This is Info file gcc.info, produced by Makeinfo version 1.68 from the
input file ./gcc.texi.

INFO-DIR-SECTION Programming
START-INFO-DIR-ENTRY
* gcc: (gcc). The GNU Compiler Collection.
END-INFO-DIR-ENTRY
This file documents the use and the internals of the GNU compiler.

Published by the Free Software Foundation 59 Temple Place - Suite 330
Boston, MA 02111-1307 USA

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 sections entitled "GNU General Public License" and "Funding
for Free Software" are included exactly as in the original, and
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Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that the sections entitled "GNU General Public
License" and "Funding for Free Software", and this permission notice,
may be included in translations approved by the Free Software Foundation
instead of in the original English.

File: gcc.info, Node: Directory Options, Next: Target Options, Prev: Link Options, Up: Invoking GCC

Options for Directory Search
============================

These options specify directories to search for header files, for
libraries and for parts of the compiler:

`-IDIR'
Add the directory DIR to the head of the list of directories to be
searched for header files. This can be used to override a system
header file, substituting your own version, since these
directories are searched before the system header file
directories. If you use more than one `-I' option, the
directories are scanned in left-to-right order; the standard
system directories come after.

`-I-'
Any directories you specify with `-I' options before the `-I-'
option are searched only for the case of `#include "FILE"'; they
are not searched for `#include <FILE>'.

If additional directories are specified with `-I' options after
the `-I-', these directories are searched for all `#include'
directives. (Ordinarily *all* `-I' directories are used this way.)

In addition, the `-I-' option inhibits the use of the current
directory (where the current input file came from) as the first
search directory for `#include "FILE"'. There is no way to
override this effect of `-I-'. With `-I.' you can specify
searching the directory which was current when the compiler was
invoked. That is not exactly the same as what the preprocessor
does by default, but it is often satisfactory.

`-I-' does not inhibit the use of the standard system directories
for header files. Thus, `-I-' and `-nostdinc' are independent.

`-LDIR'
Add directory DIR to the list of directories to be searched for
`-l'.

`-BPREFIX'
This option specifies where to find the executables, libraries,
include files, and data files of the compiler itself.

The compiler driver program runs one or more of the subprograms
`cpp', `cc1', `as' and `ld'. It tries PREFIX as a prefix for each
program it tries to run, both with and without `MACHINE/VERSION/'
(*note Target Options::.).

For each subprogram to be run, the compiler driver first tries the
`-B' prefix, if any. If that name is not found, or if `-B' was
not specified, the driver tries two standard prefixes, which are
`/usr/lib/gcc/' and `/usr/local/lib/gcc-lib/'. If neither of
those results in a file name that is found, the unmodified program
name is searched for using the directories specified in your
`PATH' environment variable.

`-B' prefixes that effectively specify directory names also apply
to libraries in the linker, because the compiler translates these
options into `-L' options for the linker. They also apply to
includes files in the preprocessor, because the compiler
translates these options into `-isystem' options for the
preprocessor. In this case, the compiler appends `include' to the
prefix.

The run-time support file `libgcc.a' can also be searched for using
the `-B' prefix, if needed. If it is not found there, the two
standard prefixes above are tried, and that is all. The file is
left out of the link if it is not found by those means.

Another way to specify a prefix much like the `-B' prefix is to use
the environment variable `GCC_EXEC_PREFIX'. *Note Environment
Variables::.

`-specs=FILE'
Process FILE after the compiler reads in the standard `specs'
file, in order to override the defaults that the `gcc' driver
program uses when determining what switches to pass to `cc1',
`cc1plus', `as', `ld', etc. More than one `-specs='FILE can be
specified on the command line, and they are processed in order,
from left to right.

File: gcc.info, Node: Target Options, Next: Submodel Options, Prev: Directory Options, Up: Invoking GCC

Specifying Target Machine and Compiler Version
==============================================

By default, GCC compiles code for the same type of machine that you
are using. However, it can also be installed as a cross-compiler, to
compile for some other type of machine. In fact, several different
configurations of GCC, for different target machines, can be installed
side by side. Then you specify which one to use with the `-b' option.

In addition, older and newer versions of GCC can be installed side
by side. One of them (probably the newest) will be the default, but
you may sometimes wish to use another.

`-b MACHINE'
The argument MACHINE specifies the target machine for compilation.
This is useful when you have installed GCC as a cross-compiler.

The value to use for MACHINE is the same as was specified as the
machine type when configuring GCC as a cross-compiler. For
example, if a cross-compiler was configured with `configure
i386v', meaning to compile for an 80386 running System V, then you
would specify `-b i386v' to run that cross compiler.

