@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
-@c 2000, 2001 Free Software Foundation, Inc.
+@c 2000, 2001, 2002 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
@ignore
@c man begin COPYRIGHT
Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997,
-1998, 1999, 2000, 2001 Free Software Foundation, Inc.
-
-Permission is granted to make and distribute verbatim copies of this
-manual provided the copyright notice and this permission notice are
-preserved on all copies.
-
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided also that the
-entire resulting derived work is distributed under the terms of a
-permission notice identical to this one.
-
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions,
-except that this permission notice may be included in translations
-approved by the Free Software Foundation instead of in the original
-English.
+1998, 1999, 2000, 2001, 2002 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 1.1 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.
@c man end
@c Set file name and title for the man page.
@setfilename gcc
remainder. @samp{g++} accepts mostly the same options as @samp{gcc}.
@c man end
@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7),
cpp(1), gcov(1), g77(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1)
and the Info entries for @file{gcc}, @file{cpp}, @file{g77}, @file{as},
@file{ld}, @file{binutils} and @file{gdb}.
script to report bugs is recommended.
@c man end
@c man begin AUTHOR
-See the Info entry for @file{gcc}, or
-@w{@uref{http://gcc.gnu.org/thanks.html}}, for contributors to GCC@.
+See the Info entry for @command{gcc}, or
+@w{@uref{http://gcc.gnu.org/onlinedocs/gcc/Contributors.html}},
+for contributors to GCC@.
@c man end
@end ignore
@xref{C Dialect Options,,Options Controlling C Dialect}.
@gccoptlist{
-ansi -std=@var{standard} -aux-info @var{filename} @gol
--fno-asm -fno-builtin @gol
+-fno-asm -fno-builtin -fno-builtin-@var{function} @gol
-fhosted -ffreestanding @gol
-trigraphs -traditional -traditional-cpp @gol
-fallow-single-precision -fcond-mismatch @gol
-fno-elide-constructors @gol
-fno-enforce-eh-specs -fexternal-templates @gol
-falt-external-templates @gol
--ffor-scope -fno-for-scope -fno-gnu-keywords -fno-honor-std @gol
+-ffor-scope -fno-for-scope -fno-gnu-keywords @gol
-fno-implicit-templates @gol
-fno-implicit-inline-templates @gol
-fno-implement-inlines -fms-extensions @gol
-fsyntax-only -pedantic -pedantic-errors @gol
-w -W -Wall -Waggregate-return @gol
-Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment @gol
--Wconversion -Wdisabled-optimization -Werror @gol
+-Wconversion -Wno-deprecated-declarations @gol
+-Wdisabled-optimization -Wdiv-by-zero -Werror @gol
-Wfloat-equal -Wformat -Wformat=2 @gol
-Wformat-nonliteral -Wformat-security @gol
-Wimplicit -Wimplicit-int @gol
@item Debugging Options
@xref{Debugging Options,,Options for Debugging Your Program or GCC}.
@gccoptlist{
--a -ax -d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol
+-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol
-fdump-unnumbered -fdump-translation-unit@r{[}-@var{n}@r{]} @gol
-fdump-class-hierarchy@r{[}-@var{n}@r{]} @gol
--fdump-ast-original@r{[}-@var{n}@r{]} -fdump-ast-optimized@r{[}-@var{n}@r{]} @gol
--fdump-ast-inlined@r{[}-@var{n}@r{]} @gol
+-fdump-tree-original@r{[}-@var{n}@r{]} -fdump-tree-optimized@r{[}-@var{n}@r{]} @gol
+-fdump-tree-inlined@r{[}-@var{n}@r{]} @gol
-fmem-report -fpretend-float @gol
-fprofile-arcs -ftest-coverage -ftime-report @gol
-g -g@var{level} -gcoff -gdwarf -gdwarf-1 -gdwarf-1+ -gdwarf-2 @gol
--ggdb -gstabs -gstabs+ -gxcoff -gxcoff+ @gol
+-ggdb -gstabs -gstabs+ -gvms -gxcoff -gxcoff+ @gol
-p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol
-print-multi-directory -print-multi-lib @gol
-print-prog-name=@var{program} -print-search-dirs -Q @gol
@gccoptlist{
-falign-functions=@var{n} -falign-jumps=@var{n} @gol
-falign-labels=@var{n} -falign-loops=@var{n} @gol
--fbranch-probabilities -fcaller-saves @gol
+-fbranch-probabilities -fcaller-saves -fcprop-registers @gol
-fcse-follow-jumps -fcse-skip-blocks -fdata-sections @gol
-fdelayed-branch -fdelete-null-pointer-checks @gol
-fexpensive-optimizations -ffast-math -ffloat-store @gol
-fforce-addr -fforce-mem -ffunction-sections @gol
-fgcse -fgcse-lm -fgcse-sm @gol
-finline-functions -finline-limit=@var{n} -fkeep-inline-functions @gol
--fkeep-static-consts -fmove-all-movables @gol
--fno-default-inline -fno-defer-pop @gol
+-fkeep-static-consts -fmerge-constants -fmerge-all-constants @gol
+-fmove-all-movables -fno-default-inline -fno-defer-pop @gol
-fno-function-cse -fno-guess-branch-probability @gol
-fno-inline -fno-math-errno -fno-peephole -fno-peephole2 @gol
-funsafe-math-optimizations -fno-trapping-math @gol
+-fno-zero-initialized-in-bss @gol
-fomit-frame-pointer -foptimize-register-move @gol
--foptimize-sibling-calls -freduce-all-givs @gol
--fregmove -frename-registers @gol
+-foptimize-sibling-calls -fprefetch-loop-arrays @gol
+-freduce-all-givs -fregmove -frename-registers @gol
-frerun-cse-after-loop -frerun-loop-opt @gol
-fschedule-insns -fschedule-insns2 @gol
--fsingle-precision-constant -fssa -fssa-dce @gol
+-fsingle-precision-constant -fssa -fssa-ccp -fssa-dce @gol
-fstrength-reduce -fstrict-aliasing -fthread-jumps -ftrapv @gol
-funroll-all-loops -funroll-loops @gol
--param @var{name}=@var{value}
@item Machine Dependent Options
@xref{Submodel Options,,Hardware Models and Configurations}.
+
@emph{M680x0 Options}
@gccoptlist{
-m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol
@emph{M32R/D Options}
@gccoptlist{
--mcode-model=@var{model-type} -msdata=@var{sdata-type} @gol
+-m32rx -m32r -mcode-model=@var{model-type} -msdata=@var{sdata-type} @gol
-G @var{num}}
@emph{M88K Options}
-mtune=@var{cpu-type} @gol
-mpower -mno-power -mpower2 -mno-power2 @gol
-mpowerpc -mpowerpc64 -mno-powerpc @gol
+-maltivec -mno-altivec @gol
-mpowerpc-gpopt -mno-powerpc-gpopt @gol
-mpowerpc-gfxopt -mno-powerpc-gfxopt @gol
-mnew-mnemonics -mold-mnemonics @gol
--mfull-toc -mminimal-toc -mno-fop-in-toc -mno-sum-in-toc @gol
--m64 -m32 -mxl-call -mno-xl-call -mthreads -mpe @gol
+-mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc @gol
+-m64 -m32 -mxl-call -mno-xl-call -mpe @gol
-msoft-float -mhard-float -mmultiple -mno-multiple @gol
-mstring -mno-string -mupdate -mno-update @gol
-mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol
-mstrict-align -mno-strict-align -mrelocatable @gol
-mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol
-mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol
--mcall-aix -mcall-sysv -mprototype -mno-prototype @gol
+-mcall-aix -mcall-sysv -mcall-netbsd @gol
+-maix-struct-return -msvr4-struct-return
+-mabi=altivec @gol
+-mprototype -mno-prototype @gol
-msim -mmvme -mads -myellowknife -memb -msdata @gol
--msdata=@var{opt} -mvxworks -G @var{num}}
+-msdata=@var{opt} -mvxworks -G @var{num} -pthread}
@emph{RT Options}
@gccoptlist{
@emph{MIPS Options}
@gccoptlist{
--mabicalls -mcpu=@var{cpu-type} @gol
--membedded-data -muninit-const-in-rodata @gol
--membedded-pic -mfp32 -mfp64 -mgas -mgp32 -mgp64 @gol
+-mabicalls -march=@var{cpu-type} -mtune=@var{cpu=type} @gol
+-mcpu=@var{cpu-type} -membedded-data -muninit-const-in-rodata @gol
+-membedded-pic -mfp32 -mfp64 -mfused-madd -mno-fused-madd @gol
+-mgas -mgp32 -mgp64 @gol
-mgpopt -mhalf-pic -mhard-float -mint64 -mips1 @gol
-mips2 -mips3 -mips4 -mlong64 -mlong32 -mlong-calls -mmemcpy @gol
-mmips-as -mmips-tfile -mno-abicalls @gol
-m4650 -msingle-float -mmad @gol
-mstats -EL -EB -G @var{num} -nocpp @gol
-mabi=32 -mabi=n32 -mabi=64 -mabi=eabi @gol
--mfix7000 -mno-crt0}
+-mfix7000 -mno-crt0 -mflush-func=@var{func} -mno-flush-func}
-@emph{i386 Options}
+@emph{i386 and x86-64 Options}
@gccoptlist{
--mcpu=@var{cpu-type} -march=@var{cpu-type} @gol
--mintel-syntax -mieee-fp -mno-fancy-math-387 @gol
+-mcpu=@var{cpu-type} -march=@var{cpu-type} -mfpmath=@var{unit} @gol
+-masm=@var{dialect} -mno-fancy-math-387 @gol
-mno-fp-ret-in-387 -msoft-float -msvr3-shlib @gol
-mno-wide-multiply -mrtd -malign-double @gol
-mpreferred-stack-boundary=@var{num} @gol
+-mmmx -msse -msse2 -msse-math -m3dnow @gol
-mthreads -mno-align-stringops -minline-all-stringops @gol
-mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol
--m96bit-long-double -mregparm=@var{num} -momit-leaf-frame-pointer}
+-m96bit-long-double -mregparm=@var{num} -momit-leaf-frame-pointer @gol
+-mno-red-zone@gol
+-m32 -m64}
@emph{HPPA Options}
@gccoptlist{
@emph{DEC Alpha Options}
@gccoptlist{
--mfp-regs -mno-fp-regs -mno-soft-float -msoft-float @gol
--malpha-as -mgas @gol
+-mno-fp-regs -msoft-float -malpha-as -mgas @gol
-mieee -mieee-with-inexact -mieee-conformant @gol
-mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol
-mtrap-precision=@var{mode} -mbuild-constants @gol
--mcpu=@var{cpu-type} @gol
--mbwx -mno-bwx -mcix -mno-cix -mmax -mno-max @gol
+-mcpu=@var{cpu-type} -mtune=@var{cpu-type} @gol
+-mbwx -mmax -mfix -mcix @gol
+-mfloat-vax -mfloat-ieee @gol
+-mexplicit-relocs -msmall-data -mlarge-data @gol
-mmemory-latency=@var{time}}
+@emph{DEC Alpha/VMS Options}
+@gccoptlist{
+-mvms-return-codes}
+
@emph{Clipper Options}
@gccoptlist{
-mc300 -mc400}
@gccoptlist{
-m1 -m2 -m3 -m3e @gol
-m4-nofpu -m4-single-only -m4-single -m4 @gol
+-m5-64media -m5-64media-nofpu @gol
+-m5-32media -m5-32media-nofpu @gol
+-m5-compact -m5-compact-nofpu @gol
-mb -ml -mdalign -mrelax @gol
-mbigtable -mfmovd -mhitachi -mnomacsave @gol
-mieee -misize -mpadstruct -mspace @gol
-mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol
-mlittle-endian -mbig-endian -m210 -m340 -mstack-increment}
+@emph{MMIX Options}
+@gccoptlist{
+-mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu @gol
+-mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols @gol
+-melf -mbranch-predict -mno-branch-predict -mbase-addresses @gol
+-mno-base-addresses}
+
@emph{IA-64 Options}
@gccoptlist{
-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol
-minline-divide-max-throughput -mno-dwarf2-asm @gol
-mfixed-range=@var{register-range}}
+@emph{D30V Options}
+@gccoptlist{
+-mextmem -mextmemory -monchip -mno-asm-optimize -masm-optimize @gol
+-mbranch-cost=@var{n} -mcond-exec=@var{n}}
+
+@emph{S/390 and zSeries Options}
+@gccoptlist{
+-mhard-float -msoft-float -mbackchain -mno-backchain @gol
+-msmall-exec -mno-small-exec -mmvcle -mno-mvcle @gol
+-m64 -m31 -mdebug -mno-debug}
+
+@emph{CRIS Options}
+@gccoptlist{
+-mcpu=@var{cpu} -march=@var{cpu} -mtune=@var{cpu} @gol
+-mmax-stack-frame=@var{n} -melinux-stacksize=@var{n} @gol
+-metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects @gol
+-mstack-align -mdata-align -mconst-align @gol
+-m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt @gol
+-melf -maout -melinux -mlinux -sim -sim2}
+
+@emph{PDP-11 Options}
+@gccoptlist{
+-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol
+-mbcopy -mbcopy-builtin -mint32 -mno-int16 @gol
+-mint16 -mno-int32 -mfloat32 -mno-float64 @gol
+-mfloat64 -mno-float32 -mabshi -mno-abshi @gol
+-mbranch-expensive -mbranch-cheap @gol
+-msplit -mno-split -munix-asm -mdec-asm}
+
+@emph{Xstormy16 Options}
+@gccoptlist{
+-msim}
+
+@emph{Xtensa Options}
+@gccoptlist{
+-mbig-endian -mlittle-endian @gol
+-mdensity -mno-density @gol
+-mmac16 -mno-mac16 @gol
+-mmul16 -mno-mul16 @gol
+-mmul32 -mno-mul32 @gol
+-mnsa -mno-nsa @gol
+-mminmax -mno-minmax @gol
+-msext -mno-sext @gol
+-mbooleans -mno-booleans @gol
+-mhard-float -msoft-float @gol
+-mfused-madd -mno-fused-madd @gol
+-mserialize-volatile -mno-serialize-volatile @gol
+-mtext-section-literals -mno-text-section-literals @gol
+-mtarget-align -mno-target-align @gol
+-mlongcalls -mno-longcalls}
+
@item Code Generation Options
@xref{Code Gen Options,,Options for Code Generation Conventions}.
@gccoptlist{
-fcall-saved-@var{reg} -fcall-used-@var{reg} @gol
-ffixed-@var{reg} -fexceptions @gol
-fnon-call-exceptions -funwind-tables @gol
+-fasynchronous-unwind-tables @gol
-finhibit-size-directive -finstrument-functions @gol
--fcheck-memory-usage -fprefix-function-name @gol
-fno-common -fno-ident -fno-gnu-linker @gol
-fpcc-struct-return -fpic -fPIC @gol
-freg-struct-return -fshared-data -fshort-enums @gol
@c @var{file}.zip
@c @var{file}.jar
+@item @var{file}.ads
+Ada source code file which 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 @dfn{specs}.
