
	   difference from the V8 ABI is that the global and out registers are
	   considered 64 bits wide.  This is enabled by default on Solaris in
	   32-bit mode for all SPARC-V9 processors.

       -mvis
       -mno-vis
	   With -mvis, GCC generates code that takes advantage of the
	   UltraSPARC Visual Instruction Set extensions.  The default is
	   -mno-vis.

       -mvis2
       -mno-vis2
	   With -mvis2, GCC generates code that takes advantage of version 2.0
	   of the UltraSPARC Visual Instruction Set extensions.	 The default
	   is -mvis2 when targeting a cpu that supports such instructions,
	   such as UltraSPARC-III and later.  Setting -mvis2 also sets -mvis.

       -mvis3
       -mno-vis3
	   With -mvis3, GCC generates code that takes advantage of version 3.0
	   of the UltraSPARC Visual Instruction Set extensions.	 The default
	   is -mvis3 when targeting a cpu that supports such instructions,
	   such as niagara-3 and later.	 Setting -mvis3 also sets -mvis2 and
	   -mvis.

       -mcbcond
       -mno-cbcond
	   With -mcbcond, GCC generates code that takes advantage of compare-
	   and-branch instructions, as defined in the Sparc Architecture 2011.
	   The default is -mcbcond when targeting a cpu that supports such
	   instructions, such as niagara-4 and later.

       -mpopc
       -mno-popc
	   With -mpopc, GCC generates code that takes advantage of the
	   UltraSPARC population count instruction.  The default is -mpopc
	   when targeting a cpu that supports such instructions, such as
	   Niagara-2 and later.

       -mfmaf
       -mno-fmaf
	   With -mfmaf, GCC generates code that takes advantage of the
	   UltraSPARC Fused Multiply-Add Floating-point extensions.  The
	   default is -mfmaf when targeting a cpu that supports such
	   instructions, such as Niagara-3 and later.

       -mfix-at697f
	   Enable the documented workaround for the single erratum of the
	   Atmel AT697F processor (which corresponds to erratum #13 of the
	   AT697E processor).

       -mfix-ut699
	   Enable the documented workarounds for the floating-point errata and
	   the data cache nullify errata of the UT699 processor.

       These -m options are supported in addition to the above on SPARC-V9
       processors in 64-bit environments:

       -m32
       -m64
	   Generate code for a 32-bit or 64-bit environment.  The 32-bit
	   environment sets int, long and pointer to 32 bits.  The 64-bit
	   environment sets int to 32 bits and long and pointer to 64 bits.

       -mcmodel=which
	   Set the code model to one of

	   medlow
	       The Medium/Low code model: 64-bit addresses, programs must be
	       linked in the low 32 bits of memory.  Programs can be
	       statically or dynamically linked.

	   medmid
	       The Medium/Middle code model: 64-bit addresses, programs must
	       be linked in the low 44 bits of memory, the text and data
	       segments must be less than 2GB in size and the data segment
	       must be located within 2GB of the text segment.

	   medany
	       The Medium/Anywhere code model: 64-bit addresses, programs may
	       be linked anywhere in memory, the text and data segments must
	       be less than 2GB in size and the data segment must be located
	       within 2GB of the text segment.

	   embmedany
	       The Medium/Anywhere code model for embedded systems: 64-bit
	       addresses, the text and data segments must be less than 2GB in
	       size, both starting anywhere in memory (determined at link
	       time).  The global register %g4 points to the base of the data
	       segment.	 Programs are statically linked and PIC is not
	       supported.

       -mmemory-model=mem-model
	   Set the memory model in force on the processor to one of

	   default
	       The default memory model for the processor and operating
	       system.

	   rmo Relaxed Memory Order

	   pso Partial Store Order

	   tso Total Store Order

	   sc  Sequential Consistency

	   These memory models are formally defined in Appendix D of the Sparc
	   V9 architecture manual, as set in the processor's "PSTATE.MM"
	   field.

       -mstack-bias
       -mno-stack-bias
	   With -mstack-bias, GCC assumes that the stack pointer, and frame
	   pointer if present, are offset by -2047 which must be added back
	   when making stack frame references.	This is the default in 64-bit
	   mode.  Otherwise, assume no such offset is present.

   SPU Options
       These -m options are supported on the SPU:

       -mwarn-reloc
       -merror-reloc
	   The loader for SPU does not handle dynamic relocations.  By
	   default, GCC gives an error when it generates code that requires a
	   dynamic relocation.	-mno-error-reloc disables the error,
	   -mwarn-reloc generates a warning instead.

       -msafe-dma
       -munsafe-dma
	   Instructions that initiate or test completion of DMA must not be
	   reordered with respect to loads and stores of the memory that is
	   being accessed.  With -munsafe-dma you must use the "volatile"
	   keyword to protect memory accesses, but that can lead to
	   inefficient code in places where the memory is known to not change.
	   Rather than mark the memory as volatile, you can use -msafe-dma to
	   tell the compiler to treat the DMA instructions as potentially
	   affecting all memory.

       -mbranch-hints
	   By default, GCC generates a branch hint instruction to avoid
	   pipeline stalls for always-taken or probably-taken branches.	 A
	   hint is not generated closer than 8 instructions away from its
	   branch.  There is little reason to disable them, except for
	   debugging purposes, or to make an object a little bit smaller.

       -msmall-mem
       -mlarge-mem
	   By default, GCC generates code assuming that addresses are never
	   larger than 18 bits.	 With -mlarge-mem code is generated that
	   assumes a full 32-bit address.

       -mstdmain
	   By default, GCC links against startup code that assumes the SPU-
	   style main function interface (which has an unconventional
	   parameter list).  With -mstdmain, GCC links your program against
	   startup code that assumes a C99-style interface to "main",
	   including a local copy of "argv" strings.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.
	   A fixed register is one that the register allocator cannot use.
	   This is useful when compiling kernel code.  A register range is
	   specified as two registers separated by a dash.  Multiple register
	   ranges can be specified separated by a comma.

       -mea32
       -mea64
	   Compile code assuming that pointers to the PPU address space
	   accessed via the "__ea" named address space qualifier are either 32
	   or 64 bits wide.  The default is 32 bits.  As this is an ABI-
	   changing option, all object code in an executable must be compiled
	   with the same setting.

       -maddress-space-conversion
       -mno-address-space-conversion
	   Allow/disallow treating the "__ea" address space as superset of the
	   generic address space.  This enables explicit type casts between
	   "__ea" and generic pointer as well as implicit conversions of
	   generic pointers to "__ea" pointers.	 The default is to allow
	   address space pointer conversions.