When you do not specify `-b', it normally means to compile for the
same type of machine that you are using.

`-V VERSION'
The argument VERSION specifies which version of GCC to run. This
is useful when multiple versions are installed. For example,
VERSION might be `2.0', meaning to run GCC version 2.0.

The default version, when you do not specify `-V', is the last
version of GCC that you installed.

The `-b' and `-V' options actually work by controlling part of the
file name used for the executable files and libraries used for
compilation. A given version of GCC, for a given target machine, is
normally kept in the directory `/usr/local/lib/gcc-lib/MACHINE/VERSION'.

Thus, sites can customize the effect of `-b' or `-V' either by
changing the names of these directories or adding alternate names (or
symbolic links). If in directory `/usr/local/lib/gcc-lib/' the file
`80386' is a link to the file `i386v', then `-b 80386' becomes an alias
for `-b i386v'.

In one respect, the `-b' or `-V' do not completely change to a
different compiler: the top-level driver program `gcc' that you
originally invoked continues to run and invoke the other executables
(preprocessor, compiler per se, assembler and linker) that do the real
work. However, since no real work is done in the driver program, it
usually does not matter that the driver program in use is not the one
for the specified target and version.

The only way that the driver program depends on the target machine is
in the parsing and handling of special machine-specific options.
However, this is controlled by a file which is found, along with the
other executables, in the directory for the specified version and
target machine. As a result, a single installed driver program adapts
to any specified target machine and compiler version.

The driver program executable does control one significant thing,
however: the default version and target machine. Therefore, you can
install different instances of the driver program, compiled for
different targets or versions, under different names.

For example, if the driver for version 2.0 is installed as `ogcc'
and that for version 2.1 is installed as `gcc', then the command `gcc'
will use version 2.1 by default, while `ogcc' will use 2.0 by default.
However, you can choose either version with either command with the
`-V' option.

File: gcc.info, Node: Submodel Options, Next: Code Gen Options, Prev: Target Options, Up: Invoking GCC

Hardware Models and Configurations
==================================

Earlier we discussed the standard option `-b' which chooses among
different installed compilers for completely different target machines,
such as Vax vs. 68000 vs. 80386.

In addition, each of these target machine types can have its own
special options, starting with `-m', to choose among various hardware
models or configurations--for example, 68010 vs 68020, floating
coprocessor or none. A single installed version of the compiler can
compile for any model or configuration, according to the options
specified.

Some configurations of the compiler also support additional special
options, usually for compatibility with other compilers on the same
platform.

These options are defined by the macro `TARGET_SWITCHES' in the
machine description. The default for the options is also defined by
that macro, which enables you to change the defaults.

* Menu:

* M680x0 Options::
* VAX Options::
* SPARC Options::
* Convex Options::
* AMD29K Options::
* ARM Options::
* Thumb Options::
* MN10200 Options::
* MN10300 Options::
* M32R/D Options::
* M88K Options::
* RS/6000 and PowerPC Options::
* RT Options::
* MIPS Options::
* i386 Options::
* HPPA Options::
* Intel 960 Options::
* DEC Alpha Options::
* Clipper Options::
* H8/300 Options::
* SH Options::
* System V Options::
* TMS320C3x/C4x Options::
* V850 Options::
* ARC Options::
* NS32K Options::

File: gcc.info, Node: M680x0 Options, Next: VAX Options, Up: Submodel Options

M680x0 Options
--------------

These are the `-m' options defined for the 68000 series. The default
values for these options depends on which style of 68000 was selected
when the compiler was configured; the defaults for the most common
choices are given below.

`-m68000'
`-mc68000'
Generate output for a 68000. This is the default when the
compiler is configured for 68000-based systems.

Use this option for microcontrollers with a 68000 or EC000 core,
including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.

`-m68020'
`-mc68020'
Generate output for a 68020. This is the default when the
compiler is configured for 68020-based systems.

`-m68881'
Generate output containing 68881 instructions for floating point.
This is the default for most 68020 systems unless `-nfp' was
specified when the compiler was configured.

`-m68030'
Generate output for a 68030. This is the default when the
compiler is configured for 68030-based systems.

`-m68040'
Generate output for a 68040. This is the default when the
compiler is configured for 68040-based systems.

This option inhibits the use of 68881/68882 instructions that have
to be emulated by software on the 68040. Use this option if your
68040 does not have code to emulate those instructions.

`-m68060'
Generate output for a 68060. This is the default when the
compiler is configured for 68060-based systems.