+
+@itemx @var{file}.adb
+Ada source code file containing a library unit body (a subprogram or
+package body). Such files are also called @dfn{bodies}.
+
@c GCC also knows about some suffixes for languages not yet included:
-@c Ada:
-@c @var{file}.ads
-@c @var{file}.adb
-@c @var{file}.ada
@c Pascal:
@c @var{file}.p
@c @var{file}.pas
c++ c++-cpp-output
objective-c objc-cpp-output
assembler assembler-with-cpp
+ada
+chill
f77 f77-cpp-input ratfor
-java chill
+java
@end example
-@c Also f77-version, for internal use only.
@item -x none
Turn off any specification of a language, so that subsequent files are
Default, ISO C89 plus GNU extensions (including some C99 features).
@item gnu99
-@itemx gnu9x
+@item gnu9x
ISO C99 plus GNU extensions. When ISO C99 is fully implemented in GCC,
this will become the default. The name @samp{gnu9x} is deprecated.
@code{inline} is a standard keyword in ISO C99.
@item -fno-builtin
+@itemx -fno-builtin-@var{function} @r{(C and Objective-C only)}
@opindex fno-builtin
@cindex built-in functions
Don't recognize built-in functions that do not begin with
built-in functions to implement many functions (like
@code{std::strchr}), so that you automatically get efficient code.
+With the @option{-fno-builtin-@var{function}} option, not available
+when compiling C++, only the built-in function @var{function} is
+disabled. @var{function} must not begin with @samp{__builtin_}. If a
+function is named this is not built-in in this version of GCC, this
+option is ignored. There is no corresponding
+@option{-fbuiltin-@var{function}} option; if you wish to enable
+built-in functions selectively when using @option{-fno-builtin} or
+@option{-ffreestanding}, you may define macros such as:
+
+@smallexample
+#define abs(n) __builtin_abs ((n))
+#define strcpy(d, s) __builtin_strcpy ((d), (s))
+@end smallexample
+
@item -fhosted
@opindex fhosted
@cindex hosted environment
@cindex traditional C language
@cindex C language, traditional
@item -traditional
-@opindex traditional
-Attempt to support some aspects of traditional C compilers.
-Specifically:
-
-@itemize @bullet
-@item
-All @code{extern} declarations take effect globally even if they
-are written inside of a function definition. This includes implicit
-declarations of functions.
-
-@item
-The newer keywords @code{typeof}, @code{inline}, @code{signed}, @code{const}
-and @code{volatile} are not recognized. (You can still use the
-alternative keywords such as @code{__typeof__}, @code{__inline__}, and
-so on.)
-
-@item
-Comparisons between pointers and integers are always allowed.
-
-@item
-Integer types @code{unsigned short} and @code{unsigned char} promote
-to @code{unsigned int}.
-
-@item
-Out-of-range floating point literals are not an error.
-
-@item
-Certain constructs which ISO regards as a single invalid preprocessing
-number, such as @samp{0xe-0xd}, are treated as expressions instead.
-
-@item
-String ``constants'' are not necessarily constant; they are stored in
-writable space, and identical looking constants are allocated
-separately. (This is the same as the effect of
-@option{-fwritable-strings}.)
-
-@cindex @code{longjmp} and automatic variables
-@item
-All automatic variables not declared @code{register} are preserved by
-@code{longjmp}. Ordinarily, GNU C follows ISO C: automatic variables
-not declared @code{volatile} may be clobbered.
-
-@item
-@cindex @samp{\x}
-@cindex @samp{\a}
-@cindex escape sequences, traditional
-The character escape sequences @samp{\x} and @samp{\a} evaluate as the
-literal characters @samp{x} and @samp{a} respectively. Without
-@w{@option{-traditional}}, @samp{\x} is a prefix for the hexadecimal
-representation of a character, and @samp{\a} produces a bell.
-@end itemize
-
-You may wish to use @option{-fno-builtin} as well as @option{-traditional}
-if your program uses names that are normally GNU C built-in functions for
-other purposes of its own.
-
-You cannot use @option{-traditional} if you include any header files that
-rely on ISO C features. Some vendors are starting to ship systems with
-ISO C header files and you cannot use @option{-traditional} on such
-systems to compile files that include any system headers.
-
-The @option{-traditional} option also enables @option{-traditional-cpp},
-which is described next.
-
-@item -traditional-cpp
+@itemx -traditional-cpp
@opindex traditional-cpp
-Attempt to support some aspects of traditional C preprocessors.
-Specifically:
-
-@itemize @bullet
-@item
-Comments convert to nothing at all, rather than to a space. This allows
-traditional token concatenation.
-
-@item
-In a preprocessing directive, the @samp{#} symbol must appear as the first
-character of a line.
-
-@item
-Macro arguments are recognized within string constants in a macro
-definition (and their values are stringified, though without additional
-quote marks, when they appear in such a context). The preprocessor
-always considers a string constant to end at a newline.
-
-@item
-@cindex detecting @w{@option{-traditional}}
-The predefined macro @code{__STDC__} is not defined when you use
-@option{-traditional}, but @code{__GNUC__} is (since the GNU extensions
-which @code{__GNUC__} indicates are not affected by
-@option{-traditional}). If you need to write header files that work
-differently depending on whether @option{-traditional} is in use, by
-testing both of these predefined macros you can distinguish four
-situations: GNU C, traditional GNU C, other ISO C compilers, and other
-old C compilers. The predefined macro @code{__STDC_VERSION__} is also
-not defined when you use @option{-traditional}. @xref{Standard
-Predefined,,Standard Predefined Macros,cpp.info,The C Preprocessor},
-for more discussion of these and other predefined macros.
-
-@item
-@cindex string constants vs newline
-@cindex newline vs string constants
-The preprocessor considers a string constant to end at a newline (unless
-the newline is escaped with @samp{\}). (Without @w{@option{-traditional}},
-string constants can contain the newline character as typed.)
-@end itemize
+@opindex traditional
+Formerly, these options caused GCC to attempt to emulate a pre-standard
+C compiler. They are now only supported with the @option{-E} switch.
+The preprocessor continues to support a pre-standard mode. See the GNU
+CPP manual for details.
@item -fcond-mismatch
@opindex fcond-mismatch
default, such a bit-field is signed, because this is consistent: the
basic integer types such as @code{int} are signed types.
-However, when @option{-traditional} is used, bit-fields are all unsigned
-no matter what.
-
@item -fwritable-strings
@opindex fwritable-strings
Store string constants in the writable data segment and don't uniquize
them. This is for compatibility with old programs which assume they can
-write into string constants. The option @option{-traditional} also has
-this effect.
+write into string constants.
Writing into string constants is a very bad idea; ``constants'' should
be constant.
-@item -fallow-single-precision
-@opindex fallow-single-precision
-Do not promote single precision math operations to double precision,
-even when compiling with @option{-traditional}.
-
-Traditional K&R C promotes all floating point operations to double
-precision, regardless of the sizes of the operands. On the
-architecture for which you are compiling, single precision may be faster
-than double precision. If you must use @option{-traditional}, but want
-to use single precision operations when the operands are single
-precision, use this option. This option has no effect when compiling
-with ISO or GNU C conventions (the default).
-
@item -fshort-wchar
@opindex fshort-wchar
Override the underlying type for @samp{wchar_t} to be @samp{short
@item -fexternal-templates
@opindex fexternal-templates
-Cause template instantiations to obey @samp{#pragma interface} and
-@samp{implementation}; template instances are emitted or not according
+
+Cause @samp{#pragma interface} and @samp{implementation} to apply to
+template instantiation; template instances are emitted or not according
to the location of the template definition. @xref{Template
Instantiation}, for more information.
@item -falt-external-templates
@opindex falt-external-templates
-Similar to @option{-fexternal-templates}, but template instances are emitted or
-not according to the place where they are first instantiated.
+Similar to @option{-fexternal-templates}, but template instances are
+emitted or not according to the place where they are first instantiated.
@xref{Template Instantiation}, for more information.
This option is deprecated.
word as an identifier. You can use the keyword @code{__typeof__} instead.
@option{-ansi} implies @option{-fno-gnu-keywords}.
-@item -fno-honor-std
-@opindex fno-honor-std
-Ignore @code{namespace std}, instead of treating it as a real namespace.
-With this switch, the compiler will ignore
-@code{namespace-declarations}, @code{using-declarations},
-@code{using-directives}, and @code{namespace-names}, if they involve
-@code{std}.
-
-This option is only useful if you have manually compiled the C++
-run-time library with the same switch. Otherwise, your programs will
-not link. The use of this option is not recommended, and the option may
-be removed from a future version of G++.
-
@item -fno-implicit-templates
@opindex fno-implicit-templates
Never emit code for non-inline templates which are instantiated
@item -frepo
@opindex frepo
-Enable automatic template instantiation. This option also implies
-@option{-fno-implicit-templates}. @xref{Template Instantiation}, for more
-information.
+Enable automatic template instantiation at link time. This option also
+implies @option{-fno-implicit-templates}. @xref{Template
+Instantiation}, for more information.
@item -fno-rtti
@opindex fno-rtti
@table @gcctabopt
@item -Weffc++ @r{(C++ only)}
@opindex Weffc++
-Warn about violations of various style guidelines from Scott Meyers'
-@cite{Effective C++} books. If you use this option, you should be aware
-that the standard library headers do not obey all of these guidelines;
-you can use @samp{grep -v} to filter out those warnings.
+Warn about violations of the following style guidelines from Scott Meyers'
+@cite{Effective C++} book:
+
+@itemize @bullet
+@item
+Item 11: Define a copy constructor and an assignment operator for classes
+with dynamically allocated memory.
+
+@item
+Item 12: Prefer initialization to assignment in constructors.
+
+@item
+Item 14: Make destructors virtual in base classes.
+
+@item
+Item 15: Have @code{operator=} return a reference to @code{*this}.
+
+@item
+Item 23: Don't try to return a reference when you must return an object.
+
+@end itemize
+
+and about violations of the following style guidelines from Scott Meyers'
+@cite{More Effective C++} book:
+
+@itemize @bullet
+@item
+Item 6: Distinguish between prefix and postfix forms of increment and
+decrement operators.
+
+@item
+Item 7: Never overload @code{&&}, @code{||}, or @code{,}.
+
+@end itemize
+
+If you use this option, you should be aware that the standard library
+headers do not obey all of these guidelines; you can use @samp{grep -v}
+to filter out those warnings.
@item -Wno-deprecated @r{(C++ only)}
@opindex Wno-deprecated
@item -Wold-style-cast @r{(C++ only)}
@opindex Wold-style-cast
-Warn if an old-style (C-style) cast is used within a C++ program. The
-new-style casts (@samp{static_cast}, @samp{reinterpret_cast}, and
-@samp{const_cast}) are less vulnerable to unintended effects, and much
-easier to grep for.
+Warn if an old-style (C-style) cast to a non-void type is used within
+a C++ program. The new-style casts (@samp{static_cast},
+@samp{reinterpret_cast}, and @samp{const_cast}) are less vulnerable to
+unintended effects, and much easier to grep for.
@item -Woverloaded-virtual @r{(C++ only)}
@opindex Woverloaded-virtual
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
-behaviour.
+behavior.
@item -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
+prefix) for physical lines that result from the process of breaking
a message which is too long to fit on a single line.
@end table
@code{printf} or @code{scanf} format function. The C standard specifies
that such arguments are ignored.
+Where the unused arguments lie between used arguments that are
+specified with @samp{$} operand number specifications, normally
+warnings are still given, since the implementation could not know what
+type to pass to @code{va_arg} to skip the unused arguments. However,
+in the case of @code{scanf} formats, this option will suppress the
+warning if the unused arguments are all pointers, since the Single
+Unix Specification says that such unused arguments are allowed.
+
@item -Wformat-nonliteral
@opindex Wformat-nonliteral
If @option{-Wformat} is specified, also warn if the format string is not a
int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @};
@end smallexample
-@item -Wmultichar
-@opindex Wmultichar
-Warn if a multicharacter constant (@samp{'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.
-
@item -Wparentheses
@opindex Wparentheses
Warn if parentheses are omitted in certain contexts, such
The present implementation of this option only works for C programs. A
future implementation may also work for C++ programs.
-There is some controversy over the precise meaning of the sequence point
-rules in subtle cases. Links to papers with alternative formal definitions
-and other related discussions may be found on our readings page
+The C 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 our readings page, at
@w{@uref{http://gcc.gnu.org/readings.html}}.
@item -Wreturn-type
that are easy to avoid (or modify to prevent the warning), even in
conjunction with macros.
+@item -Wdiv-by-zero
+@opindex Wno-div-by-zero
+@opindex Wdiv-by-zero
+Warn about compile-time integer division by zero. This is default. To
+inhibit the warning messages, use @option{-Wno-div-by-zero}. Floating
+point division by zero is not warned about, as it can be a legitimate
+way of obtaining infinities and NaNs.
+
+@item -Wmultichar
+@opindex Wno-multichar
+@opindex Wmultichar
+Warn if a multicharacter constant (@samp{'FOOF'}) is used. This is
+default. To inhibit the warning messages, use @option{-Wno-multichar}.
+Usually they indicate a typo in the user's code, as they have
+implementation-defined values, and should not be used in portable code.
+
@item -Wsystem-headers
@opindex Wsystem-headers
@cindex warnings from system headers
understands but would ignore because the @samp{#} does not appear as the
first character on the line. It also suggests you hide directives like
@samp{#pragma} not understood by traditional C by indenting them. Some
-traditional implementations would not recognise @samp{#elif}, so it
+traditional implementations would not recognize @samp{#elif}, so it
suggests avoiding it altogether.
@item
appropriate may not be detected. This option has no effect unless
@option{-Wformat} is enabled (possibly by @option{-Wall}).
+@item -Wno-deprecated-declarations
+@opindex Wno-deprecated-declarations
+Do not warn about uses of functions, variables, and types marked as
+deprecated by using the @code{deprecated} attribute.
+(@pxref{Function Attributes}, @pxref{Variable Attributes},
+@pxref{Type Attributes}.)
+
@item -Wpacked
@opindex Wpacked
Warn if a structure is given the packed attribute, but the packed
version of a program there is often substantial code which checks
correct functioning of the program and is, hopefully, unreachable
because the program does work. Another common use of unreachable
-code is to provide behaviour which is selectable at compile-time.
+code is to provide behavior which is selectable at compile-time.
@item -Winline
@opindex Winline
crash or
refuse to read the program. If you want to control for certain whether
to generate the extra information, use @option{-gstabs+}, @option{-gstabs},
-@option{-gxcoff+}, @option{-gxcoff}, @option{-gdwarf-1+}, or @option{-gdwarf-1}
-(see below).
+@option{-gxcoff+}, @option{-gxcoff}, @option{-gdwarf-1+}, @option{-gdwarf-1},
+or @option{-gvms} (see below).