       -mcache-size=cache-size
	   This option controls the version of libgcc that the compiler links
	   to an executable and selects a software-managed cache for accessing
	   variables in the "__ea" address space with a particular cache size.
	   Possible options for cache-size are 8, 16, 32, 64 and 128.  The
	   default cache size is 64KB.

       -matomic-updates
       -mno-atomic-updates
	   This option controls the version of libgcc that the compiler links
	   to an executable and selects whether atomic updates to the
	   software-managed cache of PPU-side variables are used.  If you use
	   atomic updates, changes to a PPU variable from SPU code using the
	   "__ea" named address space qualifier do not interfere with changes
	   to other PPU variables residing in the same cache line from PPU
	   code.  If you do not use atomic updates, such interference may
	   occur; however, writing back cache lines is more efficient.	The
	   default behavior is to use atomic updates.

       -mdual-nops
       -mdual-nops=n
	   By default, GCC inserts nops to increase dual issue when it expects
	   it to increase performance.	n can be a value from 0 to 10.	A
	   smaller n inserts fewer nops.  10 is the default, 0 is the same as
	   -mno-dual-nops.  Disabled with -Os.

       -mhint-max-nops=n
	   Maximum number of nops to insert for a branch hint.	A branch hint
	   must be at least 8 instructions away from the branch it is
	   affecting.  GCC inserts up to n nops to enforce this, otherwise it
	   does not generate the branch hint.

       -mhint-max-distance=n
	   The encoding of the branch hint instruction limits the hint to be
	   within 256 instructions of the branch it is affecting.  By default,
	   GCC makes sure it is within 125.

       -msafe-hints
	   Work around a hardware bug that causes the SPU to stall
	   indefinitely.  By default, GCC inserts the "hbrp" instruction to
	   make sure this stall won't happen.

   Options for System V
       These additional options are available on System V Release 4 for
       compatibility with other compilers on those systems:

       -G  Create a shared object.  It is recommended that -symbolic or
	   -shared be used instead.

       -Qy Identify the versions of each tool used by the compiler, in a
	   ".ident" assembler directive in the output.

       -Qn Refrain from adding ".ident" directives to the output file (this is
	   the default).

       -YP,dirs
	   Search the directories dirs, and no others, for libraries specified
	   with -l.

       -Ym,dir
	   Look in the directory dir to find the M4 preprocessor.  The
	   assembler uses this option.

   TILE-Gx Options
       These -m options are supported on the TILE-Gx:

       -mcmodel=small
	   Generate code for the small model.  The distance for direct calls
	   is limited to 500M in either direction.  PC-relative addresses are
	   32 bits.  Absolute addresses support the full address range.

       -mcmodel=large
	   Generate code for the large model.  There is no limitation on call
	   distance, pc-relative addresses, or absolute addresses.

       -mcpu=name
	   Selects the type of CPU to be targeted.  Currently the only
	   supported type is tilegx.

       -m32
       -m64
	   Generate code for a 32-bit or 64-bit environment.  The 32-bit
	   environment sets int, long, and pointer to 32 bits.	The 64-bit
	   environment sets int to 32 bits and long and pointer to 64 bits.

   TILEPro Options
       These -m options are supported on the TILEPro:

       -mcpu=name
	   Selects the type of CPU to be targeted.  Currently the only
	   supported type is tilepro.

       -m32
	   Generate code for a 32-bit environment, which sets int, long, and
	   pointer to 32 bits.	This is the only supported behavior so the
	   flag is essentially ignored.

   V850 Options
       These -m options are defined for V850 implementations:

       -mlong-calls
       -mno-long-calls
	   Treat all calls as being far away (near).  If calls are assumed to
	   be far away, the compiler always loads the function's address into
	   a register, and calls indirect through the pointer.

       -mno-ep
       -mep
	   Do not optimize (do optimize) basic blocks that use the same index
	   pointer 4 or more times to copy pointer into the "ep" register, and
	   use the shorter "sld" and "sst" instructions.  The -mep option is
	   on by default if you optimize.

       -mno-prolog-function
       -mprolog-function
	   Do not use (do use) external functions to save and restore
	   registers at the prologue and epilogue of a function.  The external
	   functions are slower, but use less code space if more than one
	   function saves the same number of registers.	 The -mprolog-function
	   option is on by default if you optimize.

       -mspace
	   Try to make the code as small as possible.  At present, this just
	   turns on the -mep and -mprolog-function options.

       -mtda=n
	   Put static or global variables whose size is n bytes or less into
	   the tiny data area that register "ep" points to.  The tiny data
	   area can hold up to 256 bytes in total (128 bytes for byte
	   references).

       -msda=n
	   Put static or global variables whose size is n bytes or less into
	   the small data area that register "gp" points to.  The small data
	   area can hold up to 64 kilobytes.

       -mzda=n
	   Put static or global variables whose size is n bytes or less into
	   the first 32 kilobytes of memory.

       -mv850
	   Specify that the target processor is the V850.

       -mv850e3v5
	   Specify that the target processor is the V850E3V5.  The
	   preprocessor constant __v850e3v5__ is defined if this option is
	   used.

       -mv850e2v4
	   Specify that the target processor is the V850E3V5.  This is an
	   alias for the -mv850e3v5 option.

       -mv850e2v3
	   Specify that the target processor is the V850E2V3.  The
	   preprocessor constant __v850e2v3__ is defined if this option is
	   used.

       -mv850e2
	   Specify that the target processor is the V850E2.  The preprocessor
	   constant __v850e2__ is defined if this option is used.

       -mv850e1
	   Specify that the target processor is the V850E1.  The preprocessor
	   constants __v850e1__ and __v850e__ are defined if this option is
	   used.

       -mv850es
	   Specify that the target processor is the V850ES.  This is an alias
	   for the -mv850e1 option.

       -mv850e
	   Specify that the target processor is the V850E.  The preprocessor
	   constant __v850e__ is defined if this option is used.

	   If neither -mv850 nor -mv850e nor -mv850e1 nor -mv850e2 nor
	   -mv850e2v3 nor -mv850e3v5 are defined then a default target
	   processor is chosen and the relevant __v850*__ preprocessor
	   constant is defined.

	   The preprocessor constants __v850 and __v851__ are always defined,
	   regardless of which processor variant is the target.

       -mdisable-callt
       -mno-disable-callt
	   This option suppresses generation of the "CALLT" instruction for
	   the v850e, v850e1, v850e2, v850e2v3 and v850e3v5 flavors of the
	   v850 architecture.

	   This option is enabled by default when the RH850 ABI is in use (see
	   -mrh850-abi), and disabled by default when the GCC ABI is in use.
	   If "CALLT" instructions are being generated then the C preprocessor
	   symbol "__V850_CALLT__" will be defined.