This option inhibits the use of 68020 and 68881/68882 instructions
that have to be emulated by software on the 68060. Use this
option if your 68060 does not have code to emulate those
instructions.

`-mcpu32'
Generate output for a CPU32. This is the default when the compiler
is configured for CPU32-based systems.

Use this option for microcontrollers with a CPU32 or CPU32+ core,
including the 68330, 68331, 68332, 68333, 68334, 68336, 68340,
68341, 68349 and 68360.

`-m5200'
Generate output for a 520X "coldfire" family cpu. This is the
default when the compiler is configured for 520X-based systems.

Use this option for microcontroller with a 5200 core, including
the MCF5202, MCF5203, MCF5204 and MCF5202.

`-m68020-40'
Generate output for a 68040, without using any of the new
instructions. This results in code which can run relatively
efficiently on either a 68020/68881 or a 68030 or a 68040. The
generated code does use the 68881 instructions that are emulated
on the 68040.

`-m68020-60'
Generate output for a 68060, without using any of the new
instructions. This results in code which can run relatively
efficiently on either a 68020/68881 or a 68030 or a 68040. The
generated code does use the 68881 instructions that are emulated
on the 68060.

`-mfpa'
Generate output containing Sun FPA instructions for floating point.

`-msoft-float'
Generate output containing library calls for floating point.
*Warning:* the requisite libraries are not available for all m68k
targets. Normally the facilities of the machine's usual C
compiler are used, but this can't be done directly in
cross-compilation. You must make your own arrangements to provide
suitable library functions for cross-compilation. The embedded
targets `m68k-*-aout' and `m68k-*-coff' do provide software
floating point support.

`-mshort'
Consider type `int' to be 16 bits wide, like `short int'.

`-mnobitfield'
Do not use the bit-field instructions. The `-m68000', `-mcpu32'
and `-m5200' options imply `-mnobitfield'.

`-mbitfield'
Do use the bit-field instructions. The `-m68020' option implies
`-mbitfield'. This is the default if you use a configuration
designed for a 68020.

`-mrtd'
Use a different function-calling convention, in which functions
that take a fixed number of arguments return with the `rtd'
instruction, which pops their arguments while returning. This
saves one instruction in the caller since there is no need to pop
the arguments there.

This calling convention is incompatible with the one normally used
on Unix, so you cannot use it if you need to call libraries
compiled with the Unix compiler.

Also, you must provide function prototypes for all functions that
take variable numbers of arguments (including `printf'); otherwise
incorrect code will be generated for calls to those functions.

In addition, seriously incorrect code will result if you call a
function with too many arguments. (Normally, extra arguments are
harmlessly ignored.)

The `rtd' instruction is supported by the 68010, 68020, 68030,
68040, 68060 and CPU32 processors, but not by the 68000 or 5200.

`-malign-int'
`-mno-align-int'
Control whether GCC aligns `int', `long', `long long', `float',
`double', and `long double' variables on a 32-bit boundary
(`-malign-int') or a 16-bit boundary (`-mno-align-int'). Aligning
variables on 32-bit boundaries produces code that runs somewhat
faster on processors with 32-bit busses at the expense of more
memory.

*Warning:* if you use the `-malign-int' switch, GCC will align
structures containing the above types differently than most
published application binary interface specifications for the m68k.

File: gcc.info, Node: VAX Options, Next: SPARC Options, Prev: M680x0 Options, Up: Submodel Options

VAX Options
-----------

These `-m' options are defined for the Vax:

`-munix'
Do not output certain jump instructions (`aobleq' and so on) that
the Unix assembler for the Vax cannot handle across long ranges.

`-mgnu'
Do output those jump instructions, on the assumption that you will
assemble with the GNU assembler.

`-mg'
Output code for g-format floating point numbers instead of
d-format.

File: gcc.info, Node: SPARC Options, Next: Convex Options, Prev: VAX Options, Up: Submodel Options

SPARC Options
-------------

These `-m' switches are supported on the SPARC:

`-mno-app-regs'
`-mapp-regs'
Specify `-mapp-regs' to generate output using the global registers
2 through 4, which the SPARC SVR4 ABI reserves for applications.
This is the default.

To be fully SVR4 ABI compliant at the cost of some performance
loss, specify `-mno-app-regs'. You should compile libraries and
system software with this option.

`-mfpu'
`-mhard-float'
Generate output containing floating point instructions. This is
the default.