Unlike most other C compilers, GCC allows you to use @option{-g} with
@option{-O}. The shortcuts taken by optimized code may occasionally
Produce debugging information in DWARF version 2 format (if that is
supported). This is the format used by DBX on IRIX 6.
+@item -gvms
+@opindex gvms
+Produce debugging information in VMS debug format (if that is
+supported). This is the format used by DEBUG on VMS systems.
+
@item -g@var{level}
@itemx -ggdb@var{level}
@itemx -gstabs@var{level}
@itemx -gxcoff@var{level}
@itemx -gdwarf@var{level}
@itemx -gdwarf-2@var{level}
+@itemx -gvms@var{level}
Request debugging information and also use @var{level} to specify how
much information. The default level is 2.
Makes the compiler print some statistics about permanent memory
allocation when it finishes.
-@item -ax
-@opindex ax
-Generate extra code to profile basic blocks. Your executable will
-produce output that is a superset of that produced when @option{-a} is
-used. Additional output is the source and target address of the basic
-blocks where a jump takes place, the number of times a jump is executed,
-and (optionally) the complete sequence of basic blocks being executed.
-The output is appended to file @file{bb.out}.
-
-You can examine different profiling aspects without recompilation. Your
-executable will read a list of function names from file @file{bb.in}.
-Profiling starts when a function on the list is entered and stops when
-that invocation is exited. To exclude a function from profiling, prefix
-its name with @samp{-}. If a function name is not unique, you can
-disambiguate it by writing it in the form
-@samp{/path/filename.d:functionname}. Your executable will write the
-available paths and filenames in file @file{bb.out}.
-
-Several function names have a special meaning:
-@table @code
-@item __bb_jumps__
-Write source, target and frequency of jumps to file @file{bb.out}.
-@item __bb_hidecall__
-Exclude function calls from frequency count.
-@item __bb_showret__
-Include function returns in frequency count.
-@item __bb_trace__
-Write the sequence of basic blocks executed to file @file{bbtrace.gz}.
-The file will be compressed using the program @samp{gzip}, which must
-exist in your @env{PATH}. On systems without the @samp{popen}
-function, the file will be named @file{bbtrace} and will not be
-compressed. @strong{Profiling for even a few seconds on these systems
-will produce a very large file.} Note: @code{__bb_hidecall__} and
-@code{__bb_showret__} will not affect the sequence written to
-@file{bbtrace.gz}.
-@end table
-
-Here's a short example using different profiling parameters
-in file @file{bb.in}. Assume function @code{foo} consists of basic blocks
-1 and 2 and is called twice from block 3 of function @code{main}. After
-the calls, block 3 transfers control to block 4 of @code{main}.
-
-With @code{__bb_trace__} and @code{main} contained in file @file{bb.in},
-the following sequence of blocks is written to file @file{bbtrace.gz}:
-0 3 1 2 1 2 4. The return from block 2 to block 3 is not shown, because
-the return is to a point inside the block and not to the top. The
-block address 0 always indicates, that control is transferred
-to the trace from somewhere outside the observed functions. With
-@samp{-foo} added to @file{bb.in}, the blocks of function
-@code{foo} are removed from the trace, so only 0 3 4 remains.
-
-With @code{__bb_jumps__} and @code{main} contained in file @file{bb.in},
-jump frequencies will be written to file @file{bb.out}. The
-frequencies are obtained by constructing a trace of blocks
-and incrementing a counter for every neighbouring pair of blocks
-in the trace. The trace 0 3 1 2 1 2 4 displays the following
-frequencies:
-
-@example
-Jump from block 0x0 to block 0x3 executed 1 time(s)
-Jump from block 0x3 to block 0x1 executed 1 time(s)
-Jump from block 0x1 to block 0x2 executed 2 time(s)
-Jump from block 0x2 to block 0x1 executed 1 time(s)
-Jump from block 0x2 to block 0x4 executed 1 time(s)
-@end example
-
-With @code{__bb_hidecall__}, control transfer due to call instructions
-is removed from the trace, that is the trace is cut into three parts: 0
-3 4, 0 1 2 and 0 1 2. With @code{__bb_showret__}, control transfer due
-to return instructions is added to the trace. The trace becomes: 0 3 1
-2 3 1 2 3 4. Note, that this trace is not the same, as the sequence
-written to @file{bbtrace.gz}. It is solely used for counting jump
-frequencies.
-
@item -fprofile-arcs
@opindex fprofile-arcs
-Instrument @dfn{arcs} during compilation. 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.
-
-Since not every arc in the program must be instrumented, programs
-compiled with this option run faster than programs compiled with
-@option{-a}, which adds instrumentation code to every basic block in the
-program. The tradeoff: since @code{gcov} does not have
-execution counts for all branches, it must start with the execution
-counts for the instrumented branches, and then iterate over the program
-flow graph until the entire graph has been solved. Hence, @code{gcov}
-runs a little more slowly than a program which uses information from
-@option{-a}.
-
-@option{-fprofile-arcs} also makes it possible to estimate branch
-probabilities, and to calculate basic block execution counts. In
-general, basic block execution counts do not give enough information to
-estimate all branch probabilities. When the compiled program exits, it
-saves the arc execution counts to a file called
-@file{@var{sourcename}.da}. Use the compiler option
+Instrument @dfn{arcs} during compilation to generate coverage data
+or for profile-directed block ordering. During execution the program
+records how many times each branch is executed and how many times it is
+taken. When the compiled program exits it saves this data to a file
+called @file{@var{sourcename}.da} for each source file.
+
+For profile-directed block ordering, compile the program with
+@option{-fprofile-arcs} plus optimization and code generation options,
+generate the arc profile information by running the program on a
+selected workload, and then compile the program again with the same
+optimization and code generation options plus
@option{-fbranch-probabilities} (@pxref{Optimize Options,,Options that
-Control Optimization}) when recompiling, to optimize using estimated
-branch probabilities.
+Control Optimization}).
+
+The other use of @option{-fprofile-arcs} is for use with @code{gcov},
+when it is used with the @option{-ftest-coverage} option. GCC
+supports two methods of determining code coverage: the options that
+support @code{gcov}, and options @option{-a} and @option{-ax}, which
+write information to text files. The options that support @code{gcov}
+do not need to instrument every arc in the program, so a program compiled
+with them runs faster than a program compiled with @option{-a}, which
+adds instrumentation code to every basic block in the program. The
+tradeoff: since @code{gcov} does not have execution counts for all
+branches, it must start with the execution counts for the instrumented
+branches, and then iterate over the program flow graph until the entire
+graph has been solved. Hence, @code{gcov} runs a little more slowly than
+a program which uses information from @option{-a} and @option{-ax}.
+
+With @option{-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.
+
+This option makes it possible to estimate branch probabilities and to
+calculate basic block execution counts. In general, basic block
+execution counts as provided by @option{-a} do not give enough
+information to estimate all branch probabilities.
@need 2000
@item -ftest-coverage
A list of all arcs in the program flow graph. This allows @code{gcov}
to reconstruct the program flow graph, so that it can compute all basic
block and arc execution counts from the information in the
-@code{@var{sourcename}.da} file (this last file is the output from
-@option{-fprofile-arcs}).
+@code{@var{sourcename}.da} file.
@end table
+Use @option{-ftest-coverage} with @option{-fprofile-arcs}; the latter
+option adds instrumentation to the program, which then writes
+execution counts to another data file:
+
+@table @gcctabopt
+@item @var{sourcename}.da
+Runtime arc execution counts, used in conjunction with the arc
+information in the file @code{@var{sourcename}.bbg}.
+@end table
+
+Coverage data will map better to the source files if
+@option{-ftest-coverage} is used without optimization.
+
@item -d@var{letters}
@opindex d
Says to make debugging dumps during compilation at times specified by
Annotate the assembler output with miscellaneous debugging information.
@item b
@opindex db
-Dump after computing branch probabilities, to @file{@var{file}.13.bp}.
+Dump after computing branch probabilities, to @file{@var{file}.15.bp}.
@item B
@opindex dB
-Dump after block reordering, to @file{@var{file}.27.bbro}.
+Dump after block reordering, to @file{@var{file}.30.bbro}.
@item c
@opindex dc
-Dump after instruction combination, to the file @file{@var{file}.15.combine}.
+Dump after instruction combination, to the file @file{@var{file}.17.combine}.
@item C
@opindex dC
-Dump after the first if conversion, to the file @file{@var{file}.16.ce}.
+Dump after the first if conversion, to the file @file{@var{file}.18.ce}.
@item d
@opindex dd
-Dump after delayed branch scheduling, to @file{@var{file}.30.dbr}.
+Dump after delayed branch scheduling, to @file{@var{file}.32.dbr}.
@item D
@opindex dD
Dump all macro definitions, at the end of preprocessing, in addition to
@item e
@opindex de
Dump after SSA optimizations, to @file{@var{file}.04.ssa} and
-@file{@var{file}.06.ussa}.
+@file{@var{file}.07.ussa}.
@item E
@opindex dE
-Dump after the second if conversion, to @file{@var{file}.25.ce2}.
+Dump after the second if conversion, to @file{@var{file}.27.ce2}.
@item f
@opindex df
-Dump after life analysis, to @file{@var{file}.14.life}.
+Dump after life analysis, to @file{@var{file}.16.life}.
@item F
@opindex dF
-Dump after purging @code{ADDRESSOF} codes, to @file{@var{file}.08.addressof}.
+Dump after purging @code{ADDRESSOF} codes, to @file{@var{file}.10.addressof}.
@item g
@opindex dg
-Dump after global register allocation, to @file{@var{file}.20.greg}.
+Dump after global register allocation, to @file{@var{file}.22.greg}.
@item h
@opindex dh
Dump after finalization of EH handling code, to @file{@var{file}.02.eh}.
-@item o
+@item k
+@opindex dk
+Dump after reg-to-stack conversion, to @file{@var{file}.29.stack}.
@item o
@opindex do
-Dump after post-reload CSE and other optimizations, to @file{@var{file}.21.postreload}.
+Dump after post-reload optimizations, to @file{@var{file}.23.postreload}.
@item G
@opindex dG
-Dump after GCSE, to @file{@var{file}.09.gcse}.
+Dump after GCSE, to @file{@var{file}.11.gcse}.
@item i
@opindex di
Dump after sibling call optimizations, to @file{@var{file}.01.sibling}.
@item j
@opindex dj
Dump after the first jump optimization, to @file{@var{file}.03.jump}.
-@item J
-@opindex dJ
-Dump after the last jump optimization, to @file{@var{file}.28.jump2}.
@item k
@opindex dk
-Dump after conversion from registers to stack, to @file{@var{file}.31.stack}.
+Dump after conversion from registers to stack, to @file{@var{file}.33.stack}.
@item l
@opindex dl
-Dump after local register allocation, to @file{@var{file}.19.lreg}.
+Dump after local register allocation, to @file{@var{file}.21.lreg}.
@item L
@opindex dL
-Dump after loop optimization, to @file{@var{file}.10.loop}.
+Dump after loop optimization, to @file{@var{file}.12.loop}.
@item M
@opindex dM
Dump after performing the machine dependent reorganisation pass, to
-@file{@var{file}.29.mach}.
+@file{@var{file}.31.mach}.
@item n
@opindex dn
-Dump after register renumbering, to @file{@var{file}.24.rnreg}.
+Dump after register renumbering, to @file{@var{file}.26.rnreg}.
@item N
@opindex dN
-Dump after the register move pass, to @file{@var{file}.17.regmove}.
+Dump after the register move pass, to @file{@var{file}.19.regmove}.
@item r
@opindex dr
Dump after RTL generation, to @file{@var{file}.00.rtl}.
@item R
@opindex dR
-Dump after the second instruction scheduling pass, to
-@file{@var{file}.26.sched2}.
+Dump after the second scheduling pass, to @file{@var{file}.28.sched2}.
@item s
@opindex ds
Dump after CSE (including the jump optimization that sometimes follows
-CSE), to @file{@var{file}.07.cse}.
+CSE), to @file{@var{file}.09.cse}.
@item S
@opindex dS
-Dump after the first instruction scheduling pass, to
-@file{@var{file}.18.sched}.
+Dump after the first scheduling pass, to @file{@var{file}.20.sched}.
@item t
@opindex dt
Dump after the second CSE pass (including the jump optimization that
-sometimes follows CSE), to @file{@var{file}.11.cse2}.
+sometimes follows CSE), to @file{@var{file}.13.cse2}.
+@item u
+@opindex du
+Dump after null pointer ellimination pass ti @file{@var{file}.08.null}.
@item w
@opindex dw
-Dump after the second flow pass, to @file{@var{file}.22.flow2}.
+Dump after the second flow pass, to @file{@var{file}.24.flow2}.
@item X
@opindex dX
-Dump after SSA aggressive dead code elimination, to @file{@var{file}.05.ssadce}.
+Dump after SSA dead code elimination, to @file{@var{file}.06.ssadce}.
@item z
@opindex dz
-Dump after the peephole pass, to @file{@var{file}.23.peephole2}.
+Dump after the peephole pass, to @file{@var{file}.25.peephole2}.
@item a
@opindex da
Produce all the dumps listed above.
options, in particular with and without @option{-g}.
@item -fdump-translation-unit @r{(C and C++ only)}
-@itemx -fdump-translation-unit-@var{number} @r{(C and C++ only)}
+@itemx -fdump-translation-unit-@var{options} @r{(C and C++ only)}
@opindex fdump-translation-unit
Dump a representation of the tree structure for the entire translation
unit to a file. The file name is made by appending @file{.tu} to the
-source file name. If the @samp{-@var{number}} form is used, @var{number}
-controls the details of the dump as described for the @option{-fdump-tree} options.
+source file name. If the @samp{-@var{options}} form is used, @var{options}
+controls the details of the dump as described for the
+@option{-fdump-tree} options.
@item -fdump-class-hierarchy @r{(C++ only)}
-@itemx -fdump-class-hierarchy-@var{number} @r{(C++ only)}
+@itemx -fdump-class-hierarchy-@var{options} @r{(C++ only)}
@opindex fdump-class-hierarchy
Dump a representation of each class's hierarchy and virtual function
table layout to a file. The file name is made by appending @file{.class}
-to the source file name. If the @samp{-@var{number}} form is used, @var{number}
-controls the details of the dump as described for the @option{-fdump-tree}
-options.
-
-@item -fdump-ast-@var{switch} @r{(C++ only)}
-@itemx -fdump-ast-@var{switch}-@var{number} @r{(C++ only)}
-@opindex fdump-ast
-Control the dumping at various stages of processing the abstract syntax
-tree to a file. The file name is generated by appending a switch
-specific suffix to the source file name. If the @samp{-@var{number}} form is
-used, @var{number} is a bit mask which controls the details of the
-dump. The following bits are meaningful (these are not set symbolically,
-as the primary function of these dumps is for debugging gcc itself):
+to the source file name. If the @samp{-@var{options}} form is used,
+@var{options} controls the details of the dump as described for the
+@option{-fdump-tree} options.