       -mrelax
       -mno-relax
	   Pass on (or do not pass on) the -mrelax command line option to the
	   assembler.

       -mlong-jumps
       -mno-long-jumps
	   Disable (or re-enable) the generation of PC-relative jump
	   instructions.

       -msoft-float
       -mhard-float
	   Disable (or re-enable) the generation of hardware floating point
	   instructions.  This option is only significant when the target
	   architecture is V850E2V3 or higher.	If hardware floating point
	   instructions are being generated then the C preprocessor symbol
	   "__FPU_OK__" will be defined, otherwise the symbol "__NO_FPU__"
	   will be defined.

       -mloop
	   Enables the use of the e3v5 LOOP instruction.  The use of this
	   instruction is not enabled by default when the e3v5 architecture is
	   selected because its use is still experimental.

       -mrh850-abi
       -mghs
	   Enables support for the RH850 version of the V850 ABI.  This is the
	   default.  With this version of the ABI the following rules apply:

	   o   Integer sized structures and unions are returned via a memory
	       pointer rather than a register.

	   o   Large structures and unions (more than 8 bytes in size) are
	       passed by value.

	   o   Functions are aligned to 16-bit boundaries.

	   o   The -m8byte-align command line option is supported.

	   o   The -mdisable-callt command line option is enabled by default.
	       The -mno-disable-callt command line option is not supported.

	   When this version of the ABI is enabled the C preprocessor symbol
	   "__V850_RH850_ABI__" is defined.

       -mgcc-abi
	   Enables support for the old GCC version of the V850 ABI.  With this
	   version of the ABI the following rules apply:

	   o   Integer sized structures and unions are returned in register
	       "r10".

	   o   Large structures and unions (more than 8 bytes in size) are
	       passed by reference.

	   o   Functions are aligned to 32-bit boundaries, unless optimizing
	       for size.

	   o   The -m8byte-align command line option is not supported.

	   o   The -mdisable-callt command line option is supported but not
	       enabled by default.

	   When this version of the ABI is enabled the C preprocessor symbol
	   "__V850_GCC_ABI__" is defined.

       -m8byte-align
       -mno-8byte-align
	   Enables support for "doubles" and "long long" types to be aligned
	   on 8-byte boundaries.  The default is to restrict the alignment of
	   all objects to at most 4-bytes.  When -m8byte-align is in effect
	   the C preprocessor symbol "__V850_8BYTE_ALIGN__" will be defined.

       -mbig-switch
	   Generate code suitable for big switch tables.  Use this option only
	   if the assembler/linker complain about out of range branches within
	   a switch table.

       -mapp-regs
	   This option causes r2 and r5 to be used in the code generated by
	   the compiler.  This setting is the default.

       -mno-app-regs
	   This option causes r2 and r5 to be treated as fixed registers.

   VAX Options
       These -m options are defined for the VAX:

       -munix
	   Do not output certain jump instructions ("aobleq" and so on) that
	   the Unix assembler for the VAX cannot handle across long ranges.

       -mgnu
	   Do output those jump instructions, on the assumption that the GNU
	   assembler is being used.

       -mg Output code for G-format floating-point numbers instead of
	   D-format.

   VMS Options
       These -m options are defined for the VMS implementations:

       -mvms-return-codes
	   Return VMS condition codes from "main". The default is to return
	   POSIX-style condition (e.g. error) codes.

       -mdebug-main=prefix
	   Flag the first routine whose name starts with prefix as the main
	   routine for the debugger.

       -mmalloc64
	   Default to 64-bit memory allocation routines.

       -mpointer-size=size
	   Set the default size of pointers. Possible options for size are 32
	   or short for 32 bit pointers, 64 or long for 64 bit pointers, and
	   no for supporting only 32 bit pointers.  The later option disables
	   "pragma pointer_size".

   VxWorks Options
       The options in this section are defined for all VxWorks targets.
       Options specific to the target hardware are listed with the other
       options for that target.

       -mrtp
	   GCC can generate code for both VxWorks kernels and real time
	   processes (RTPs).  This option switches from the former to the
	   latter.  It also defines the preprocessor macro "__RTP__".

       -non-static
	   Link an RTP executable against shared libraries rather than static
	   libraries.  The options -static and -shared can also be used for
	   RTPs; -static is the default.

       -Bstatic
       -Bdynamic
	   These options are passed down to the linker.	 They are defined for
	   compatibility with Diab.

       -Xbind-lazy
	   Enable lazy binding of function calls.  This option is equivalent
	   to -Wl,-z,now and is defined for compatibility with Diab.

       -Xbind-now
	   Disable lazy binding of function calls.  This option is the default
	   and is defined for compatibility with Diab.

   x86-64 Options
       These are listed under

   Xstormy16 Options
       These options are defined for Xstormy16:

       -msim
	   Choose startup files and linker script suitable for the simulator.

   Xtensa Options
       These options are supported for Xtensa targets:

       -mconst16
       -mno-const16
	   Enable or disable use of "CONST16" instructions for loading
	   constant values.  The "CONST16" instruction is currently not a
	   standard option from Tensilica.  When enabled, "CONST16"
	   instructions are always used in place of the standard "L32R"
	   instructions.  The use of "CONST16" is enabled by default only if
	   the "L32R" instruction is not available.

       -mfused-madd
       -mno-fused-madd
	   Enable or disable use of fused multiply/add and multiply/subtract
	   instructions in the floating-point option.  This has no effect if
	   the floating-point option is not also enabled.  Disabling fused
	   multiply/add and multiply/subtract instructions forces the compiler
	   to use separate instructions for the multiply and add/subtract
	   operations.	This may be desirable in some cases where strict IEEE
	   754-compliant results are required: the fused multiply add/subtract
	   instructions do not round the intermediate result, thereby
	   producing results with more bits of precision than specified by the
	   IEEE standard.  Disabling fused multiply add/subtract instructions
	   also ensures that the program output is not sensitive to the
	   compiler's ability to combine multiply and add/subtract operations.

       -mserialize-volatile
       -mno-serialize-volatile
	   When this option is enabled, GCC inserts "MEMW" instructions before
	   "volatile" memory references to guarantee sequential consistency.
	   The default is -mserialize-volatile.	 Use -mno-serialize-volatile
	   to omit the "MEMW" instructions.

       -mforce-no-pic
	   For targets, like GNU/Linux, where all user-mode Xtensa code must
	   be position-independent code (PIC), this option disables PIC for
	   compiling kernel code.

       -mtext-section-literals
       -mno-text-section-literals
	   Control the treatment of literal pools.  The default is
	   -mno-text-section-literals, which places literals in a separate
	   section in the output file.	This allows the literal pool to be
	   placed in a data RAM/ROM, and it also allows the linker to combine
	   literal pools from separate object files to remove redundant
	   literals and improve code size.  With -mtext-section-literals, the
	   literals are interspersed in the text section in order to keep them
	   as close as possible to their references.  This may be necessary
	   for large assembly files.