`-mno-fpu'
`-msoft-float'
Generate output containing library calls for floating point.
*Warning:* the requisite libraries are not available for all SPARC
targets. Normally the facilities of the machine's usual C
compiler are used, but this cannot be done directly in
cross-compilation. You must make your own arrangements to provide
suitable library functions for cross-compilation. The embedded
targets `sparc-*-aout' and `sparclite-*-*' do provide software
floating point support.

`-msoft-float' changes the calling convention in the output file;
therefore, it is only useful if you compile *all* of a program with
this option. In particular, you need to compile `libgcc.a', the
library that comes with GCC, with `-msoft-float' in order for this
to work.

`-mhard-quad-float'
Generate output containing quad-word (long double) floating point
instructions.

`-msoft-quad-float'
Generate output containing library calls for quad-word (long
double) floating point instructions. The functions called are
those specified in the SPARC ABI. This is the default.

As of this writing, there are no sparc implementations that have
hardware support for the quad-word floating point instructions.
They all invoke a trap handler for one of these instructions, and
then the trap handler emulates the effect of the instruction.
Because of the trap handler overhead, this is much slower than
calling the ABI library routines. Thus the `-msoft-quad-float'
option is the default.

`-mno-epilogue'
`-mepilogue'
With `-mepilogue' (the default), the compiler always emits code for
function exit at the end of each function. Any function exit in
the middle of the function (such as a return statement in C) will
generate a jump to the exit code at the end of the function.

With `-mno-epilogue', the compiler tries to emit exit code inline
at every function exit.

`-mno-flat'
`-mflat'
With `-mflat', the compiler does not generate save/restore
instructions and will use a "flat" or single register window
calling convention. This model uses %i7 as the frame pointer and
is compatible with the normal register window model. Code from
either may be intermixed. The local registers and the input
registers (0-5) are still treated as "call saved" registers and
will be saved on the stack as necessary.

With `-mno-flat' (the default), the compiler emits save/restore
instructions (except for leaf functions) and is the normal mode of
operation.

`-mno-unaligned-doubles'
`-munaligned-doubles'
Assume that doubles have 8 byte alignment. This is the default.

With `-munaligned-doubles', GCC assumes that doubles have 8 byte
alignment only if they are contained in another type, or if they
have an absolute address. Otherwise, it assumes they have 4 byte
alignment. Specifying this option avoids some rare compatibility
problems with code generated by other compilers. It is not the
default because it results in a performance loss, especially for
floating point code.

`-mv8'
`-msparclite'
These two options select variations on the SPARC architecture.

By default (unless specifically configured for the Fujitsu
SPARClite), GCC generates code for the v7 variant of the SPARC
architecture.

`-mv8' will give you SPARC v8 code. The only difference from v7
code is that the compiler emits the integer multiply and integer
divide instructions which exist in SPARC v8 but not in SPARC v7.

`-msparclite' will give you SPARClite code. This adds the integer
multiply, integer divide step and scan (`ffs') instructions which
exist in SPARClite but not in SPARC v7.

These options are deprecated and will be deleted in a future GCC
release. They have been replaced with `-mcpu=xxx'.

`-mcypress'
`-msupersparc'
These two options select the processor for which the code is
optimised.

With `-mcypress' (the default), the compiler optimizes code for the
Cypress CY7C602 chip, as used in the SparcStation/SparcServer 3xx
series. This is also appropriate for the older SparcStation 1, 2,
IPX etc.

With `-msupersparc' the compiler optimizes code for the SuperSparc
cpu, as used in the SparcStation 10, 1000 and 2000 series. This
flag also enables use of the full SPARC v8 instruction set.

These options are deprecated and will be deleted in a future GCC
release. They have been replaced with `-mcpu=xxx'.

`-mcpu=CPU_TYPE'
Set the instruction set, register set, and instruction scheduling
parameters for machine type CPU_TYPE. Supported values for
CPU_TYPE are `v7', `cypress', `v8', `supersparc', `sparclite',
`hypersparc', `sparclite86x', `f930', `f934', `sparclet',
`tsc701', `v9', and `ultrasparc'.

Default instruction scheduling parameters are used for values that
select an architecture and not an implementation. These are `v7',
`v8', `sparclite', `sparclet', `v9'.

Here is a list of each supported architecture and their supported
implementations.

v7: cypress
v8: supersparc, hypersparc
sparclite: f930, f934, sparclite86x
sparclet: tsc701
v9: ultrasparc

`-mtune=CPU_TYPE'
Set the instruction scheduling parameters for machine type
CPU_TYPE, but do not set the instruction set or register set that
the option `-mcpu='CPU_TYPE would.