+
+@item -fdump-tree-@var{switch} @r{(C++ only)}
+@itemx -fdump-tree-@var{switch}-@var{options} @r{(C++ only)}
+@opindex fdump-tree
+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. If the @samp{-@var{options}}
+form is used, @var{options} is a list of @samp{-} separated options that
+control the details of the dump. Not all options are applicable to all
+dumps, those which are not meaningful will be ignored. The following
+options are available
@table @samp
-@item bit0 (1)
+@item address
Print the address of each node. Usually this is not meaningful as it
-changes according to the environment and source file.
-@item bit1 (2)
-Inhibit dumping of members of a scope or body of a function, unless they
-are reachable by some other path.
+changes according to the environment and source file. Its primary use
+is for tying up a dump file with a debug environment.
+@item slim
+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.
+@item all
+Turn on all options.
@end table
The following tree dumps are possible:
@item optimized
Dump after all tree based optimization, to @file{@var{file}.optimized}.
@item inlined
-Dump after inlining within the body of the function, to
-@file{@var{file}.inlined}.
+Dump after function inlining, to @file{@var{file}.inlined}.
@end table
@item -fpretend-float
change the program counter to any other statement in the function and
get exactly the results you would expect from the source code.
-Without @option{-O}, the compiler only allocates variables declared
-@code{register} in registers. The resulting compiled code is a little
-worse than produced by PCC without @option{-O}.
-
With @option{-O}, the compiler tries to reduce code size and execution
-time.
-
-When you specify @option{-O}, the compiler turns on @option{-fthread-jumps}
-and @option{-fdefer-pop} on all machines. The compiler turns on
-@option{-fdelayed-branch} on machines that have delay slots, and
-@option{-fomit-frame-pointer} on machines that can support debugging even
-without a frame pointer. On some machines the compiler also turns
-on other flags.
+time, without performing any optimizations that take a great deal of
+compilation time.
@item -O2
@opindex O2
@option{-fforce-mem} option on all machines and frame pointer elimination
on machines where doing so does not interfere with debugging.
+Please note the warning under @option{-fgcse} about
+invoking @option{-O2} on programs that use computed gotos.
+
@item -O3
@opindex O3
Optimize yet more. @option{-O3} turns on all optimizations specified by
in many functions. @strong{It also makes debugging impossible on
some machines.}
-@ifset INTERNALS
-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 @code{FRAME_POINTER_REQUIRED} controls
-whether a target machine supports this flag. @xref{Registers}.
-@end ifset
-@ifclear INTERNALS
-On some machines, such as the Vax, this flag has no effect, because
+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 @code{FRAME_POINTER_REQUIRED} controls
whether a target machine supports this flag. @xref{Registers,,Register
-Usage, gcc.info, Using and Porting GCC}.
-@end ifclear
+Usage, gccint, GNU Compiler Collection (GCC) Internals}.
@item -foptimize-sibling-calls
@opindex foptimize-sibling-calls
inline (ie marked with the inline keyword or defined within the class
definition in c++). @var{n} is the size of functions that can be inlined in
number of pseudo instructions (not counting parameter handling). The default
-value of @var{n} is 10000. Increasing this value can result in more inlined code at
+value of @var{n} is 600.
+Increasing this value can result in more inlined code at
the cost of compilation time and memory consumption. Decreasing usually makes
the compilation faster and less code will be inlined (which presumably
means slower programs). This option is particularly useful for programs that
check if the variable was referenced, regardless of whether or not
optimization is turned on, use the @option{-fno-keep-static-consts} option.
+@item -fmerge-constants
+Attempt to merge identical constants (string constants and floating point
+constants) accross compilation units.
+
+This option is default for optimized compilation if assembler and linker
+support it. Use @option{-fno-merge-constants} to inhibit this behavior.
+
+@item -fmerge-all-constants
+Attempt to merge identical constants and identical variables.
+
+This option implies @option{-fmerge-constants}. In addition to
+@option{-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 non-automatic variable to
+have distinct location, so using this option will result in non-conforming
+behavior.
+
@item -fno-function-cse
@opindex fno-function-cse
Do not put function addresses in registers; make each instruction that
@item -ffast-math
@opindex ffast-math
-Sets @option{-fno-math-errno}, @option{-funsafe-math-optimizations},
-and @option{-fno-trapping-math}.
+Sets @option{-fno-math-errno}, @option{-funsafe-math-optimizations}, and @*
+@option{-fno-trapping-math}.
This option causes the preprocessor macro @code{__FAST_MATH__} to be defined.
an exact implementation of IEEE or ISO rules/specifications for
math functions.
-The default is @option{-fmath-errno}. The @option{-ffast-math} option
-sets @option{-fno-math-errno}.
+The default is @option{-fmath-errno}.
@item -funsafe-math-optimizations
@opindex funsafe-math-optimizations
an exact implementation of IEEE or ISO rules/specifications for
math functions.
-The default is @option{-fno-unsafe-math-optimizations}. The
-@option{-ffast-math} option sets @option{-funsafe-math-optimizations}.
+The default is @option{-fno-unsafe-math-optimizations}.
@item -fno-trapping-math
@opindex fno-trapping-math
an exact implementation of IEEE or ISO rules/specifications for
math functions.
-The default is @option{-ftrapping-math}. The @option{-ffast-math}
-option sets @option{-fno-trapping-math}.
+The default is @option{-ftrapping-math}.
+
+@item -fno-zero-initialized-in-bss
+@opindex 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 @option{-fzero-initialized-in-bss}.
@end table
-@c following causes underfulls.. they don't look great, but we deal.
-@c --mew 26jan93
The following options control specific optimizations. The @option{-O2}
option turns on all of these optimizations except @option{-funroll-loops}
and @option{-funroll-all-loops}. On most machines, the @option{-O} option
You can use the following flags in the rare cases when ``fine-tuning''
of optimizations to be performed is desired.
+Not all of the optimizations performed by GCC have @option{-f} options
+to control them.
+
@table @gcctabopt
@item -fstrength-reduce
@opindex fstrength-reduce
Perform a global common subexpression elimination pass.
This pass also performs global constant and copy propagation.
+@emph{Note:} When compiling a program using computed gotos, a GCC
+extension, you may get better runtime performance if you disable
+the global common subexpression elmination pass by adding
+@option{-fno-gcse} to the command line.
+
@item -fgcse-lm
@opindex fgcse-lm
When @option{-fgcse-lm} is enabled, global common subexpression elimination will
@item -fdelete-null-pointer-checks
@opindex fdelete-null-pointer-checks
-Use global dataflow analysis to identify and eliminate useless null
-pointer checks. Programs which rely on NULL pointer dereferences @emph{not}
-halting the program may not work properly with this option. Use
-@option{-fno-delete-null-pointer-checks} to disable this optimizing for programs
-which depend on that behavior.
+Use global dataflow analysis to identify and eliminate useless checks
+for null pointers. The compiler assumes that dereferencing a null
+pointer would have halted the program. If a pointer is checked after
+it has already been dereferenced, it cannot be null.
+
+In some environments, this assumption is not true, and programs can
+safely dereference null pointers. Use
+@option{-fno-delete-null-pointer-checks} to disable this optimization
+for programs which depend on that behavior.
@item -fexpensive-optimizations
@opindex fexpensive-optimizations
@item -funroll-loops
@opindex funroll-loops
-Perform the optimization of loop unrolling. This is only done for loops
-whose number of iterations can be determined at compile time or run time.
-@option{-funroll-loops} implies both @option{-fstrength-reduce} and
-@option{-frerun-cse-after-loop}.
+Unroll loops whose number of iterations can be determined at compile
+time or upon entry to the loop. @option{-funroll-loops} implies both
+@option{-fstrength-reduce} and @option{-frerun-cse-after-loop}. This
+option makes code larger, and may or may not make it run faster.
@item -funroll-all-loops
@opindex funroll-all-loops
-Perform the optimization of loop unrolling. This is done for all loops
-and usually makes programs run more slowly. @option{-funroll-all-loops}
-implies @option{-fstrength-reduce} as well as @option{-frerun-cse-after-loop}.
+Unroll all loops, even if their number of iterations is uncertain when
+the loop is entered. This usually makes programs run more slowly.
+@option{-funroll-all-loops} implies the same options as
+@option{-funroll-loops},
+
+@item -fprefetch-loop-arrays
+@opindex fprefetch-loop-arrays
+If supported by the target machine, generate instructions to prefetch
+memory to improve the performance of loops that access large arrays.
@item -fmove-all-movables
@opindex fmove-all-movables
(@pxref{Debugging Options,, Options for Debugging Your Program or
@command{gcc}}), you can compile it a second time using
@option{-fbranch-probabilities}, to improve optimizations based on
-guessing the path a branch might take.
+the number of times each branch was taken. When the program
+compiled with @option{-fprofile-arcs} exits it saves arc execution
+counts to a file called @file{@var{sourcename}.da} 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.
-@ifset INTERNALS
With @option{-fbranch-probabilities}, GCC puts a @samp{REG_EXEC_COUNT}
note on the first instruction of each basic block, and a
@samp{REG_BR_PROB} note on each @samp{JUMP_INSN} and @samp{CALL_INSN}.
used in one place: in @file{reorg.c}, instead of guessing which path a
branch is mostly to take, the @samp{REG_BR_PROB} values are used to
exactly determine which path is taken more often.
-@end ifset
@item -fno-guess-branch-probability
@opindex fno-guess-branch-probability
-Sometimes gcc will opt to guess branch probabilities when none are
-available from either profile directed feedback (@option{-fprofile-arcs})
-or @samp{__builtin_expect}. In a hard real-time system, people don't
-want different runs of the compiler to produce code that has different
-behavior; minimizing non-determinism is of paramount import. This
-switch allows users to reduce non-determinism, possibly at the expense
-of inferior optimization.
+Do not guess branch probabilities using a randomized model.
+
+Sometimes gcc will opt to use a randomized model to guess branch
+probabilities, when none are available from either profiling feedback
+(@option{-fprofile-arcs}) or @samp{__builtin_expect}. This means that
+different runs of the compiler on the same program may produce different
+object code.
+
+In a hard real-time system, people don't want different runs of the
+compiler to produce code that has different behavior; minimizing
+non-determinism is of paramount import. This switch allows users to
+reduce non-determinism, possibly at the expense of inferior
+optimization.
@item -fstrict-aliasing
@opindex fstrict-aliasing
@}
@end example
-@ifset INTERNALS
Every language that wishes to perform language-specific alias analysis
should define a function that computes, given an @code{tree}
node, an alias set for the node. Nodes in different alias sets are not
allowed to alias. For an example, see the C front-end function
@code{c_get_alias_set}.
-@end ifset
@item -falign-functions
@itemx -falign-functions=@var{n}
the flow graph is translated back from SSA form. Users should not
specify this option, since it is not yet ready for production use.
+@item -fssa-ccp
+@opindex fssa-ccp
+Perform Sparse Conditional Constant Propagation in SSA form. Requires
+@option{-fssa}. Like @option{-fssa}, this is an experimental feature.
+
@item -fssa-dce
@opindex fssa-dce
Perform aggressive dead-code elimination in SSA form. Requires @option{-fssa}.
make debugging impossible, since variables will no longer stay in
a ``home register''.
+@item -fno-cprop-registers
+@opindex fno-cprop-registers
+After register allocation and post-register allocation instruction splitting,
+we perform a copy-propagation pass to try to reduce scheduling dependencies
+and occasionally eliminate the copy.
+
@item --param @var{name}=@var{value}
@opindex param
In some places, GCC uses various constants to control the amount of
control some of these constants on the command-line using the
@option{--param} option.
-In each case, the @var{value} is a integer. The allowable choices for
+In each case, the @var{value} is an integer. The allowable choices for
@var{name} are given in the following table:
@table @gcctabopt
optimization will not be done.
@item max-gcse-passes
-The maximum number of passes of GCSE to run.
+The maximum number of passes of GCSE to run.
+
+@item max-pending-list-length
+The maximum number of pending dependencies scheduling will allow
+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.
@item max-inline-insns
If an function contains more than this many instructions, it
@item -M
@opindex M
Instead of outputting the result of preprocessing, output a rule
-suitable for @code{make} describing the dependencies of the main source
-file. The preprocessor outputs one @code{make} rule containing the
-object file name for that source file, a colon, and the names of all the
-included files. Unless overridden explicitly, the object file name
-consists of the basename of the source file with any suffix replaced with
-object file suffix. If there are many included files then the
-rule is split into several lines using @samp{\}-newline.
+suitable for @command{make} describing the dependencies of the main
+source file. The preprocessor outputs one @command{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 @option{-include} or
+@option{-imacros} command line options.
+
+Unless specified explicitly (with @option{-MT} or @option{-MQ}), the
+object file name consists of the basename of the source file with any
+suffix replaced with object file suffix. If there are many included
+files then the rule is split into several lines using @samp{\}-newline.
+The rule has no commands.
-@option{-M} implies @option{-E}.
+Passing @option{-M} to the driver implies @option{-E}.
@item -MM
@opindex MM
-Like @option{-M}, but mention only the files included with @samp{#include
-"@var{file}"}. System header files included with @samp{#include
-<@var{file}>} are omitted.
+Like @option{-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
+@samp{#include} directive does not in itself determine whether that
+header will appear in @option{-MM} dependency output. This is a
+slight change in semantics from GCC versions 3.0 and earlier.
@item -MD
@opindex MD
-Like @option{-M} but the dependency information is written to a file
-rather than stdout. @code{gcc} will use the same file name and
-directory as the object file, but with the suffix @file{.d} instead.
+@option{-MD} is equivalent to @option{-M -MF @var{file}}, except that
+@option{-E} is not implied. The driver determines @var{file} based on
+whether an @option{-o} option is given. If it is, the driver uses its
+argument but with a suffix of @file{.d}, otherwise it take the
+basename of the input file and applies a @file{.d} suffix.
+
+If @option{-MD} is used in conjunction with @option{-E}, any
+@option{-o} switch is understood to specify the dependency output file
+(but @pxref{-MF}), but if used without @option{-E}, each @option{-o}
+is understood to specify a target object file.
-This is in addition to compiling the main file as specified---@option{-MD}
-does not inhibit ordinary compilation the way @option{-M} does,
-unless you also specify @option{-MG}.
+Since @option{-E} is not implied, @option{-MD} can be used to generate
+a dependency output file as a side-effect of the compilation process.
With Mach, you can use the utility @code{md} to merge multiple
dependency files into a single dependency file suitable for using with
@item -MF @var{file}
@opindex MF
-When used with @option{-M} or @option{-MM}, specifies a file to write the
-dependencies to. This allows the preprocessor to write the preprocessed
-file to stdout normally. If no @option{-MF} switch is given, CPP sends
-the rules to stdout and suppresses normal preprocessed output.
+@anchor{-MF}
+When used with @option{-M} or @option{-MM}, specifies a
+file to write the dependencies to. If no @option{-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 @option{-MD} or @option{-MMD},
+@option{-MF} overrides the default dependency output file.
Another way to specify output of a @code{make} rule is by setting
the environment variable @env{DEPENDENCIES_OUTPUT} (@pxref{Environment
@option{-nodefaultlibs} is @file{libgcc.a}, a library of internal subroutines
that GCC uses to overcome shortcomings of particular machines, or special
needs for some languages.