       -mtarget-align
       -mno-target-align
	   When this option is enabled, GCC instructs the assembler to
	   automatically align instructions to reduce branch penalties at the
	   expense of some code density.  The assembler attempts to widen
	   density instructions to align branch targets and the instructions
	   following call instructions.	 If there are not enough preceding
	   safe density instructions to align a target, no widening is
	   performed.  The default is -mtarget-align.  These options do not
	   affect the treatment of auto-aligned instructions like "LOOP",
	   which the assembler always aligns, either by widening density
	   instructions or by inserting NOP instructions.

       -mlongcalls
       -mno-longcalls
	   When this option is enabled, GCC instructs the assembler to
	   translate direct calls to indirect calls unless it can determine
	   that the target of a direct call is in the range allowed by the
	   call instruction.  This translation typically occurs for calls to
	   functions in other source files.  Specifically, the assembler
	   translates a direct "CALL" instruction into an "L32R" followed by a
	   "CALLX" instruction.	 The default is -mno-longcalls.	 This option
	   should be used in programs where the call target can potentially be
	   out of range.  This option is implemented in the assembler, not the
	   compiler, so the assembly code generated by GCC still shows direct
	   call instructions---look at the disassembled object code to see the
	   actual instructions.	 Note that the assembler uses an indirect call
	   for every cross-file call, not just those that really are out of
	   range.

   zSeries Options
       These are listed under

   Options for Code Generation Conventions
       These machine-independent options control the interface conventions
       used in code generation.

       Most of them have both positive and negative forms; the negative form
       of -ffoo is -fno-foo.  In the table below, only one of the forms is
       listed---the one that is not the default.  You can figure out the other
       form by either removing no- or adding it.

       -fbounds-check
	   For front ends that support it, generate additional code to check
	   that indices used to access arrays are within the declared range.
	   This is currently only supported by the Java and Fortran front
	   ends, where this option defaults to true and false respectively.

       -fstack-reuse=reuse-level
	   This option controls stack space reuse for user declared local/auto
	   variables and compiler generated temporaries.  reuse_level can be
	   all, named_vars, or none. all enables stack reuse for all local
	   variables and temporaries, named_vars enables the reuse only for
	   user defined local variables with names, and none disables stack
	   reuse completely. The default value is all. The option is needed
	   when the program extends the lifetime of a scoped local variable or
	   a compiler generated temporary beyond the end point defined by the
	   language.  When a lifetime of a variable ends, and if the variable
	   lives in memory, the optimizing compiler has the freedom to reuse
	   its stack space with other temporaries or scoped local variables
	   whose live range does not overlap with it. Legacy code extending
	   local lifetime will likely to break with the stack reuse
	   optimization.

	   For example,

		      int *p;
		      {
			int local1;

			p = &local1;
			local1 = 10;
			....
		      }
		      {
			 int local2;
			 local2 = 20;
			 ...
		      }

		      if (*p == 10)  // out of scope use of local1
			{

			}

	   Another example:

		      struct A
		      {
			  A(int k) : i(k), j(k) { }
			  int i;
			  int j;
		      };

		      A *ap;

		      void foo(const A& ar)
		      {
			 ap = &ar;
		      }

		      void bar()
		      {
			 foo(A(10)); // temp object's lifetime ends when foo returns

			 {
			   A a(20);
			   ....
			 }
			 ap->i+= 10;  // ap references out of scope temp whose space
				      // is reused with a. What is the value of ap->i?
		      }

	   The lifetime of a compiler generated temporary is well defined by
	   the C++ standard. When a lifetime of a temporary ends, and if the
	   temporary lives in memory, the optimizing compiler has the freedom
	   to reuse its stack space with other temporaries or scoped local
	   variables whose live range does not overlap with it. However some
	   of the legacy code relies on the behavior of older compilers in
	   which temporaries' stack space is not reused, the aggressive stack
	   reuse can lead to runtime errors. This option is used to control
	   the temporary stack reuse optimization.

       -ftrapv
	   This option generates traps for signed overflow on addition,
	   subtraction, multiplication operations.

       -fwrapv
	   This option instructs the compiler to assume that signed arithmetic
	   overflow of addition, subtraction and multiplication wraps around
	   using twos-complement representation.  This flag enables some
	   optimizations and disables others.  This option is enabled by
	   default for the Java front end, as required by the Java language
	   specification.

       -fexceptions
	   Enable exception handling.  Generates extra code needed to
	   propagate exceptions.  For some targets, this implies GCC generates
	   frame unwind information for all functions, which can produce
	   significant data size overhead, although it does not affect
	   execution.  If you do not specify this option, GCC enables it by
	   default for languages like C++ that normally require exception
	   handling, and disables it for languages like C that do not normally
	   require it.	However, you may need to enable this option when
	   compiling C code that needs to interoperate properly with exception
	   handlers written in C++.  You may also wish to disable this option
	   if you are compiling older C++ programs that don't use exception
	   handling.

       -fnon-call-exceptions
	   Generate code that allows trapping instructions to throw
	   exceptions.	Note that this requires platform-specific runtime
	   support that does not exist everywhere.  Moreover, it only allows
	   trapping instructions to throw exceptions, i.e. memory references
	   or floating-point instructions.  It does not allow exceptions to be
	   thrown from arbitrary signal handlers such as "SIGALRM".

       -fdelete-dead-exceptions
	   Consider that instructions that may throw exceptions but don't
	   otherwise contribute to the execution of the program can be
	   optimized away.  This option is enabled by default for the Ada
	   front end, as permitted by the Ada language specification.
	   Optimization passes that cause dead exceptions to be removed are
	   enabled independently at different optimization levels.

       -funwind-tables
	   Similar to -fexceptions, except that it just generates any needed
	   static data, but does not affect the generated code in any other
	   way.	 You normally do not need to enable this option; instead, a
	   language processor that needs this handling enables it on your
	   behalf.

       -fasynchronous-unwind-tables
	   Generate unwind table in DWARF 2 format, if supported by target
	   machine.  The table is exact at each instruction boundary, so it
	   can be used for stack unwinding from asynchronous events (such as
	   debugger or garbage collector).

       -fno-gnu-unique
	   On systems with recent GNU assembler and C library, the C++
	   compiler uses the "STB_GNU_UNIQUE" binding to make sure that
	   definitions of template static data members and static local
	   variables in inline functions are unique even in the presence of
	   "RTLD_LOCAL"; this is necessary to avoid problems with a library
	   used by two different "RTLD_LOCAL" plugins depending on a
	   definition in one of them and therefore disagreeing with the other
	   one about the binding of the symbol.	 But this causes "dlclose" to
	   be ignored for affected DSOs; if your program relies on
	   reinitialization of a DSO via "dlclose" and "dlopen", you can use
	   -fno-gnu-unique.