The same values for `-mcpu='CPU_TYPE are used for `-mtune='
CPU_TYPE, though the only useful values are those that select a
particular cpu implementation: `cypress', `supersparc',
`hypersparc', `f930', `f934', `sparclite86x', `tsc701',
`ultrasparc'.

`-malign-loops=NUM'
Align loops to a 2 raised to a NUM byte boundary. If
`-malign-loops' is not specified, the default is 2.

`-malign-jumps=NUM'
Align instructions that are only jumped to to a 2 raised to a NUM
byte boundary. If `-malign-jumps' is not specified, the default
is 2.

`-malign-functions=NUM'
Align the start of functions to a 2 raised to NUM byte boundary.
If `-malign-functions' is not specified, the default is 2 if
compiling for 32 bit sparc, and 5 if compiling for 64 bit sparc.

These `-m' switches are supported in addition to the above on the
SPARCLET processor.

`-mlittle-endian'
Generate code for a processor running in little-endian mode.

`-mlive-g0'
Treat register `%g0' as a normal register. GCC will continue to
clobber it as necessary but will not assume it always reads as 0.

`-mbroken-saverestore'
Generate code that does not use non-trivial forms of the `save' and
`restore' instructions. Early versions of the SPARCLET processor
do not correctly handle `save' and `restore' instructions used with
arguments. They correctly handle them used without arguments. A
`save' instruction used without arguments increments the current
window pointer but does not allocate a new stack frame. It is
assumed that the window overflow trap handler will properly handle
this case as will interrupt handlers.

These `-m' switches are supported in addition to the above on SPARC
V9 processors in 64 bit environments.

`-mlittle-endian'
Generate code for a processor running in little-endian mode.

`-m32'
`-m64'
Generate code for a 32 bit or 64 bit environment. The 32 bit
environment sets int, long and pointer to 32 bits. The 64 bit
environment sets int to 32 bits and long and pointer to 64 bits.

`-mcmodel=medlow'
Generate code for the Medium/Low code model: the program must be
linked in the low 32 bits of the address space. Pointers are 64
bits. Programs can be statically or dynamically linked.

`-mcmodel=medmid'
Generate code for the Medium/Middle code model: the program must
be linked in the low 44 bits of the address space, the text
segment must be less than 2G bytes, and data segment must be
within 2G of the text segment. Pointers are 64 bits.

`-mcmodel=medany'
Generate code for the Medium/Anywhere code model: the program may
be linked anywhere in the address space, the text segment must be
less than 2G bytes, and data segment must be within 2G of the text
segment. Pointers are 64 bits.

`-mcmodel=embmedany'
Generate code for the Medium/Anywhere code model for embedded
systems: assume a 32 bit text and a 32 bit data segment, both
starting anywhere (determined at link time). Register %g4 points
to the base of the data segment. Pointers still 64 bits.
Programs are statically linked, PIC is not supported.

`-mstack-bias'
`-mno-stack-bias'
With `-mstack-bias', GCC assumes that the stack pointer, and frame
pointer if present, are offset by -2047 which must be added back
when making stack frame references. Otherwise, assume no such
offset is present.

File: gcc.info, Node: Convex Options, Next: AMD29K Options, Prev: SPARC Options, Up: Submodel Options

Convex Options
--------------

These `-m' options are defined for Convex:

`-mc1'
Generate output for C1. The code will run on any Convex machine.
The preprocessor symbol `__convex__c1__' is defined.

`-mc2'
Generate output for C2. Uses instructions not available on C1.
Scheduling and other optimizations are chosen for max performance
on C2. The preprocessor symbol `__convex_c2__' is defined.

`-mc32'
Generate output for C32xx. Uses instructions not available on C1.
Scheduling and other optimizations are chosen for max performance
on C32. The preprocessor symbol `__convex_c32__' is defined.

`-mc34'
Generate output for C34xx. Uses instructions not available on C1.
Scheduling and other optimizations are chosen for max performance
on C34. The preprocessor symbol `__convex_c34__' is defined.

`-mc38'
Generate output for C38xx. Uses instructions not available on C1.
Scheduling and other optimizations are chosen for max performance
on C38. The preprocessor symbol `__convex_c38__' is defined.

`-margcount'
Generate code which puts an argument count in the word preceding
each argument list. This is compatible with regular CC, and a few
programs may need the argument count word. GDB and other
source-level debuggers do not need it; this info is in the symbol
table.

`-mnoargcount'
Omit the argument count word. This is the default.

`-mvolatile-cache'
Allow volatile references to be cached. This is the default.