-@ifset INTERNALS
-(@xref{Interface,,Interfacing to GCC Output}, for more discussion of
-@file{libgcc.a}.)
-@end ifset
-@ifclear INTERNALS
-(@xref{Interface,,Interfacing to GCC Output,gcc.info,Porting GCC},
+(@xref{Interface,,Interfacing to GCC Output,gccint,GNU Compiler
+Collection (GCC) Internals},
for more discussion of @file{libgcc.a}.)
-@end ifclear
In most cases, you need @file{libgcc.a} even when you want to avoid
other standard libraries. In other words, when you specify @option{-nostdlib}
or @option{-nodefaultlibs} you should usually specify @option{-lgcc} as well.
This ensures that you have no unresolved references to internal GCC
library subroutines. (For example, @samp{__main}, used to ensure C++
-constructors will be called; @pxref{Collect2,,@command{collect2}}.)
+constructors will be called; @pxref{Collect2,,@code{collect2}, gccint,
+GNU Compiler Collection (GCC) Internals}.)
@item -s
@opindex s
across different shared libraries. In that case, each of the libraries
as well as the application itself should use the shared @file{libgcc}.
-Therefore, whenever you specify the @option{-shared} option, the GCC
-driver automatically adds @option{-shared-libgcc}, unless you explicitly
-specify @option{-static-libgcc}. The G++ driver automatically adds
-@option{-shared-libgcc} when you build a main executable as well because
-for C++ programs that is typically the right thing to do.
-(Exception-handling will not work reliably otherwise.)
+Therefore, the G++ and GCJ drivers automatically add
+@option{-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 will not always be linked with the shared @file{libgcc}.
+If GCC finds, at its configuration time, that you have a GNU linker that
+does not support option @option{--eh-frame-hdr}, it will link the shared
+version of @file{libgcc} into shared libraries by default. Otherwise,
+it will take advantage of the linker and optimize away the linking with
+the shared version of @file{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, when linking a main executable written in C, you must
-explicitly say @option{-shared-libgcc} if you want to use the shared
+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
+@option{-shared-libgcc}, such that it is linked with the shared
@file{libgcc}.
@item -symbolic
one @option{-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
+@option{-isystem}, is also specified with @option{-I}, it will be
+searched only in the position requested by @option{-I}. Also, it will
+not be considered a system include directory. If that directory really
+does contain system headers, there is a good chance that they will
+break. For instance, if GCC's installation procedure edited the headers
+in @file{/usr/include} to fix bugs, @samp{-I/usr/include} will cause the
+original, buggy headers to be found instead of the corrected ones. GCC
+will issue a warning when a system include directory is hidden in this
+way.
+
@item -I-
@opindex I-
Any directories you specify with @option{-I} options before the @option{-I-}
As a special kludge, if the path provided by @option{-B} is
@file{[dir/]stage@var{N}/}, where @var{N} is a number in the range 0 to
9, then it will be replaced by @file{[dir/]include}. This is to help
-with boot-strapping the compiler.
+with boot-strapping the compiler.
@item -specs=@var{file}
@opindex specs
sequence of other programs to do the work of compiling, assembling and
linking. GCC interprets its command-line parameters and uses these to
deduce which programs it should invoke, and which command-line options
-it ought to place on their command lines. This behaviour is controlled
+it ought to place on their command lines. This behavior is controlled
by @dfn{spec strings}. In most cases there is one spec string for each
program that GCC can invoke, but a few programs have multiple spec
-strings to control their behaviour. The spec strings built into GCC can
+strings to control their behavior. The spec strings built into GCC can
be overridden by using the @option{-specs=} command-line switch to specify
a spec file.
Earlier we discussed the standard option @option{-b} which chooses among
different installed compilers for completely different target
-machines, such as Vax vs.@: 68000 vs.@: 80386.
+machines, such as VAX vs.@: 68000 vs.@: 80386.
In addition, each of these target machine types can have its own
special options, starting with @samp{-m}, to choose among various
options, usually for compatibility with other compilers on the same
platform.
-@ifset INTERNALS
These options are defined by the macro @code{TARGET_SWITCHES} in the
machine description. The default for the options is also defined by
that macro, which enables you to change the defaults.
-@end ifset
@menu
* M680x0 Options::
* RS/6000 and PowerPC Options::
* RT Options::
* MIPS Options::
-* i386 Options::
+* i386 and x86-64 Options::
* HPPA Options::
* Intel 960 Options::
* DEC Alpha Options::
+* DEC Alpha/VMS Options::
* Clipper Options::
* H8/300 Options::
* SH Options::
* MCore Options::
* IA-64 Options::
* D30V Options::
+* S/390 and zSeries Options::
+* CRIS Options::
+* MMIX Options::
+* PDP-11 Options::
+* Xstormy16 Options::
+* Xtensa Options::
@end menu
@node M680x0 Options
@subsection VAX Options
@cindex VAX options
-These @samp{-m} options are defined for the Vax:
+These @samp{-m} options are defined for the VAX:
@table @gcctabopt
@item -munix
@opindex munix
Do not output certain jump instructions (@code{aobleq} and so on)
-that the Unix assembler for the Vax cannot handle across long
+that the Unix assembler for the VAX cannot handle across long
ranges.
@item -mgnu
@itemx -msupersparc
@opindex mcypress
@opindex msupersparc
-These two options select the processor for which the code is optimised.
+These two options select the processor for which the code is optimized.
With @option{-mcypress} (the default), the compiler optimizes code for the
Cypress CY7C602 chip, as used in the SparcStation/SparcServer 3xx series.
@var{cpu_type}, but do not set the instruction set or register set that the
option @option{-mcpu=@var{cpu_type}} would.
-The same values for @option{-mcpu=@var{cpu_type}} are used for
-@option{-mtune=@var{cpu_type}}, though the only useful values are those that
-select a particular cpu implementation: @samp{cypress}, @samp{supersparc},
-@samp{hypersparc}, @samp{f930}, @samp{f934}, @samp{sparclite86x},
-@samp{tsc701}, @samp{ultrasparc}.
+The same values for @option{-mcpu=@var{cpu_type}} can be used for
+@option{-mtune=@var{cpu_type}}, but the only useful values are those
+that select a particular cpu implementation. Those are @samp{cypress},
+@samp{supersparc}, @samp{hypersparc}, @samp{f930}, @samp{f934},
+@samp{sparclite86x}, @samp{tsc701}, and @samp{ultrasparc}.
@end table
turned into long calls.
This feature is not enabled by default. Specifying
-@option{-mno-long-calls} will restore the default behaviour, as will
+@option{-mno-long-calls} will restore the default behavior, as will
placing the function calls within the scope of a @samp{#pragma
long_calls_off} directive. Note these switches have no effect on how
the compiler generates code to handle function calls via function
@opindex msingle-pic-base
Treat the register used for PIC addressing as read-only, rather than
loading it in the prologue for each function. The run-time system is
-responsible for initialising this register with an appropriate value
+responsible for initializing this register with an appropriate value
before execution begins.
@item -mpic-register=@var{reg}
These @option{-m} options are defined for Mitsubishi M32R/D architectures:
@table @gcctabopt
+@item -m32rx
+@opindex m32rx
+Generate code for the M32R/X@.
+
+@item -m32r
+@opindex m32r
+Generate code for the M32R@. This is the default.
+
@item -mcode-model=small
@opindex mcode-model=small
Assume all objects live in the lower 16MB of memory (so that their addresses
-g switch.
@item -moptimize-arg-area
-@itemx -mno-optimize-arg-area
@opindex moptimize-arg-area
-@opindex mno-optimize-arg-area
@cindex arguments in frame (88k)
-Control how function arguments are stored in stack frames.
-@option{-moptimize-arg-area} saves space by optimizing them, but this
-conflicts with the 88open specifications. The opposite alternative,
-@option{-mno-optimize-arg-area}, agrees with 88open standards. By default
-GCC does not optimize the argument area.
+Save space by reorganizing the stack frame. This option generates code
+that does not agree with the 88open specifications, but uses less
+memory.
+
+@itemx -mno-optimize-arg-area
+@opindex mno-optimize-arg-area
+Do not reorganize the stack frame to save space. This is the default.
+The generated conforms to the specification, but uses more memory.
@item -mshort-data-@var{num}
@opindex mshort-data
compiling code that might be run on such a processor, GCC
generates code that explicitly checks for zero-valued divisors
and traps with exception number 503 when one is detected. Use of
-mno-check-zero-division suppresses such checking for code
+@option{-mno-check-zero-division} suppresses such checking for code
generated to run on an MC88100 processor.
-GCC assumes that the MC88110 processor correctly detects all
-instances of integer division by zero. When @option{-m88110} is
-specified, both @option{-mcheck-zero-division} and
-@option{-mno-check-zero-division} are ignored, and no explicit checks for
-zero-valued divisors are generated.
+GCC assumes that the MC88110 processor correctly detects all instances
+of integer division by zero. When @option{-m88110} is specified, no
+explicit checks for zero-valued divisors are generated, and both
+@option{-mcheck-zero-division} and @option{-mno-check-zero-division} are
+ignored.
@item -muse-div-instruction
@opindex muse-div-instruction
GCC issues no such warning.
@end table
+@c break page here to avoid unsightly interparagraph stretch.
+@c -zw, 2001-8-17
+@page
+
@node RS/6000 and PowerPC Options
@subsection IBM RS/6000 and PowerPC Options
@cindex RS/6000 and PowerPC Options
@itemx -mold-mnemonics
@opindex mnew-mnemonics
@opindex mold-mnemonics
-Select which mnemonics to use in the generated assembler code.
-@option{-mnew-mnemonics} requests output that uses the assembler mnemonics
-defined for the PowerPC architecture, while @option{-mold-mnemonics}
-requests the assembler mnemonics defined for the POWER architecture.
-Instructions defined in only one architecture have only one mnemonic;
-GCC uses that mnemonic irrespective of which of these options is
-specified.
+Select which mnemonics to use in the generated assembler code. With
+@option{-mnew-mnemonics}, GCC uses the assembler mnemonics defined for
+the PowerPC architecture. With @option{-mold-mnemonics} it uses the
+assembler mnemonics defined for the POWER architecture. Instructions
+defined in only one architecture have only one mnemonic; GCC uses that
+mnemonic irrespective of which of these options is specified.
GCC defaults to the mnemonics appropriate for the architecture in
use. Specifying @option{-mcpu=@var{cpu_type}} sometimes overrides the
Supported values for @var{cpu_type} are @samp{rios}, @samp{rios1},
@samp{rsc}, @samp{rios2}, @samp{rs64a}, @samp{601}, @samp{602},
@samp{603}, @samp{603e}, @samp{604}, @samp{604e}, @samp{620},
-@samp{630}, @samp{740}, @samp{750}, @samp{power}, @samp{power2},
-@samp{powerpc}, @samp{403}, @samp{505}, @samp{801}, @samp{821},
-@samp{823}, and @samp{860} and @samp{common}. @option{-mcpu=power},
-@option{-mcpu=power2}, @option{-mcpu=powerpc}, and @option{-mcpu=powerpc64}
-specify generic POWER, POWER2, pure 32-bit PowerPC (i.e., not MPC601),
-and 64-bit PowerPC architecture machine types, with an appropriate,
-generic processor model assumed for scheduling purposes.
-
-Specifying any of the following options:
-@option{-mcpu=rios1}, @option{-mcpu=rios2}, @option{-mcpu=rsc},
-@option{-mcpu=power}, or @option{-mcpu=power2}
-enables the @option{-mpower} option and disables the @option{-mpowerpc} option;
-@option{-mcpu=601} enables both the @option{-mpower} and @option{-mpowerpc} options.
-All of @option{-mcpu=rs64a}, @option{-mcpu=602}, @option{-mcpu=603},
-@option{-mcpu=603e}, @option{-mcpu=604}, @option{-mcpu=620}, @option{-mcpu=630},
-@option{-mcpu=740}, and @option{-mcpu=750}
-enable the @option{-mpowerpc} option and disable the @option{-mpower} option.
-Exactly similarly, all of @option{-mcpu=403},
-@option{-mcpu=505}, @option{-mcpu=821}, @option{-mcpu=860} and @option{-mcpu=powerpc}
-enable the @option{-mpowerpc} option and disable the @option{-mpower} option.
-@option{-mcpu=common} disables both the
-@option{-mpower} and @option{-mpowerpc} options.
-
-AIX versions 4 or greater selects @option{-mcpu=common} by default, so
-that code will operate on all members of the RS/6000 POWER and PowerPC
-families. In that case, GCC will use only the instructions in the
-common subset of both architectures plus some special AIX common-mode
-calls, and will not use the MQ register. GCC assumes a generic
+@samp{630}, @samp{740}, @samp{7400}, @samp{7450}, @samp{750},
+@samp{power}, @samp{power2}, @samp{powerpc}, @samp{403}, @samp{505},
+@samp{801}, @samp{821}, @samp{823}, and @samp{860} and @samp{common}.
+
+@option{-mcpu=common} selects a completely generic processor. Code
+generated under this option will run on any POWER or PowerPC processor.
+GCC will use only the instructions in the common subset of both
+architectures, and will not use the MQ register. GCC assumes a generic
processor model for scheduling purposes.
-Specifying any of the options @option{-mcpu=rios1}, @option{-mcpu=rios2},
-@option{-mcpu=rsc}, @option{-mcpu=power}, or @option{-mcpu=power2} also
-disables the @samp{new-mnemonics} option. Specifying @option{-mcpu=601},
-@option{-mcpu=602}, @option{-mcpu=603}, @option{-mcpu=603e}, @option{-mcpu=604},
-@option{-mcpu=620}, @option{-mcpu=630}, @option{-mcpu=403}, @option{-mcpu=505},
-@option{-mcpu=821}, @option{-mcpu=860} or @option{-mcpu=powerpc} also enables
-the @samp{new-mnemonics} option.
+@option{-mcpu=power}, @option{-mcpu=power2}, @option{-mcpu=powerpc}, and
+@option{-mcpu=powerpc64} specify generic POWER, POWER2, pure 32-bit
+PowerPC (i.e., not MPC601), and 64-bit PowerPC architecture machine
+types, with an appropriate, generic processor model assumed for
+scheduling purposes.
-Specifying @option{-mcpu=403}, @option{-mcpu=821}, or @option{-mcpu=860} also
-enables the @option{-msoft-float} option.
+The other options specify a specific processor. Code generated under
+those options will run best on that processor, and may not run at all on
+others.