       -fpcc-struct-return
	   Return "short" "struct" and "union" values in memory like longer
	   ones, rather than in registers.  This convention is less efficient,
	   but it has the advantage of allowing intercallability between GCC-
	   compiled files and files compiled with other compilers,
	   particularly the Portable C Compiler (pcc).

	   The precise convention for returning structures in memory depends
	   on the target configuration macros.

	   Short structures and unions are those whose size and alignment
	   match that of some integer type.

	   Warning: code compiled with the -fpcc-struct-return switch is not
	   binary compatible with code compiled with the -freg-struct-return
	   switch.  Use it to conform to a non-default application binary
	   interface.

       -freg-struct-return
	   Return "struct" and "union" values in registers when possible.
	   This is more efficient for small structures than
	   -fpcc-struct-return.

	   If you specify neither -fpcc-struct-return nor -freg-struct-return,
	   GCC defaults to whichever convention is standard for the target.
	   If there is no standard convention, GCC defaults to
	   -fpcc-struct-return, except on targets where GCC is the principal
	   compiler.  In those cases, we can choose the standard, and we chose
	   the more efficient register return alternative.

	   Warning: code compiled with the -freg-struct-return switch is not
	   binary compatible with code compiled with the -fpcc-struct-return
	   switch.  Use it to conform to a non-default application binary
	   interface.

       -fshort-enums
	   Allocate to an "enum" type only as many bytes as it needs for the
	   declared range of possible values.  Specifically, the "enum" type
	   is equivalent to the smallest integer type that has enough room.

	   Warning: the -fshort-enums switch causes GCC to generate code that
	   is not binary compatible with code generated without that switch.
	   Use it to conform to a non-default application binary interface.

       -fshort-double
	   Use the same size for "double" as for "float".

	   Warning: the -fshort-double switch causes GCC to generate code that
	   is not binary compatible with code generated without that switch.
	   Use it to conform to a non-default application binary interface.

       -fshort-wchar
	   Override the underlying type for wchar_t to be short unsigned int
	   instead of the default for the target.  This option is useful for
	   building programs to run under WINE.

	   Warning: the -fshort-wchar switch causes GCC to generate code that
	   is not binary compatible with code generated without that switch.
	   Use it to conform to a non-default application binary interface.

       -fno-common
	   In C code, controls the placement of uninitialized global
	   variables.  Unix C compilers have traditionally permitted multiple
	   definitions of such variables in different compilation units by
	   placing the variables in a common block.  This is the behavior
	   specified by -fcommon, and is the default for GCC on most targets.
	   On the other hand, this behavior is not required by ISO C, and on
	   some targets may carry a speed or code size penalty on variable
	   references.	The -fno-common option specifies that the compiler
	   should place uninitialized global variables in the data section of
	   the object file, rather than generating them as common blocks.
	   This has the effect that if the same variable is declared (without
	   "extern") in two different compilations, you get a multiple-
	   definition error when you link them.	 In this case, you must
	   compile with -fcommon instead.  Compiling with -fno-common is
	   useful on targets for which it provides better performance, or if
	   you wish to verify that the program will work on other systems that
	   always treat uninitialized variable declarations this way.

       -fno-ident
	   Ignore the #ident directive.

       -finhibit-size-directive
	   Don't output a ".size" assembler directive, or anything else that
	   would cause trouble if the function is split in the middle, and the
	   two halves are placed at locations far apart in memory.  This
	   option is used when compiling crtstuff.c; you should not need to
	   use it for anything else.

       -fverbose-asm
	   Put extra commentary information in the generated assembly code to
	   make it more readable.  This option is generally only of use to
	   those who actually need to read the generated assembly code
	   (perhaps while debugging the compiler itself).

	   -fno-verbose-asm, the default, causes the extra information to be
	   omitted and is useful when comparing two assembler files.

       -frecord-gcc-switches
	   This switch causes the command line used to invoke the compiler to
	   be recorded into the object file that is being created.  This
	   switch is only implemented on some targets and the exact format of
	   the recording is target and binary file format dependent, but it
	   usually takes the form of a section containing ASCII text.  This
	   switch is related to the -fverbose-asm switch, but that switch only
	   records information in the assembler output file as comments, so it
	   never reaches the object file.  See also -grecord-gcc-switches for
	   another way of storing compiler options into the object file.

       -fpic
	   Generate position-independent code (PIC) suitable for use in a
	   shared library, if supported for the target machine.	 Such code
	   accesses all constant addresses through a global offset table
	   (GOT).  The dynamic loader resolves the GOT entries when the
	   program starts (the dynamic loader is not part of GCC; it is part
	   of the operating system).  If the GOT size for the linked
	   executable exceeds a machine-specific maximum size, you get an
	   error message from the linker indicating that -fpic does not work;
	   in that case, recompile with -fPIC instead.	(These maximums are 8k
	   on the SPARC and 32k on the m68k and RS/6000.  The 386 has no such
	   limit.)

	   Position-independent code requires special support, and therefore
	   works only on certain machines.  For the 386, GCC supports PIC for
	   System V but not for the Sun 386i.  Code generated for the IBM
	   RS/6000 is always position-independent.

	   When this flag is set, the macros "__pic__" and "__PIC__" are
	   defined to 1.

       -fPIC
	   If supported for the target machine, emit position-independent
	   code, suitable for dynamic linking and avoiding any limit on the
	   size of the global offset table.  This option makes a difference on
	   the m68k, PowerPC and SPARC.

	   Position-independent code requires special support, and therefore
	   works only on certain machines.

	   When this flag is set, the macros "__pic__" and "__PIC__" are
	   defined to 2.

       -fpie
       -fPIE
	   These options are similar to -fpic and -fPIC, but generated
	   position independent code can be only linked into executables.
	   Usually these options are used when -pie GCC option is used during
	   linking.

	   -fpie and -fPIE both define the macros "__pie__" and "__PIE__".
	   The macros have the value 1 for -fpie and 2 for -fPIE.

       -fno-jump-tables
	   Do not use jump tables for switch statements even where it would be
	   more efficient than other code generation strategies.  This option
	   is of use in conjunction with -fpic or -fPIC for building code that
	   forms part of a dynamic linker and cannot reference the address of
	   a jump table.  On some targets, jump tables do not require a GOT
	   and this option is not needed.