`-mvolatile-nocache'
Volatile references bypass the data cache, going all the way to
memory. This is only needed for multi-processor code that does
not use standard synchronization instructions. Making
non-volatile references to volatile locations will not necessarily
work.

`-mlong32'
Type long is 32 bits, the same as type int. This is the default.

`-mlong64'
Type long is 64 bits, the same as type long long. This option is
useless, because no library support exists for it.

File: gcc.info, Node: AMD29K Options, Next: ARM Options, Prev: Convex Options, Up: Submodel Options

AMD29K Options
--------------

These `-m' options are defined for the AMD Am29000:

`-mdw'
Generate code that assumes the `DW' bit is set, i.e., that byte and
halfword operations are directly supported by the hardware. This
is the default.

`-mndw'
Generate code that assumes the `DW' bit is not set.

`-mbw'
Generate code that assumes the system supports byte and halfword
write operations. This is the default.

`-mnbw'
Generate code that assumes the systems does not support byte and
halfword write operations. `-mnbw' implies `-mndw'.

`-msmall'
Use a small memory model that assumes that all function addresses
are either within a single 256 KB segment or at an absolute
address of less than 256k. This allows the `call' instruction to
be used instead of a `const', `consth', `calli' sequence.

`-mnormal'
Use the normal memory model: Generate `call' instructions only when
calling functions in the same file and `calli' instructions
otherwise. This works if each file occupies less than 256 KB but
allows the entire executable to be larger than 256 KB. This is
the default.

`-mlarge'
Always use `calli' instructions. Specify this option if you expect
a single file to compile into more than 256 KB of code.

`-m29050'
Generate code for the Am29050.

`-m29000'
Generate code for the Am29000. This is the default.

`-mkernel-registers'
Generate references to registers `gr64-gr95' instead of to
registers `gr96-gr127'. This option can be used when compiling
kernel code that wants a set of global registers disjoint from
that used by user-mode code.

Note that when this option is used, register names in `-f' flags
must use the normal, user-mode, names.

`-muser-registers'
Use the normal set of global registers, `gr96-gr127'. This is the
default.

`-mstack-check'
`-mno-stack-check'
Insert (or do not insert) a call to `__msp_check' after each stack
adjustment. This is often used for kernel code.

`-mstorem-bug'
`-mno-storem-bug'
`-mstorem-bug' handles 29k processors which cannot handle the
separation of a mtsrim insn and a storem instruction (most 29000
chips to date, but not the 29050).

`-mno-reuse-arg-regs'
`-mreuse-arg-regs'
`-mno-reuse-arg-regs' tells the compiler to only use incoming
argument registers for copying out arguments. This helps detect
calling a function with fewer arguments than it was declared with.

`-mno-impure-text'
`-mimpure-text'
`-mimpure-text', used in addition to `-shared', tells the compiler
to not pass `-assert pure-text' to the linker when linking a
shared object.

`-msoft-float'
Generate output containing library calls for floating point.
*Warning:* the requisite libraries are not part of GCC. Normally
the facilities of the machine's usual C compiler are used, but
this can't be done directly in cross-compilation. You must make
your own arrangements to provide suitable library functions for
cross-compilation.

`-mno-multm'
Do not generate multm or multmu instructions. This is useful for
some embedded systems which do not have trap handlers for these
instructions.

File: gcc.info, Node: ARM Options, Next: Thumb Options, Prev: AMD29K Options, Up: Submodel Options

ARM Options
-----------

These `-m' options are defined for Advanced RISC Machines (ARM)
architectures:

`-mapcs-frame'
Generate a stack frame that is compliant with the ARM Procedure
Call Standard for all functions, even if this is not strictly
necessary for correct execution of the code. Specifying
`-fomit-frame-pointer' with this option will cause the stack
frames not to be generated for leaf functions. The default is
`-mno-apcs-frame'.

`-mapcs'
This is a synonym for `-mapcs-frame'.

`-mapcs-26'
Generate code for a processor running with a 26-bit program
counter, and conforming to the function calling standards for the
APCS 26-bit option. This option replaces the `-m2' and `-m3'
options of previous releases of the compiler.

`-mapcs-32'
Generate code for a processor running with a 32-bit program
counter, and conforming to the function calling standards for the
APCS 32-bit option. This option replaces the `-m6' option of
previous releases of the compiler.

`-mapcs-stack-check'
Generate code to check the amount of stack space available upon
entry to every function (that actually uses some stack space). If
there is insufficient space available then either the function
`__rt_stkovf_split_small' or `__rt_stkovf_split_big' will be
called, depending upon the amount of stack space required. The
run time system is required to provide these functions. The
default is `-mno-apcs-stack-check', since this produces smaller
code.