+
+The @option{-mcpu} options automatically enable or disable other
+@option{-m} options as follows:
+
+@table @samp
+@item common
+@option{-mno-power}, @option{-mno-powerc}
+
+@item power
+@itemx power2
+@itemx rios1
+@itemx rios2
+@itemx rsc
+@option{-mpower}, @option{-mno-powerpc}, @option{-mno-new-mnemonics}
+
+@item powerpc
+@itemx rs64a
+@itemx 602
+@itemx 603
+@itemx 603e
+@itemx 604
+@itemx 620
+@itemx 630
+@itemx 740
+@itemx 7400
+@itemx 7450
+@itemx 750
+@itemx 505
+@option{-mno-power}, @option{-mpowerpc}, @option{-mnew-mnemonics}
+
+@item 601
+@option{-mpower}, @option{-mpowerpc}, @option{-mnew-mnemonics}
+
+@item 403
+@itemx 821
+@itemx 860
+@option{-mno-power}, @option{-mpowerpc}, @option{-mnew-mnemonics}, @option{-msoft-float}
+@end table
@item -mtune=@var{cpu_type}
@opindex mtune
Set the instruction scheduling parameters for machine type
-@var{cpu_type}, but do not set the architecture type, register usage,
-choice of mnemonics like @option{-mcpu=@var{cpu_type}} would. The same
-values for @var{cpu_type} are used for @option{-mtune=@var{cpu_type}} as
-for @option{-mcpu=@var{cpu_type}}. The @option{-mtune=@var{cpu_type}}
-option overrides the @option{-mcpu=@var{cpu_type}} option in terms of
-instruction scheduling parameters.
+@var{cpu_type}, but do not set the architecture type, register usage, or
+choice of mnemonics, as @option{-mcpu=@var{cpu_type}} would. The same
+values for @var{cpu_type} are used for @option{-mtune} as for
+@option{-mcpu}. If both are specified, the code generated will use the
+architecture, registers, and mnemonics set by @option{-mcpu}, but the
+scheduling parameters set by @option{-mtune}.
+
+@item -maltivec
+@itemx -mno-altivec
+@opindex maltivec
+@opindex mno-altivec
+These switches enable or disable the use of built-in functions that
+allow access to the AltiVec instruction set. You may also need to set
+@option{-mabi=altivec} to adjust the current ABI with AltiVec ABI
+enhancements.
@item -mfull-toc
@itemx -mno-fp-in-toc
default and only is necessary when calling subroutines compiled by AIX
XL compilers without optimization.
-@item -mthreads
-@opindex mthreads
-Support @dfn{AIX Threads}. Link an application written to use
-@dfn{pthreads} with special libraries and startup code to enable the
-application to run.
-
@item -mpe
@opindex mpe
Support @dfn{IBM RS/6000 SP} @dfn{Parallel Environment} (PE)@. Link an
standard location (@file{/usr/lpp/ppe.poe/}), or the @file{specs} file
must be overridden with the @option{-specs=} option to specify the
appropriate directory location. The Parallel Environment does not
-support threads, so the @option{-mpe} option and the @option{-mthreads}
+support threads, so the @option{-mpe} option and the @option{-pthread}
option are incompatible.
@item -msoft-float
On System V.4 and embedded PowerPC systems compile code for the
Linux-based GNU system.
+@item -mcall-gnu
+@opindex mcall-gnu
+On System V.4 and embedded PowerPC systems compile code for the
+Hurd-based GNU system.
+
+@item -mcall-netbsd
+@opindex mcall-netbsd
+On System V.4 and embedded PowerPC systems compile code for the
+NetBSD operating system.
+
+@item -maix-struct-return
+@opindex maix-struct-return
+Return all structures in memory (as specified by the AIX ABI)@.
+
+@item -msvr4-struct-return
+@opindex msvr4-struct-return
+Return structures smaller than 8 bytes in registers (as specified by the
+SVR4 ABI)@.
+
+@item -mabi=altivec
+@opindex mabi=altivec
+Extend the current ABI with AltiVec ABI extensions. This does not
+change the default ABI, instead it adds the AltiVec ABI extensions to
+the current ABI@.
+
@item -mprototype
@itemx -mno-prototype
@opindex mprototype
On System V.4 and embedded PowerPC systems do (do not) emit register
names in the assembly language output using symbolic forms.
+@item -pthread
+@opindex pthread
+Adds support for multithreading with the @dfn{pthreads} library.
+This option sets flags for both the preprocessor and linker.
+
@end table
@node RT Options
These @samp{-m} options are defined for the MIPS family of computers:
@table @gcctabopt
-@item -mcpu=@var{cpu-type}
-@opindex mcpu
+
+@item -march=@var{cpu-type}
+@opindex march
+Assume the defaults for the machine type @var{cpu-type} when generating
+instructions. The choices for @var{cpu-type} are @samp{r2000}, @samp{r3000},
+@samp{r3900}, @samp{r4000}, @samp{r4100}, @samp{r4300}, @samp{r4400},
+@samp{r4600}, @samp{r4650}, @samp{r5000}, @samp{r6000}, @samp{r8000},
+and @samp{orion}. Additionally, the @samp{r2000}, @samp{r3000},
+@samp{r4000}, @samp{r5000}, and @samp{r6000} can be abbreviated as
+@samp{r2k} (or @samp{r2K}), @samp{r3k}, etc.
+
+@item -mtune=@var{cpu-type}
+@opindex mtune
Assume the defaults for the machine type @var{cpu-type} when scheduling
instructions. The choices for @var{cpu-type} are @samp{r2000}, @samp{r3000},
@samp{r3900}, @samp{r4000}, @samp{r4100}, @samp{r4300}, @samp{r4400},
of the MIPS ISA (instruction set architecture) without a @option{-mipsX}
or @option{-mabi} switch being used.
+@item -mcpu=@var{cpu-type}
+@opindex mcpu
+This is identical to specifying both @option{-march} and @option{-mtune}.
+
@item -mips1
@opindex mips1
Issue instructions from level 1 of the MIPS ISA@. This is the default.
Assume that 32 64-bit floating point registers are available. This is
the default when the @option{-mips3} option is used.
+@item -mfused-madd
+@itemx -mno-fused-madd
+@opindex mfused-madd
+@opindex mno-fused-madd
+Generate code that uses (does not use) the floating point multiply and
+accumulate instructions, when they are available. These instructions
+are generated by default if they are available, but this may be
+undesirable if the extra precision causes problems or on certain chips
+in the mode where denormals are rounded to zero where denormals
+generated by multiply and accumulate instructions cause exceptions
+anyway.
+
@item -mgp32
@opindex mgp32
Assume that 32 32-bit general purpose registers are available. This is
@item -no-crt0
@opindex no-crt0
Do not include the default crt0.
+
+@item -mflush-func=@var{func}
+@itemx -mno-flush-func
+@opindex mflush-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 @code{_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
+@samp{_flush_func} or @samp{__cpu_flush}.
@end table
-@ifset INTERNALS
These options are defined by the macro
@code{TARGET_SWITCHES} in the machine description. The default for the
options is also defined by that macro, which enables you to change the
defaults.
-@end ifset
-@node i386 Options
-@subsection Intel 386 Options
+@node i386 and x86-64 Options
+@subsection Intel 386 and AMD x86-64 Options
@cindex i386 Options
+@cindex x86-64 Options
@cindex Intel 386 Options
+@cindex AMD x86-64 Options
-These @samp{-m} options are defined for the i386 family of computers:
+These @samp{-m} options are defined for the i386 and x86-64 family of
+computers:
@table @gcctabopt
@item -mcpu=@var{cpu-type}
@opindex mcpu
-Assume the defaults for the machine type @var{cpu-type} when scheduling
-instructions. The choices for @var{cpu-type} are @samp{i386},
-@samp{i486}, @samp{i586}, @samp{i686}, @samp{pentium},
-@samp{pentiumpro}, @samp{pentium4}, @samp{k6}, and @samp{athlon}
+Tune to @var{cpu-type} everything applicable about the generated code, except
+for the ABI and the set of available instructions. The choices for
+@var{cpu-type} are @samp{i386}, @samp{i486}, @samp{i586}, @samp{i686},
+@samp{pentium}, @samp{pentium-mmx}, @samp{pentiumpro}, @samp{pentium2},
+@samp{pentium3}, @samp{pentium4}, @samp{k6}, @samp{k6-2}, @samp{k6-3},
+@samp{athlon}, @samp{athlon-tbird}, @samp{athlon-4}, @samp{athlon-xp}
+and @samp{athlon-mp}.
While picking a specific @var{cpu-type} will schedule things appropriately
for that particular chip, the compiler will not generate any code that
@opindex m486
@opindex mpentium
@opindex mpentiumpro
-Synonyms for @option{-mcpu=i386}, @option{-mcpu=i486}, @option{-mcpu=pentium}, and @option{-mcpu=pentiumpro}
-respectively. These synonyms are deprecated.
+These options are synonyms for @option{-mcpu=i386}, @option{-mcpu=i486},
+@option{-mcpu=pentium}, and @option{-mcpu=pentiumpro} respectively.
+These synonyms are deprecated.
-@item -mintel-syntax
-@opindex mintel-syntax
-Emit assembly using Intel syntax opcodes instead of AT&T syntax.
+@item -mfpmath=@var{unit}
+@opindex march
+generate floating point arithmetics for selected unit @var{unit}. the choices
+for @var{unit} are:
+
+@table @samp
+@item 387
+Use the standard 387 floating point coprocessor present majority of chips and
+emulated otherwise. Code compiled with this option will run almost everywhere.
+The temporary results are computed in 80bit precesion instead of precision
+specified by the type resulting in slightly different results compared to most
+of other chips. See @option{-ffloat-store} for more detailed description.
+
+This is the default choice for i386 compiler.
+
+@item sse
+Use scalar floating point instructions present in the SSE instruction set.
+This instruction set is supported by Pentium3 and newer chips, in the AMD line
+by Athlon-4, Athlon-xp and Athlon-mp chips. The earlier version of SSE
+instruction set supports only single precision arithmetics, thus the double and
+extended precision arithmetics is still done using 387. Later version, present
+only in Pentium4 and the future AMD x86-64 chips supports double precision
+arithmetics too.
+
+For i387 you need to use @option{-march=@var{cpu-type}}, @option{-msse} or
+@option{-msse2} switches to enable SSE extensions and make this option
+effective. For x86-64 compiler, these extensions are enabled by default.
+
+The resulting code should be considerably faster in majority of cases and avoid
+the numerical instability problems of 387 code, but may break some existing
+code that expects temporaries to be 80bit.
+
+This is the default choice for x86-64 compiler.
+
+@item sse,387
+Attempt to utilize both instruction sets at once. This effectivly double 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 gcc register allocator does not model separate
+functional units well resulting in instable performance.
+@end table
+
+@item -masm=@var{dialect}
+@opindex masm=@var{dialect}
+Output asm instructions using selected @var{dialect}. Supported choices are
+@samp{intel} or @samp{att} (the default one).
@item -mieee-fp
@itemx -mno-ieee-fp
expense of more memory.
@item -m128bit-long-double
-@itemx -m128bit-long-double
-@opindex m128bit-long-double
@opindex m128bit-long-double
Control the size of @code{long double} type. i386 application binary interface
specify the size to be 12 bytes, while modern architectures (Pentium and newer)
will be modified.
@item -m96bit-long-double
-@itemx -m96bit-long-double
-@opindex m96bit-long-double
@opindex m96bit-long-double
Set the size of @code{long double} to 96 bits as required by the i386
application binary interface. This is the default.
@itemx -mno-svr3-shlib
@opindex msvr3-shlib
@opindex mno-svr3-shlib
-Control whether GCC places uninitialized locals into @code{bss} or
-@code{data}. @option{-msvr3-shlib} places these locals into @code{bss}.
-These options are meaningful only on System V Release 3.
-
-@item -mno-wide-multiply
-@itemx -mwide-multiply
-@opindex mno-wide-multiply
-@opindex mwide-multiply
-Control whether GCC uses the @code{mul} and @code{imul} that produce
-64-bit results in @code{eax:edx} from 32-bit operands to do @code{long
-long} multiplies and 32-bit division by constants.
+Control whether GCC places uninitialized local variables into the
+@code{bss} or @code{data} segments. @option{-msvr3-shlib} places them
+into @code{bss}. These options are meaningful only on System V Release 3.
@item -mrtd
@opindex mrtd
@opindex mpreferred-stack-boundary
Attempt to keep the stack boundary aligned to a 2 raised to @var{num}
byte boundary. If @option{-mpreferred-stack-boundary} is not specified,
-the default is 4 (16 bytes or 128 bits).
+the default is 4 (16 bytes or 128 bits), except when optimizing for code
+size (@option{-Os}), in which case the default is the minimum correct
+alignment (4 bytes for x86, and 8 bytes for x86-64).
-The stack is required to be aligned on a 4 byte boundary. On Pentium
-and PentiumPro, @code{double} and @code{long double} values should be
-aligned to an 8 byte boundary (see @option{-malign-double}) or suffer
-significant run time performance penalties. On Pentium III, the
+On Pentium and PentiumPro, @code{double} and @code{long double} values
+should be aligned to an 8 byte boundary (see @option{-malign-double}) or
+suffer significant run time performance penalties. On Pentium III, the
Streaming SIMD Extension (SSE) data type @code{__m128} suffers similar
penalties if it is not 16 byte aligned.
boundary will most likely misalign the stack. It is recommended that
libraries that use callbacks always use the default setting.
-This extra alignment does consume extra stack space. Code that is sensitive
-to stack space usage, such as embedded systems and operating system kernels,
-may want to reduce the preferred alignment to
-@option{-mpreferred-stack-boundary=2}.
+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 @option{-mpreferred-stack-boundary=2}.
+
+@item -mmmx
+@itemx -mno-mmx
+@item -msse
+@itemx -mno-sse
+@item -msse2
+@itemx -mno-sse2
+@item -m3dnow
+@itemx -mno-3dnow
+@opindex mmmx
+@opindex mno-mmx
+@opindex msse
+@opindex mno-sse
+@opindex m3dnow
+@opindex mno-3dnow
+These switches enable or disable the use of built-in functions that allow
+direct access to the MMX, SSE and 3Dnow extensions of the instruction set.
+
+@xref{X86 Built-in Functions}, for details of the functions enabled
+and disabled by these switches.
@item -mpush-args
+@itemx -mno-push-args
@opindex mpush-args
+@opindex 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
@item -maccumulate-outgoing-args
@opindex maccumulate-outgoing-args
If enabled, the maximum amount of space required for outgoing arguments will be
-computed in the function prologue. This in faster on most modern CPUs
+computed in the function prologue. This is faster on most modern CPUs
because of reduced dependencies, improved scheduling and reduced stack usage
when preferred stack boundary is not equal to 2. The drawback is a notable
increase in code size. This switch implies @option{-mno-push-args}.
which might make debugging harder.
@end table
+These @samp{-m} switches are supported in addition to the above
+on AMD x86-64 processors in 64-bit environments.
+
+@table @gcctabopt
+@item -m32
+@itemx -m64
+@opindex m32
+@opindex m64
+Generate code for a 32-bit or 64-bit environment.
+The 32-bit environment sets int, long and pointer to 32 bits and
+generates code that runs on any i386 system.
+The 64-bit environment sets int to 32 bits and long and pointer
+to 64 bits and generates code for AMD's x86-64 architecture.
+
+@item -mno-red-zone
+@opindex no-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 will not be modified by signal or interrupt handlers
+and therefore can be used for temporary data without adjusting the stack
+pointer. The flag @option{-mno-red-zone} disables this red zone.