       -ffixed-reg
	   Treat the register named reg as a fixed register; generated code
	   should never refer to it (except perhaps as a stack pointer, frame
	   pointer or in some other fixed role).

	   reg must be the name of a register.	The register names accepted
	   are machine-specific and are defined in the "REGISTER_NAMES" macro
	   in the machine description macro file.

	   This flag does not have a negative form, because it specifies a
	   three-way choice.

       -fcall-used-reg
	   Treat the register named reg as an allocable register that is
	   clobbered by function calls.	 It may be allocated for temporaries
	   or variables that do not live across a call.	 Functions compiled
	   this way do not save and restore the register reg.

	   It is an error to use this flag with the frame pointer or stack
	   pointer.  Use of this flag for other registers that have fixed
	   pervasive roles in the machine's execution model produces
	   disastrous results.

	   This flag does not have a negative form, because it specifies a
	   three-way choice.

       -fcall-saved-reg
	   Treat the register named reg as an allocable register saved by
	   functions.  It may be allocated even for temporaries or variables
	   that live across a call.  Functions compiled this way save and
	   restore the register reg if they use it.

	   It is an error to use this flag with the frame pointer or stack
	   pointer.  Use of this flag for other registers that have fixed
	   pervasive roles in the machine's execution model produces
	   disastrous results.

	   A different sort of disaster results from the use of this flag for
	   a register in which function values may be returned.

	   This flag does not have a negative form, because it specifies a
	   three-way choice.

       -fpack-struct[=n]
	   Without a value specified, pack all structure members together
	   without holes.  When a value is specified (which must be a small
	   power of two), pack structure members according to this value,
	   representing the maximum alignment (that is, objects with default
	   alignment requirements larger than this are output potentially
	   unaligned at the next fitting location.

	   Warning: the -fpack-struct switch causes GCC to generate code that
	   is not binary compatible with code generated without that switch.
	   Additionally, it makes the code suboptimal.	Use it to conform to a
	   non-default application binary interface.

       -finstrument-functions
	   Generate instrumentation calls for entry and exit to functions.
	   Just after function entry and just before function exit, the
	   following profiling functions are called with the address of the
	   current function and its call site.	(On some platforms,
	   "__builtin_return_address" does not work beyond the current
	   function, so the call site information may not be available to the
	   profiling functions otherwise.)

		   void __cyg_profile_func_enter (void *this_fn,
						  void *call_site);
		   void __cyg_profile_func_exit	 (void *this_fn,
						  void *call_site);

	   The first argument is the address of the start of the current
	   function, which may be looked up exactly in the symbol table.

	   This instrumentation is also done for functions expanded inline in
	   other functions.  The profiling calls indicate where, conceptually,
	   the inline function is entered and exited.  This means that
	   addressable versions of such functions must be available.  If all
	   your uses of a function are expanded inline, this may mean an
	   additional expansion of code size.  If you use extern inline in
	   your C code, an addressable version of such functions must be
	   provided.  (This is normally the case anyway, but if you get lucky
	   and the optimizer always expands the functions inline, you might
	   have gotten away without providing static copies.)

	   A function may be given the attribute "no_instrument_function", in
	   which case this instrumentation is not done.	 This can be used, for
	   example, for the profiling functions listed above, high-priority
	   interrupt routines, and any functions from which the profiling
	   functions cannot safely be called (perhaps signal handlers, if the
	   profiling routines generate output or allocate memory).

       -finstrument-functions-exclude-file-list=file,file,...
	   Set the list of functions that are excluded from instrumentation
	   (see the description of "-finstrument-functions").  If the file
	   that contains a function definition matches with one of file, then
	   that function is not instrumented.  The match is done on
	   substrings: if the file parameter is a substring of the file name,
	   it is considered to be a match.

	   For example:

		   -finstrument-functions-exclude-file-list=/bits/stl,include/sys

	   excludes any inline function defined in files whose pathnames
	   contain "/bits/stl" or "include/sys".

	   If, for some reason, you want to include letter ',' in one of sym,
	   write ','. For example,
	   "-finstrument-functions-exclude-file-list=',,tmp'" (note the single
	   quote surrounding the option).

       -finstrument-functions-exclude-function-list=sym,sym,...
	   This is similar to "-finstrument-functions-exclude-file-list", but
	   this option sets the list of function names to be excluded from
	   instrumentation.  The function name to be matched is its user-
	   visible name, such as "vector<int> blah(const vector<int> &)", not
	   the internal mangled name (e.g., "_Z4blahRSt6vectorIiSaIiEE").  The
	   match is done on substrings: if the sym parameter is a substring of
	   the function name, it is considered to be a match.  For C99 and C++
	   extended identifiers, the function name must be given in UTF-8, not
	   using universal character names.

       -fstack-check
	   Generate code to verify that you do not go beyond the boundary of
	   the stack.  You should specify this flag if you are running in an
	   environment with multiple threads, but you only rarely need to
	   specify it in a single-threaded environment since stack overflow is
	   automatically detected on nearly all systems if there is only one
	   stack.

	   Note that this switch does not actually cause checking to be done;
	   the operating system or the language runtime must do that.  The
	   switch causes generation of code to ensure that they see the stack
	   being extended.

	   You can additionally specify a string parameter: "no" means no
	   checking, "generic" means force the use of old-style checking,
	   "specific" means use the best checking method and is equivalent to
	   bare -fstack-check.

	   Old-style checking is a generic mechanism that requires no specific
	   target support in the compiler but comes with the following
	   drawbacks:

	   1.  Modified allocation strategy for large objects: they are always
	       allocated dynamically if their size exceeds a fixed threshold.

	   2.  Fixed limit on the size of the static frame of functions: when
	       it is topped by a particular function, stack checking is not
	       reliable and a warning is issued by the compiler.

	   3.  Inefficiency: because of both the modified allocation strategy
	       and the generic implementation, code performance is hampered.

	   Note that old-style stack checking is also the fallback method for
	   "specific" if no target support has been added in the compiler.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
	   Generate code to ensure that the stack does not grow beyond a
	   certain value, either the value of a register or the address of a
	   symbol.  If a larger stack is required, a signal is raised at run
	   time.  For most targets, the signal is raised before the stack
	   overruns the boundary, so it is possible to catch the signal
	   without taking special precautions.

	   For instance, if the stack starts at absolute address 0x80000000
	   and grows downwards, you can use the flags
	   -fstack-limit-symbol=__stack_limit and
	   -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of
	   128KB.  Note that this may only work with the GNU linker.

       -fsplit-stack
	   Generate code to automatically split the stack before it overflows.
	   The resulting program has a discontiguous stack which can only
	   overflow if the program is unable to allocate any more memory.
	   This is most useful when running threaded programs, as it is no
	   longer necessary to calculate a good stack size to use for each
	   thread.  This is currently only implemented for the i386 and x86_64
	   back ends running GNU/Linux.