`-mapcs-float'
Pass floating point arguments using the float point registers.
This is one of the variants of the APCS. This option is
reccommended if the target hardware has a floating point unit or
if a lot of floating point arithmetic is going to be performed by
the code. The default is `-mno-apcs-float', since integer only
code is slightly increased in size if `-mapcs-float' is used.

`-mapcs-reentrant'
Generate reentrant, position independent code. This is the
equivalent to specifying the `-fpic' option. The default is
`-mno-apcs-reentrant'.

`-mthumb-interwork'
Generate code which supports calling between the ARM and THUMB
instruction sets. Without this option the two instruction sets
cannot be reliably used inside one program. The default is
`-mno-thumb-interwork', since slightly larger code is generated
when `-mthumb-interwork' is specified.

`-mno-sched-prolog'
Prevent the reordering of instructions in the function prolog, or
the merging of those instruction with the instructions in the
function's body. This means that all functions will start with a
recognisable set of instructions (or in fact one of a chioce from
a small set of different function prologues), and this information
can be used to locate the start if functions inside an executable
piece of code. The default is `-msched-prolog'.

`-mhard-float'
Generate output containing floating point instructions. This is
the default.

`-msoft-float'
Generate output containing library calls for floating point.
*Warning:* the requisite libraries are not available for all ARM
targets. Normally the facilities of the machine's usual C
compiler are used, but this cannot be done directly in
cross-compilation. You must make your own arrangements to provide
suitable library functions for cross-compilation.

`-mlittle-endian'
Generate code for a processor running in little-endian mode. This
is the default for all standard configurations.

`-mbig-endian'
Generate code for a processor running in big-endian mode; the
default is to compile code for a little-endian processor.

`-mwords-little-endian'
This option only applies when generating code for big-endian
processors. Generate code for a little-endian word order but a
big-endian byte order. That is, a byte order of the form
`32107654'. Note: this option should only be used if you require
compatibility with code for big-endian ARM processors generated by
versions of the compiler prior to 2.8.

`-mshort-load-bytes'
Do not try to load half-words (eg `short's) by loading a word from
an unaligned address. For some targets the MMU is configured to
trap unaligned loads; use this option to generate code that is
safe in these environments.

`-mno-short-load-bytes'
Use unaligned word loads to load half-words (eg `short's). This
option produces more efficient code, but the MMU is sometimes
configured to trap these instructions.

`-mshort-load-words'
This is a synonym for the `-mno-short-load-bytes'.

`-mno-short-load-words'
This is a synonym for the `-mshort-load-bytes'.

`-mbsd'
This option only applies to RISC iX. Emulate the native BSD-mode
compiler. This is the default if `-ansi' is not specified.

`-mxopen'
This option only applies to RISC iX. Emulate the native
X/Open-mode compiler.

`-mno-symrename'
This option only applies to RISC iX. Do not run the assembler
post-processor, `symrename', after code has been assembled.
Normally it is necessary to modify some of the standard symbols in
preparation for linking with the RISC iX C library; this option
suppresses this pass. The post-processor is never run when the
compiler is built for cross-compilation.

`-mcpu=<name>'
`-mtune=<name>'
This specifies the name of the target ARM processor. GCC uses
this name to determine what kind of instructions it can use when
generating assembly code. Permissable names are: arm2, arm250,
arm3, arm6, arm60, arm600, arm610, arm620, arm7, arm7m, arm7d,
arm7dm, arm7di, arm7dmi, arm70, arm700, arm700i, arm710, arm710c,
arm7100, arm7500, arm7500fe, arm7tdmi, arm8, strongarm,
strongarm110, strongarm1100, arm8, arm810, arm9, arm9tdmi.
`-mtune=' is a synonym for `-mcpue=' to support older versions of
GCC.

`-march=<name>'
This specifies the name of the target ARM architecture. GCC uses
this name to determine what kind of instructions it can use when
generating assembly code. This option can be used in conjunction
with or instead of the `-mcpu=' option. Permissable names are:
armv2, armv2a, armv3, armv3m, armv4, armv4t

`-mfpe=<number>'
`-mfp=<number>'
This specifes the version of the floating point emulation
available on the target. Permissable values are 2 and 3. `-mfp='
is a synonym for `-mfpe=' to support older versions of GCC.