+@end table
+
@node HPPA Options
@subsection HPPA Options
@cindex HPPA Options
@option{-mno-fp-regs} implies @option{-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
+in @code{$0} instead of @code{$f0}. This is a non-standard calling sequence,
+so any function with a floating-point argument or return value called by code
compiled with @option{-mno-fp-regs} must also be compiled with that
option.
point standard. However, for full compliance, software assistance is
required. This option generates code fully IEEE compliant code
@emph{except} that the @var{inexact-flag} is not maintained (see below).
-If this option is turned on, the CPP macro @code{_IEEE_FP} is defined
-during compilation. The option is a shorthand for: @option{-D_IEEE_FP
--mfp-trap-mode=su -mtrap-precision=i -mieee-conformant}. 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
-@option{-ieee_with_no_inexact}.
+If this option is turned on, the preprocessor macro @code{_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 @option{-ieee_with_no_inexact}.
@item -mieee-with-inexact
@opindex mieee-with-inexact
-@c overfull hbox here --bob 22 jul96
-@c original text between ignore ... end ignore
-@ignore
-This is like @option{-mieee} except the generated code also maintains the
-IEEE @var{inexact-flag}. Turning on this option causes the generated
-code to implement fully-compliant IEEE math. The option is a shorthand
-for @option{-D_IEEE_FP -D_IEEE_FP_INEXACT} plus @option{-mieee-conformant},
-@option{-mfp-trap-mode=sui}, and @option{-mtrap-precision=i}. 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 @var{inexact-flag}, you should normally not specify this
-option. Other Alpha compilers call this option
-@option{-ieee_with_inexact}.
-@end ignore
-@c changed paragraph
-This is like @option{-mieee} except the generated code also maintains the
-IEEE @var{inexact-flag}. Turning on this option causes the generated
-code to implement fully-compliant IEEE math. The option is a shorthand
-for @option{-D_IEEE_FP -D_IEEE_FP_INEXACT} plus the three following:
-@option{-mieee-conformant},
-@option{-mfp-trap-mode=sui},
-and @option{-mtrap-precision=i}.
-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 @var{inexact-flag}, you should
+This is like @option{-mieee} except the generated code also maintains
+the IEEE @var{inexact-flag}. Turning on this option causes the
+generated code to implement fully-compliant IEEE math. In addition to
+@code{_IEEE_FP}, @code{_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 @var{inexact-flag}, you should
normally not specify this option. Other Alpha compilers call this
option @option{-ieee_with_inexact}.
-@c end changes to prevent overfull hboxes
@item -mfp-trap-mode=@var{trap-mode}
@opindex mfp-trap-mode
@itemx -mno-bwx
@itemx -mcix
@itemx -mno-cix
+@itemx -mfix
+@itemx -mno-fix
@itemx -mmax
@itemx -mno-max
@opindex mbwx
@opindex mno-bwx
@opindex mcix
@opindex mno-cix
+@opindex mfix
+@opindex mno-fix
@opindex mmax
@opindex mno-max
Indicate whether GCC should generate code to use the optional BWX,
-CIX, and MAX instruction sets. The default is to use the instruction sets
-supported by the CPU type specified via @option{-mcpu=} option or that
+CIX, FIX and MAX instruction sets. The default is to use the instruction
+sets supported by the CPU type specified via @option{-mcpu=} option or that
of the CPU on which GCC was built if none was specified.
+@item -mfloat-vax
+@itemx -mfloat-ieee
+@opindex mfloat-vax
+@opindex mfloat-ieee
+Generate code that uses (does not use) VAX F and G floating point
+arithmetic instead of IEEE single and double precision.
+
+@item -mexplicit-relocs
+@itemx -mno-explicit-relocs
+@opindex mexplicit-relocs
+@opindex mno-explicit-relocs
+Older Alpha assemblers provided no way to generate symbol relocations
+except via assembler macros. Use of these macros does not allow
+optimial 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.
+
+@item -msmall-data
+@itemx -mlarge-data
+@opindex msmall-data
+@opindex mlarge-data
+When @option{-mexplicit-relocs} is in effect, static data is
+accessed via @dfn{gp-relative} relocations. When @option{-msmall-data}
+is used, objects 8 bytes long or smaller are placed in a @dfn{small data area}
+(the @code{.sdata} and @code{.sbss} sections) and are accessed via
+16-bit relocations off of the @code{$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 @option{-mlarge-data}. With this option the data area
+is limited to just below 2GB. Programs that require more than 2GB of
+data must use @code{malloc} or @code{mmap} to allocate the data in the
+heap instead of in the program's data segment.
+
+When generating code for shared libraries, @option{-fpic} implies
+@option{-msmall-data} and @option{-fPIC} implies @option{-mlarge-data}.
+
@item -mcpu=@var{cpu_type}
@opindex mcpu
-Set the instruction set, register set, and instruction scheduling
-parameters for machine type @var{cpu_type}. You can specify either the
-@samp{EV} style name or the corresponding chip number. GCC
-supports scheduling parameters for the EV4 and EV5 family of processors
-and will choose the default values for the instruction set from
-the processor you specify. If you do not specify a processor type,
-GCC will default to the processor on which the compiler was built.
+Set the instruction set and instruction scheduling parameters for
+machine type @var{cpu_type}. You can specify either the @samp{EV}
+style name or the corresponding chip number. GCC supports scheduling
+parameters for the EV4, EV5 and EV6 family of processors and will
+choose the default values for the instruction set from the processor
+you specify. If you do not specify a processor type, GCC will default
+to the processor on which the compiler was built.
Supported values for @var{cpu_type} are
@table @samp
@item ev4
+@item ev45
@itemx 21064
Schedules as an EV4 and has no instruction set extensions.
@item ev6
@itemx 21264
-Schedules as an EV5 (until Digital releases the scheduling parameters
-for the EV6) and supports the BWX, CIX, and MAX extensions.
+Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.
+
+@item ev67
+@item 21264a
+Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.
@end table
+@item -mtune=@var{cpu_type}
+@opindex mtune
+Set only the instruction scheduling parameters for machine type
+@var{cpu_type}. The instruction set is not changed.
+
@item -mmemory-latency=@var{time}
@opindex mmemory-latency
Sets the latency the scheduler should assume for typical memory
@end table
@end table
+@node DEC Alpha/VMS Options
+@subsection DEC Alpha/VMS Options
+
+These @samp{-m} options are defined for the DEC Alpha/VMS implementations:
+
+@table @gcctabopt
+@item -mvms-return-codes
+@opindex mvms-return-codes
+Return VMS condition codes from main. The default is to return POSIX
+style condition (e.g.@ error) codes.
+@end table
+
@node Clipper Options
@subsection Clipper Options
@item -mc400
@opindex mc400
-Produce code for a C400 Clipper processor i.e.@: use floating point
-registers f8---f15.
+Produce code for a C400 Clipper processor, i.e.@: use floating point
+registers f8--f15.
@end table
@node H8/300 Options
@opindex mmulti-add
Try and generate multiply-add floating point instructions @code{polyF}
and @code{dotF}. This option is only available if the @option{-m32381}
-option is in effect. Using these instructions requires changes to to
+option is in effect. Using these instructions requires changes to
register allocation which generally has a negative impact on
performance. This option should only be enabled when compiling code
particularly likely to make heavy use of multiply-add instructions.
at90c8534, at90s8535).
Instruction set avr3 is for the classic AVR core with up to 128K program
-memory space (MCU types: atmega103, atmega603).
+memory space (MCU types: atmega103, atmega603, at43usb320, at76c711).
Instruction set avr4 is for the enhanced AVR core with up to 8K program
-memory space (MCU types: atmega83, atmega85).
+memory space (MCU types: atmega8, atmega83, atmega85).
Instruction set avr5 is for the enhanced AVR core with up to 128K program
-memory space (MCU types: atmega161, atmega163, atmega32, at94k).
+memory space (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323,
+atmega64, atmega128, at43usb355, at94k).
@item -msize
@opindex msize
replace a branch. The default is 4.
@end table
+@node S/390 and zSeries Options
+@subsection S/390 and zSeries Options
+@cindex S/390 and zSeries Options
+
+These are the @samp{-m} options defined for the S/390 and zSeries architecture.
+
+@table @gcctabopt
+@item -mhard-float
+@itemx -msoft-float
+@opindex mhard-float
+@opindex msoft-float
+Use (do not use) the hardware floating-point instructions and registers
+for floating-point operations. When @option{-msoft-float} is specified,
+functions in @file{libgcc.a} will be used to perform floating-point
+operations. When @option{-mhard-float} is specified, the compiler
+generates IEEE floating-point instructions. This is the default.
+
+@item -mbackchain
+@itemx -mno-backchain
+@opindex mbackchain
+@opindex mno-backchain
+Generate (or do not generate) code which maintains an explicit
+backchain within the stack frame that points to the caller's frame.
+This is currently needed to allow debugging. The default is to
+generate the backchain.
+
+@item -msmall-exec
+@itemx -mno-small-exec
+@opindex msmall-exec
+@opindex mno-small-exec
+Generate (or do not generate) code using the @code{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 @code{basr} instruction instead,
+which does not have this limitation.
+
+@item -m64
+@itemx -m31
+@opindex m64
+@opindex m31
+When @option{-m31} is specified, generate code compliant to the
+Linux for S/390 ABI@. When @option{-m64} is specified, generate
+code compliant to the Linux for zSeries ABI@. This allows GCC in
+particular to generate 64-bit instructions. For the @samp{s390}
+targets, the default is @option{-m31}, while the @samp{s390x}
+targets default to @option{-m64}.
+
+@item -mmvcle
+@itemx -mno-mvcle
+@opindex mmvcle
+@opindex mno-mvcle
+Generate (or do not generate) code using the @code{mvcle} instruction
+to perform block moves. When @option{-mno-mvcle} is specifed,
+use a @code{mvc} loop instead. This is the default.
+
+@item -mdebug
+@itemx -mno-debug
+@opindex mdebug
+@opindex mno-debug
+Print (or do not print) additional debug information when compiling.
+The default is to not print debug information.
+
+@end table
+
+@node CRIS Options
+@subsection CRIS Options
+@cindex CRIS Options
+
+These options are defined specifically for the CRIS ports.
+
+@table @gcctabopt
+@item -march=@var{architecture-type}
+@itemx -mcpu=@var{architecture-type}
+@opindex march
+@opindex mcpu
+Generate code for the specified architecture. The choices for
+@var{architecture-type} are @samp{v3}, @samp{v8} and @samp{v10} for
+respectively ETRAX@w{ }4, ETRAX@w{ }100, and ETRAX@w{ }100@w{ }LX.
+Default is @samp{v0} except for cris-axis-linux-gnu, where the default is
+@samp{v10}.
+
+@item -mtune=@var{architecture-type}
+@opindex mtune
+Tune to @var{architecture-type} everything applicable about the generated
+code, except for the ABI and the set of available instructions. The
+choices for @var{architecture-type} are the same as for
+@option{-march=@var{architecture-type}}.
+
+@item -mmax-stack-frame=@var{n}
+@opindex mmax-stack-frame
+Warn when the stack frame of a function exceeds @var{n} bytes.
+
+@item -melinux-stacksize=@var{n}
+@opindex melinux-stacksize
+Only available with the @samp{cris-axis-aout} target. Arranges for
+indications in the program to the kernel loader that the stack of the
+program should be set to @var{n} bytes.
+
+@item -metrax4
+@itemx -metrax100
+@opindex metrax4
+@opindex metrax100
+The options @option{-metrax4} and @option{-metrax100} are synonyms for
+@option{-march=v3} and @option{-march=v8} respectively.
+
+@item -mpdebug
+@opindex mpdebug
+Enable CRIS-specific verbose debug-related information in the assembly
+code. This option also has the effect to turn off the @samp{#NO_APP}
+formatted-code indicator to the assembler at the beginning of the
+assembly file.
+
+@item -mcc-init
+@opindex mcc-init
+Do not use condition-code results from previous instruction; always emit
+compare and test instructions before use of condition codes.
+
+@item -mno-side-effects
+@opindex mno-side-effects
+Do not emit instructions with side-effects in addressing modes other than
+post-increment.
+
+@item -mstack-align
+@itemx -mno-stack-align
+@itemx -mdata-align
+@itemx -mno-data-align
+@itemx -mconst-align
+@itemx -mno-const-align
+@opindex mstack-align
+@opindex mno-stack-align
+@opindex mdata-align
+@opindex mno-data-align
+@opindex mconst-align
+@opindex mno-const-align
+These options (no-options) arranges (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.
+
+@item -m32-bit
+@itemx -m16-bit
+@itemx -m8-bit
+@opindex m32-bit
+@opindex m16-bit
+@opindex 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.
+
+@item -mno-prologue-epilogue
+@itemx -mprologue-epilogue
+@opindex mno-prologue-epilogue
+@opindex mprologue-epilogue
+With @option{-mno-prologue-epilogue}, the normal function prologue and
+epilogue that sets 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 variable needs to be allocated.
+
+@item -mno-gotplt
+@itemx -mgotplt
+@opindex mno-gotplt
+@opindex mgotplt
+With @option{-fpic} and @option{-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 @option{-mgotplt}.
+
+@item -maout
+@opindex maout
+Legacy no-op option only recognized with the cris-axis-aout target.
+
+@item -melf
+@opindex melf
+Legacy no-op option only recognized with the cris-axis-elf and
+cris-axis-linux-gnu targets.
+
+@item -melinux
+@opindex melinux
+Only recognized with the cris-axis-aout target, where it selects a
+GNU/linux-like multilib, include files and instruction set for
+@option{-march=v8}.
+
+@item -mlinux
+@opindex mlinux
+Legacy no-op option only recognized with the cris-axis-linux-gnu target.
+
+@item -sim
+@opindex sim
+This option, recognized for the cris-axis-aout and cris-axis-elf arranges
+to link with input-output functions from a simulator library. Code,
+initialized data and zero-initialized data are allocated consecutively.
+
+@item -sim2
+@opindex sim2
+Like @option{-sim}, but pass linker options to locate initialized data at
+0x40000000 and zero-initialized data at 0x80000000.
+@end table
+
+@node MMIX Options
+@subsection MMIX Options
+@cindex MMIX Options
+
+These options are defined for the MMIX:
+
+@table @gcctabopt
+@item -mlibfuncs
+@itemx -mno-libfuncs
+@opindex mlibfuncs
+@opindex mno-libfuncs
+Specify that intrinsic library functions are being compiled, passing all
+values in registers, no matter the size.
+
+@item -mepsilon
+@itemx -mno-epsilon
+@opindex mepsilon
+@opindex mno-epsilon
+Generate floating-point comparison instructions that compare with respect
+to the @code{rE} epsilon register.
+
+@item -mabi=mmixware
+@itemx -mabi=gnu
+@opindex mabi-mmixware
+@opindex mabi=gnu
+Generate code that passes function parameters and return values that (in
+the called function) are seen as registers @code{$0} and up, as opposed to
+the GNU ABI which uses global registers @code{$231} and up.