	   When code compiled with -fsplit-stack calls code compiled without
	   -fsplit-stack, there may not be much stack space available for the
	   latter code to run.	If compiling all code, including library code,
	   with -fsplit-stack is not an option, then the linker can fix up
	   these calls so that the code compiled without -fsplit-stack always
	   has a large stack.  Support for this is implemented in the gold
	   linker in GNU binutils release 2.21 and later.

       -fleading-underscore
	   This option and its counterpart, -fno-leading-underscore, forcibly
	   change the way C symbols are represented in the object file.	 One
	   use is to help link with legacy assembly code.

	   Warning: the -fleading-underscore switch causes GCC to generate
	   code that is not binary compatible with code generated without that
	   switch.  Use it to conform to a non-default application binary
	   interface.  Not all targets provide complete support for this
	   switch.

       -ftls-model=model
	   Alter the thread-local storage model to be used.  The model
	   argument should be one of "global-dynamic", "local-dynamic",
	   "initial-exec" or "local-exec".

	   The default without -fpic is "initial-exec"; with -fpic the default
	   is "global-dynamic".

       -fvisibility=default|internal|hidden|protected
	   Set the default ELF image symbol visibility to the specified
	   option---all symbols are marked with this unless overridden within
	   the code.  Using this feature can very substantially improve
	   linking and load times of shared object libraries, produce more
	   optimized code, provide near-perfect API export and prevent symbol
	   clashes.  It is strongly recommended that you use this in any
	   shared objects you distribute.

	   Despite the nomenclature, "default" always means public; i.e.,
	   available to be linked against from outside the shared object.
	   "protected" and "internal" are pretty useless in real-world usage
	   so the only other commonly used option is "hidden".	The default if
	   -fvisibility isn't specified is "default", i.e., make every symbol
	   public---this causes the same behavior as previous versions of GCC.

	   A good explanation of the benefits offered by ensuring ELF symbols
	   have the correct visibility is given by "How To Write Shared
	   Libraries" by Ulrich Drepper (which can be found at
	   <http://people.redhat.com/~drepper/>)---however a superior solution
	   made possible by this option to marking things hidden when the
	   default is public is to make the default hidden and mark things
	   public.  This is the norm with DLLs on Windows and with
	   -fvisibility=hidden and "__attribute__ ((visibility("default")))"
	   instead of "__declspec(dllexport)" you get almost identical
	   semantics with identical syntax.  This is a great boon to those
	   working with cross-platform projects.

	   For those adding visibility support to existing code, you may find
	   #pragma GCC visibility of use.  This works by you enclosing the
	   declarations you wish to set visibility for with (for example)
	   #pragma GCC visibility push(hidden) and #pragma GCC visibility pop.
	   Bear in mind that symbol visibility should be viewed as part of the
	   API interface contract and thus all new code should always specify
	   visibility when it is not the default; i.e., declarations only for
	   use within the local DSO should always be marked explicitly as
	   hidden as so to avoid PLT indirection overheads---making this
	   abundantly clear also aids readability and self-documentation of
	   the code.  Note that due to ISO C++ specification requirements,
	   "operator new" and "operator delete" must always be of default
	   visibility.

	   Be aware that headers from outside your project, in particular
	   system headers and headers from any other library you use, may not
	   be expecting to be compiled with visibility other than the default.
	   You may need to explicitly say #pragma GCC visibility push(default)
	   before including any such headers.

	   extern declarations are not affected by -fvisibility, so a lot of
	   code can be recompiled with -fvisibility=hidden with no
	   modifications.  However, this means that calls to "extern"
	   functions with no explicit visibility use the PLT, so it is more
	   effective to use "__attribute ((visibility))" and/or "#pragma GCC
	   visibility" to tell the compiler which "extern" declarations should
	   be treated as hidden.

	   Note that -fvisibility does affect C++ vague linkage entities. This
	   means that, for instance, an exception class that is be thrown
	   between DSOs must be explicitly marked with default visibility so
	   that the type_info nodes are unified between the DSOs.

	   An overview of these techniques, their benefits and how to use them
	   is at <http://gcc.gnu.org/wiki/Visibility>.

       -fstrict-volatile-bitfields
	   This option should be used if accesses to volatile bit-fields (or
	   other structure fields, although the compiler usually honors those
	   types anyway) should use a single access of the width of the
	   field's type, aligned to a natural alignment if possible.  For
	   example, targets with memory-mapped peripheral registers might
	   require all such accesses to be 16 bits wide; with this flag you
	   can declare all peripheral bit-fields as "unsigned short" (assuming
	   short is 16 bits on these targets) to force GCC to use 16-bit
	   accesses instead of, perhaps, a more efficient 32-bit access.

	   If this option is disabled, the compiler uses the most efficient
	   instruction.	 In the previous example, that might be a 32-bit load
	   instruction, even though that accesses bytes that do not contain
	   any portion of the bit-field, or memory-mapped registers unrelated
	   to the one being updated.

	   If the target requires strict alignment, and honoring the field
	   type would require violating this alignment, a warning is issued.
	   If the field has "packed" attribute, the access is done without
	   honoring the field type.  If the field doesn't have "packed"
	   attribute, the access is done honoring the field type.  In both
	   cases, GCC assumes that the user knows something about the target
	   hardware that it is unaware of.

	   The default value of this option is determined by the application
	   binary interface for the target processor.

       -fsync-libcalls
	   This option controls whether any out-of-line instance of the
	   "__sync" family of functions may be used to implement the C++11
	   "__atomic" family of functions.

	   The default value of this option is enabled, thus the only useful
	   form of the option is -fno-sync-libcalls.  This option is used in
	   the implementation of the libatomic runtime library.

ENVIRONMENT
       This section describes several environment variables that affect how
       GCC operates.  Some of them work by specifying directories or prefixes
       to use when searching for various kinds of files.  Some are used to
       specify other aspects of the compilation environment.

       Note that you can also specify places to search using options such as
       -B, -I and -L.  These take precedence over places specified using
       environment variables, which in turn take precedence over those
       specified by the configuration of GCC.

       LANG
       LC_CTYPE
       LC_MESSAGES
       LC_ALL
	   These environment variables control the way that GCC uses
	   localization information which allows GCC to work with different
	   national conventions.  GCC inspects the locale categories LC_CTYPE
	   and LC_MESSAGES if it has been configured to do so.	These locale
	   categories can be set to any value supported by your installation.
	   A typical value is en_GB.UTF-8 for English in the United Kingdom
	   encoded in UTF-8.

	   The LC_CTYPE environment variable specifies character
	   classification.  GCC uses it to determine the character boundaries
	   in a string; this is needed for some multibyte encodings that
	   contain quote and escape characters that are otherwise interpreted
	   as a string end or escape.