`-mstructure-size-boundary=<n>'
The size of all structures and unions will be rounded up to a
multiple of the number of bits set by this option. Permissable
values are 8 and 32. The default value varies for different
toolchains. For the COFF targeted toolchain the default value is
8. Specifying the larger number can produced faster, more
efficient code, but can also increase the size of the program.
The two values are potentially incompatible. Code compiled with
one value cannot necessarily expect to work with code or libraries
compiled with the other value, if they exchange information using
structures or unions. Programmers are encouraged to use the 32
value as future versions of the toolchain may default to this
value.

`-mabort-on-noreturn'
Generate a call to the function abort at the end of a noreturn
function. It will be executed if the function tries to return.

File: gcc.info, Node: Thumb Options, Next: MN10200 Options, Prev: ARM Options, Up: Submodel Options

Thumb Options
-------------

`-mthumb-interwork'
Generate code which supports calling between the THUMB and ARM
instruction sets. Without this option the two instruction sets
cannot be reliably used inside one program. The default is
`-mno-thumb-interwork', since slightly smaller code is generated
with this option.

`-mtpcs-frame'
Generate a stack frame that is compliant with the Thumb Procedure
Call Standard for all non-leaf functions. (A leaf function is one
that does not call any other functions). The default is
`-mno-apcs-frame'.

`-mtpcs-leaf-frame'
Generate a stack frame that is compliant with the Thumb Procedure
Call Standard for all leaf functions. (A leaf function is one
that does not call any other functions). The default is
`-mno-apcs-leaf-frame'.

`-mlittle-endian'
Generate code for a processor running in little-endian mode. This
is the default for all standard configurations.

`-mbig-endian'
Generate code for a processor running in big-endian mode.

File: gcc.info, Node: MN10200 Options, Next: MN10300 Options, Prev: Thumb Options, Up: Submodel Options

MN10200 Options
---------------

These `-m' options are defined for Matsushita MN10200 architectures:
`-mrelax'
Indicate to the linker that it should perform a relaxation
optimization pass to shorten branches, calls and absolute memory
addresses. This option only has an effect when used on the
command line for the final link step.

This option makes symbolic debugging impossible.

File: gcc.info, Node: MN10300 Options, Next: M32R/D Options, Prev: MN10200 Options, Up: Submodel Options

MN10300 Options
---------------

These `-m' options are defined for Matsushita MN10300 architectures:

`-mmult-bug'
Generate code to avoid bugs in the multiply instructions for the
MN10300 processors. This is the default.

`-mno-mult-bug'
Do not generate code to avoid bugs in the multiply instructions
for the MN10300 processors.

`-mrelax'
Indicate to the linker that it should perform a relaxation
optimization pass to shorten branches, calls and absolute memory
addresses. This option only has an effect when used on the
command line for the final link step.

This option makes symbolic debugging impossible.

File: gcc.info, Node: M32R/D Options, Next: M88K Options, Prev: MN10300 Options, Up: Submodel Options

M32R/D Options
--------------

These `-m' options are defined for Mitsubishi M32R/D architectures:

`-mcode-model=small'
Assume all objects live in the lower 16MB of memory (so that their
addresses can be loaded with the `ld24' instruction), and assume
all subroutines are reachable with the `bl' instruction. This is
the default.

The addressability of a particular object can be set with the
`model' attribute.

`-mcode-model=medium'
Assume objects may be anywhere in the 32 bit address space (the
compiler will generate `seth/add3' instructions to load their
addresses), and assume all subroutines are reachable with the `bl'
instruction.

`-mcode-model=large'
Assume objects may be anywhere in the 32 bit address space (the
compiler will generate `seth/add3' instructions to load their
addresses), and assume subroutines may not be reachable with the
`bl' instruction (the compiler will generate the much slower
`seth/add3/jl' instruction sequence).

`-msdata=none'
Disable use of the small data area. Variables will be put into
one of `.data', `bss', or `.rodata' (unless the `section'
attribute has been specified). This is the default.

The small data area consists of sections `.sdata' and `.sbss'.
Objects may be explicitly put in the small data area with the
`section' attribute using one of these sections.

`-msdata=sdata'
Put small global and static data in the small data area, but do not
generate special code to reference them.

`-msdata=use'
Put small global and static data in the small data area, and
generate special instructions to reference them.

`-G NUM'
Put global and static objects less than or equal to NUM bytes into
the small data or bss sections instead of the normal data or bss
sections. The default value of NUM is 8. The `-msdata' option
must be set to one of `sdata' or `use' for this option to have any
effect.

All modules should be compiled with the same `-G NUM' value.
Compiling with different values of NUM may or may not work; if it
doesn't the linker will give an error message - incorrect code
will not be generated.