+
+@item -mzero-extend
+@itemx -mno-zero-extend
+@opindex mzero-extend
+@opindex 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.
+
+@item -mknuthdiv
+@itemx -mno-knuthdiv
+@opindex mknuthdiv
+@opindex mno-knuthdiv
+Make the result of a division yielding a remainder have the same sign as
+the divisor. With the default, @option{-mno-knuthdiv}, the sign of the
+remainder follows the sign of the dividend. Both methods are
+arithmetically valid, the latter being almost exclusively used.
+
+@item -mtoplevel-symbols
+@itemx -mno-toplevel-symbols
+@opindex mtoplevel-symbols
+@opindex mno-toplevel-symbols
+Prepend (do not prepend) a @samp{:} to all global symbols, so the assembly
+code can be used with the @code{PREFIX} assembly directive.
+
+@item -melf
+@opindex melf
+Generate an executable in the ELF format, rather than the default
+@samp{mmo} format used by the @command{mmix} simulator.
+
+@item -mbranch-predict
+@itemx -mno-branch-predict
+@opindex mbranch-predict
+@opindex mno-branch-predict
+Use (do not use) the probable-branch instructions, when static branch
+prediction indicates a probable branch.
+
+@item -mbase-addresses
+@itemx -mno-base-addresses
+@opindex mbase-addresses
+@opindex mno-base-addresses
+Generate (do not generate) code that uses @emph{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 @option{-mno-base-addresses}.
+@end table
+
+@node PDP-11 Options
+@subsection PDP-11 Options
+@cindex PDP-11 Options
+
+These options are defined for the PDP-11:
+
+@table @gcctabopt
+@item -mfpu
+@opindex mfpu
+Use hardware FPP floating point. This is the default. (FIS floating
+point on the PDP-11/40 is not supported.)
+
+@item -msoft-float
+@opindex msoft-float
+Do not use hardware floating point.
+
+@item -mac0
+@opindex mac0
+Return floating-point results in ac0 (fr0 in Unix assembler syntax).
+
+@item -mno-ac0
+@opindex mno-ac0
+Return floating-point results in memory. This is the default.
+
+@item -m40
+@opindex m40
+Generate code for a PDP-11/40.
+
+@item -m45
+@opindex m45
+Generate code for a PDP-11/45. This is the default.
+
+@item -m10
+@opindex m10
+Generate code for a PDP-11/10.
+
+@item -mbcopy-builtin
+@opindex bcopy-builtin
+Use inline @code{movstrhi} patterns for copying memory. This is the
+default.
+
+@item -mbcopy
+@opindex mbcopy
+Do not use inline @code{movstrhi} patterns for copying memory.
+
+@item -mint16
+@itemx -mno-int32
+@opindex mint16
+@opindex mno-int32
+Use 16-bit @code{int}. This is the default.
+
+@item -mint32
+@itemx -mno-int16
+@opindex mint32
+@opindex mno-int16
+Use 32-bit @code{int}.
+
+@item -mfloat64
+@itemx -mno-float32
+@opindex mfloat64
+@opindex mno-float32
+Use 64-bit @code{float}. This is the default.
+
+@item -mfloat32
+@item -mno-float64
+@opindex mfloat32
+@opindex mno-float64
+Use 32-bit @code{float}.
+
+@item -mabshi
+@opindex mabshi
+Use @code{abshi2} pattern. This is the default.
+
+@item -mno-abshi
+@opindex mno-abshi
+Do not use @code{abshi2} pattern.
+
+@item -mbranch-expensive
+@opindex mbranch-expensive
+Pretend that branches are expensive. This is for experimenting with
+code generation only.
+
+@item -mbranch-cheap
+@opindex mbranch-cheap
+Do not pretend that branches are expensive. This is the default.
+
+@item -msplit
+@opindex msplit
+Generate code for a system with split I&D.
+
+@item -mno-split
+@opindex mno-split
+Generate code for a system without split I&D. This is the default.
+
+@item -munix-asm
+@opindex munix-asm
+Use Unix assembler syntax. This is the default when configured for
+@samp{pdp11-*-bsd}.
+
+@item -mdec-asm
+@opindex mdec-asm
+Use DEC assembler syntax. This is the default when configured for any
+PDP-11 target other than @samp{pdp11-*-bsd}.
+@end table
+
+@node Xstormy16 Options
+@subsection Xstormy16 Options
+@cindex Xstormy16 Options
+
+These options are defined for Xstormy16:
+
+@table @gcctabopt
+@item -msim
+@opindex msim
+Choose startup files and linker script suitable for the simulator.
+@end table
+
+@node Xtensa Options
+@subsection Xtensa Options
+@cindex Xtensa Options
+
+The Xtensa architecture is designed to support many different
+configurations. The compiler's default options can be set to match a
+particular Xtensa configuration by copying a configuration file into the
+GCC sources when building GCC@. The options below may be used to
+override the default options.
+
+@table @gcctabopt
+@item -mbig-endian
+@itemx -mlittle-endian
+@opindex mbig-endian
+@opindex mlittle-endian
+Specify big-endian or little-endian byte ordering for the target Xtensa
+processor.
+
+@item -mdensity
+@itemx -mno-density
+@opindex mdensity
+@opindex mno-density
+Enable or disable use of the optional Xtensa code density instructions.
+
+@item -mmac16
+@itemx -mno-mac16
+@opindex mmac16
+@opindex mno-mac16
+Enable or disable use of the Xtensa MAC16 option. When enabled, GCC
+will generate MAC16 instructions from standard C code, with the
+limitation that it will use neither the MR register file nor any
+instruction that operates on the MR registers. When this option is
+disabled, GCC will translate 16-bit multiply/accumulate operations to a
+combination of core instructions and library calls, depending on whether
+any other multiplier options are enabled.
+
+@item -mmul16
+@itemx -mno-mul16
+@opindex mmul16
+@opindex mno-mul16
+Enable or disable use of the 16-bit integer multiplier option. When
+enabled, the compiler will generate 16-bit multiply instructions for
+multiplications of 16 bits or smaller in standard C code. When this
+option is disabled, the compiler will either use 32-bit multiply or
+MAC16 instructions if they are available or generate library calls to
+perform the multiply operations using shifts and adds.
+
+@item -mmul32
+@itemx -mno-mul32
+@opindex mmul32
+@opindex mno-mul32
+Enable or disable use of the 32-bit integer multiplier option. When
+enabled, the compiler will generate 32-bit multiply instructions for
+multiplications of 32 bits or smaller in standard C code. When this
+option is disabled, the compiler will generate library calls to perform
+the multiply operations using either shifts and adds or 16-bit multiply
+instructions if they are available.
+
+@item -mnsa
+@itemx -mno-nsa
+@opindex mnsa
+@opindex mno-nsa
+Enable or disable use of the optional normalization shift amount
+(@code{NSA}) instructions to implement the built-in @code{ffs} function.
+
+@item -mminmax
+@itemx -mno-minmax
+@opindex mminmax
+@opindex mno-minmax
+Enable or disable use of the optional minimum and maximum value
+instructions.
+
+@item -msext
+@itemx -mno-sext
+@opindex msext
+@opindex mno-sext
+Enable or disable use of the optional sign extend (@code{SEXT})
+instruction.
+
+@item -mbooleans
+@itemx -mno-booleans
+@opindex mbooleans
+@opindex mno-booleans
+Enable or disable support for the boolean register file used by Xtensa
+coprocessors. This is not typically useful by itself but may be
+required for other options that make use of the boolean registers (e.g.,
+the floating-point option).
+
+@item -mhard-float
+@itemx -msoft-float
+@opindex mhard-float
+@opindex msoft-float
+Enable or disable use of the floating-point option. When enabled, GCC
+generates floating-point instructions for 32-bit @code{float}
+operations. When this option is disabled, GCC generates library calls
+to emulate 32-bit floating-point operations using integer instructions.
+Regardless of this option, 64-bit @code{double} operations are always
+emulated with calls to library functions.
+
+@item -mfused-madd
+@itemx -mno-fused-madd
+@opindex mfused-madd
+@opindex 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 @emph{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.
+
+@item -mserialize-volatile
+@itemx -mno-serialize-volatile
+@opindex mserialize-volatile
+@opindex mno-serialize-volatile
+When this option is enabled, GCC inserts @code{MEMW} instructions before
+@code{volatile} memory references to guarantee sequential consistency.
+The default is @option{-mserialize-volatile}. Use
+@option{-mno-serialize-volatile} to omit the @code{MEMW} instructions.
+
+@item -mtext-section-literals
+@itemx -mno-text-section-literals
+@opindex mtext-section-literals
+@opindex mno-text-section-literals
+Control the treatment of literal pools. The default is
+@option{-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 @option{-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.
+
+@item -mtarget-align
+@itemx -mno-target-align
+@opindex mtarget-align
+@opindex 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 will be performed. The
+default is @option{-mtarget-align}. These options do not affect the
+treatment of auto-aligned instructions like @code{LOOP}, which the
+assembler will always align, either by widening density instructions or
+by inserting no-op instructions.
+
+@item -mlongcalls
+@itemx -mno-longcalls
+@opindex mlongcalls
+@opindex 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 @code{CALL}
+instruction into an @code{L32R} followed by a @code{CALLX} instruction.
+The default is @option{-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 will still show direct call
+instructions---look at the disassembled object code to see the actual
+instructions. Note that the assembler will use an indirect call for
+every cross-file call, not just those that really will be out of range.
+@end table
+
@node Code Gen Options
@section Options for Code Generation Conventions
@cindex code generation conventions
You will normally not enable this option; instead, a language processor
that needs this handling would enable it on your behalf.
+@item -fasynchronous-unwind-tables
+@opindex funwind-tables
+Generate unwind table in dwarf2 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).
+
@item -fpcc-struct-return
@opindex fpcc-struct-return
Return ``short'' @code{struct} and @code{union} values in memory like
@item -freg-struct-return
@opindex freg-struct-return
-Use the convention that @code{struct} and @code{union} values are
-returned in registers when possible. This is more efficient for small
-structures than @option{-fpcc-struct-return}.
+Return @code{struct} and @code{union} values in registers when possible.
+This is more efficient for small structures than
+@option{-fpcc-struct-return}.
-If you specify neither @option{-fpcc-struct-return} nor its contrary
+If you specify neither @option{-fpcc-struct-return} nor
@option{-freg-struct-return}, GCC defaults to whichever convention is
standard for the target. If there is no standard convention, GCC
-defaults to @option{-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.
+defaults to @option{-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.
@item -fshort-enums
@opindex fshort-enums
not want to use this option, since it makes the code suboptimal, and
the offsets of structure members won't agree with system libraries.
-@item -fcheck-memory-usage
-@opindex fcheck-memory-usage
-Generate extra code to check each memory access. GCC will generate
-code that is suitable for a detector of bad memory accesses such as
-@file{Checker}.
-
-Normally, you should compile all, or none, of your code with this option.
-
-If you do mix code compiled with and without this option,
-you must ensure that all code that has side effects
-and that is called by code compiled with this option
-is, itself, compiled with this option.
-If you do not, you might get erroneous messages from the detector.
-
-If you use functions from a library that have side-effects (such as
-@code{read}), you might not be able to recompile the library and
-specify this option. In that case, you can enable the
-@option{-fprefix-function-name} option, which requests GCC to encapsulate
-your code and make other functions look as if they were compiled with
-@option{-fcheck-memory-usage}. This is done by calling ``stubs'',
-which are provided by the detector. If you cannot find or build
-stubs for every function you call, you might have to specify
-@option{-fcheck-memory-usage} without @option{-fprefix-function-name}.
-
-If you specify this option, you can not use the @code{asm} or
-@code{__asm__} keywords in functions with memory checking enabled. GCC
-cannot understand what the @code{asm} statement may do, and therefore
-cannot generate the appropriate code, so it will reject it. However, if
-you specify the function attribute @code{no_check_memory_usage}
-(@pxref{Function Attributes}), GCC will disable memory checking within a
-function; you may use @code{asm} statements inside such functions. You
-may have an inline expansion of a non-checked function within a checked
-function; in that case GCC will not generate checks for the inlined
-function's memory accesses.
-
-If you move your @code{asm} statements to non-checked inline functions
-and they do access memory, you can add calls to the support code in your
-inline function, to indicate any reads, writes, or copies being done.
-These calls would be similar to those done in the stubs described above.
-
-@item -fprefix-function-name
-@opindex fprefix-function-name
-Request GCC to add a prefix to the symbols generated for function names.
-GCC adds a prefix to the names of functions defined as well as
-functions called. Code compiled with this option and code compiled
-without the option can't be linked together, unless stubs are used.
-
-If you compile the following code with @option{-fprefix-function-name}
-@example
-extern void bar (int);
-void
-foo (int a)
-@{
- return bar (a + 5);
-@}
-@end example
-
-@noindent
-GCC will compile the code as if it was written:
-@example
-extern void prefix_bar (int);
-void
-prefix_foo (int a)
-@{
- return prefix_bar (a + 5);
-@}
-@end example
-This option is designed to be used with @option{-fcheck-memory-usage}.
-
@item -finstrument-functions
@opindex finstrument-functions
Generate instrumentation calls for entry and exit to functions. Just
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 address @samp{0x80000000} and grows
-downwards you can use the flags
-@samp{-fstack-limit-symbol=__stack_limit
--Wl,--defsym,__stack_limit=0x7ffe0000} which will enforce a stack
-limit of 128K@.
+For instance, if the stack starts at absolute address @samp{0x80000000}
+and grows downwards, you can use the flags
+@option{-fstack-limit-symbol=__stack_limit} and
+@option{-Wl,--defsym,__stack_limit=0x7ffe0000} to enforce a stack limit
+of 128KB@. Note that this may only work with the GNU linker.
@cindex aliasing of parameters
@cindex parameters, aliased
parameters and global data.
@option{-fargument-alias} specifies that arguments (parameters) may
-alias each other and may alias global storage.
+alias each other and may alias global storage.@*
@option{-fargument-noalias} specifies that arguments do not alias
-each other, but may alias global storage.
+each other, but may alias global storage.@*
@option{-fargument-noalias-global} specifies that arguments do not
alias each other and do not alias global storage.
when searching for various kinds of files. Some are used to specify other
aspects of the compilation environment.
-@ifclear INTERNALS
-Note that you can also specify places to search using options such as
-@option{-B}, @option{-I} and @option{-L} (@pxref{Directory Options}). These
-take precedence over places specified using environment variables, which
-in turn take precedence over those specified by the configuration of GCC@.
-
-@end ifclear
-@ifset INTERNALS
Note that you can also specify places to search using options such as
@option{-B}, @option{-I} and @option{-L} (@pxref{Directory Options}). These
take precedence over places specified using environment variables, which
in turn take precedence over those specified by the configuration of GCC@.
-@xref{Driver}.
-@end ifset
+@xref{Driver,, Controlling the Compilation Driver @file{gcc}, gccint,
+GNU Compiler Collection (GCC) Internals}.
@table @env
@item LANG
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