	   The LC_MESSAGES environment variable specifies the language to use
	   in diagnostic messages.

	   If the LC_ALL environment variable is set, it overrides the value
	   of LC_CTYPE and LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES
	   default to the value of the LANG environment variable.  If none of
	   these variables are set, GCC defaults to traditional C English
	   behavior.

       TMPDIR
	   If TMPDIR is set, it specifies the directory to use for temporary
	   files.  GCC uses temporary files to hold the output of one stage of
	   compilation which is to be used as input to the next stage: for
	   example, the output of the preprocessor, which is the input to the
	   compiler proper.

       GCC_COMPARE_DEBUG
	   Setting GCC_COMPARE_DEBUG is nearly equivalent to passing
	   -fcompare-debug to the compiler driver.  See the documentation of
	   this option for more details.

       GCC_EXEC_PREFIX
	   If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the
	   names of the subprograms executed by the compiler.  No slash is
	   added when this prefix is combined with the name of a subprogram,
	   but you can specify a prefix that ends with a slash if you wish.

	   If GCC_EXEC_PREFIX is not set, GCC attempts to figure out an
	   appropriate prefix to use based on the pathname it is invoked with.

	   If GCC cannot find the subprogram using the specified prefix, it
	   tries looking in the usual places for the subprogram.

	   The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/ where
	   prefix is the prefix to the installed compiler. In many cases
	   prefix is the value of "prefix" when you ran the configure script.

	   Other prefixes specified with -B take precedence over this prefix.

	   This prefix is also used for finding files such as crt0.o that are
	   used for linking.

	   In addition, the prefix is used in an unusual way in finding the
	   directories to search for header files.  For each of the standard
	   directories whose name normally begins with /usr/local/lib/gcc
	   (more precisely, with the value of GCC_INCLUDE_DIR), GCC tries
	   replacing that beginning with the specified prefix to produce an
	   alternate directory name.  Thus, with -Bfoo/, GCC searches foo/bar
	   just before it searches the standard directory /usr/local/lib/bar.
	   If a standard directory begins with the configured prefix then the
	   value of prefix is replaced by GCC_EXEC_PREFIX when looking for
	   header files.

       COMPILER_PATH
	   The value of COMPILER_PATH is a colon-separated list of
	   directories, much like PATH.	 GCC tries the directories thus
	   specified when searching for subprograms, if it can't find the
	   subprograms using GCC_EXEC_PREFIX.

       LIBRARY_PATH
	   The value of LIBRARY_PATH is a colon-separated list of directories,
	   much like PATH.  When configured as a native compiler, GCC tries
	   the directories thus specified when searching for special linker
	   files, if it can't find them using GCC_EXEC_PREFIX.	Linking using
	   GCC also uses these directories when searching for ordinary
	   libraries for the -l option (but directories specified with -L come
	   first).

       LANG
	   This variable is used to pass locale information to the compiler.
	   One way in which this information is used is to determine the
	   character set to be used when character literals, string literals
	   and comments are parsed in C and C++.  When the compiler is
	   configured to allow multibyte characters, the following values for
	   LANG are recognized:

	   C-JIS
	       Recognize JIS characters.

	   C-SJIS
	       Recognize SJIS characters.

	   C-EUCJP
	       Recognize EUCJP characters.

	   If LANG is not defined, or if it has some other value, then the
	   compiler uses "mblen" and "mbtowc" as defined by the default locale
	   to recognize and translate multibyte characters.

       Some additional environment variables affect the behavior of the
       preprocessor.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
	   Each variable's value is a list of directories separated by a
	   special character, much like PATH, in which to look for header
	   files.  The special character, "PATH_SEPARATOR", is target-
	   dependent and determined at GCC build time.	For Microsoft Windows-
	   based targets it is a semicolon, and for almost all other targets
	   it is a colon.

	   CPATH specifies a list of directories to be searched as if
	   specified with -I, but after any paths given with -I options on the
	   command line.  This environment variable is used regardless of
	   which language is being preprocessed.

	   The remaining environment variables apply only when preprocessing
	   the particular language indicated.  Each specifies a list of
	   directories to be searched as if specified with -isystem, but after
	   any paths given with -isystem options on the command line.

	   In all these variables, an empty element instructs the compiler to
	   search its current working directory.  Empty elements can appear at
	   the beginning or end of a path.  For instance, if the value of
	   CPATH is ":/special/include", that has the same effect as
	   -I. -I/special/include.

       DEPENDENCIES_OUTPUT
	   If this variable is set, its value specifies how to output
	   dependencies for Make based on the non-system header files
	   processed by the compiler.  System header files are ignored in the
	   dependency output.

	   The value of DEPENDENCIES_OUTPUT can be just a file name, in which
	   case the Make rules are written to that file, guessing the target
	   name from the source file name.  Or the value can have the form
	   file target, in which case the rules are written to file file using
	   target as the target name.

	   In other words, this environment variable is equivalent to
	   combining the options -MM and -MF, with an optional -MT switch too.

       SUNPRO_DEPENDENCIES
	   This variable is the same as DEPENDENCIES_OUTPUT (see above),
	   except that system header files are not ignored, so it implies -M
	   rather than -MM.  However, the dependence on the main input file is
	   omitted.

BUGS
       For instructions on reporting bugs, see
       <http://bugzilla.redhat.com/bugzilla>.

FOOTNOTES
       1.  On some systems, gcc -shared needs to build supplementary stub code
	   for constructors to work.  On multi-libbed systems, gcc -shared
	   must select the correct support libraries to link against.  Failing
	   to supply the correct flags may lead to subtle defects.  Supplying
	   them in cases where they are not necessary is innocuous.

SEE ALSO
       gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1), gdb(1),
       adb(1), dbx(1), sdb(1) and the Info entries for gcc, cpp, as, ld,
       binutils and gdb.

AUTHOR
       See the Info entry for gcc, or
       <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for contributors
       to GCC.

COPYRIGHT
       Copyright (c) 1988-2013 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.3 or
       any later version published by the Free Software Foundation; with the
       Invariant Sections being "GNU General Public License" and "Funding Free
       Software", the Front-Cover texts being (a) (see below), and with the
       Back-Cover Texts being (b) (see below).	A copy of the license is
       included in the gfdl(7) man page.

       (a) The FSF's Front-Cover Text is:

	    A GNU Manual

       (b) The FSF's Back-Cover Text is:

	    You have freedom to copy and modify this GNU Manual, like GNU
	    software.  Copies published by the Free Software Foundation raise
	    funds for GNU development.



gcc-4.8.3			  2014-09-11				GCC(1)