rs-6000-and-powerpc-options.html

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<code>-msoft-float</code> option, and pass the option to GCC when linking.

     <br><dt><code>-mmultiple</code>
     <dd><dt><code>-mno-multiple</code>
     <dd>Generate code that uses (does not use) the load multiple word
instructions and the store multiple word instructions.  These
instructions are generated by default on POWER systems, and not
generated on PowerPC systems.  Do not use <code>-mmultiple</code> on little
endian PowerPC systems, since those instructions do not work when the
processor is in little endian mode.  The exceptions are PPC740 and
PPC750 which permit the instructions usage in little endian mode.

     <br><dt><code>-mstring</code>
     <dd><dt><code>-mno-string</code>
     <dd>Generate code that uses (does not use) the load string instructions
and the store string word instructions to save multiple registers and
do small block moves.  These instructions are generated by default on
POWER systems, and not generated on PowerPC systems.  Do not use
<code>-mstring</code> on little endian PowerPC systems, since those
instructions do not work when the processor is in little endian mode. 
The exceptions are PPC740 and PPC750 which permit the instructions
usage in little endian mode.

     <br><dt><code>-mupdate</code>
     <dd><dt><code>-mno-update</code>
     <dd>Generate code that uses (does not use) the load or store instructions
that update the base register to the address of the calculated memory
location.  These instructions are generated by default.  If you use
<code>-mno-update</code>, there is a small window between the time that the
stack pointer is updated and the address of the previous frame is
stored, which means code that walks the stack frame across interrupts or
signals may get corrupted data.

     <br><dt><code>-mfused-madd</code>
     <dd><dt><code>-mno-fused-madd</code>
     <dd>Generate code that uses (does not use) the floating point multiply and
accumulate instructions.  These instructions are generated by default if
hardware floating is used.

     <br><dt><code>-mno-bit-align</code>
     <dd><dt><code>-mbit-align</code>
     <dd>On System V.4 and embedded PowerPC systems do not (do) force structures
and unions that contain bit-fields to be aligned to the base type of the
bit-field.

     <p>For example, by default a structure containing nothing but 8
<code>unsigned</code> bit-fields of length 1 would be aligned to a 4 byte
boundary and have a size of 4 bytes.  By using <code>-mno-bit-align</code>,
the structure would be aligned to a 1 byte boundary and be one byte in
size.

     <br><dt><code>-mno-strict-align</code>
     <dd><dt><code>-mstrict-align</code>
     <dd>On System V.4 and embedded PowerPC systems do not (do) assume that
unaligned memory references will be handled by the system.

     <br><dt><code>-mrelocatable</code>
     <dd><dt><code>-mno-relocatable</code>
     <dd>On embedded PowerPC systems generate code that allows (does not allow)
the program to be relocated to a different address at runtime.  If you
use <code>-mrelocatable</code> on any module, all objects linked together must
be compiled with <code>-mrelocatable</code> or <code>-mrelocatable-lib</code>.

     <br><dt><code>-mrelocatable-lib</code>
     <dd><dt><code>-mno-relocatable-lib</code>
     <dd>On embedded PowerPC systems generate code that allows (does not allow)
the program to be relocated to a different address at runtime.  Modules
compiled with <code>-mrelocatable-lib</code> can be linked with either modules
compiled without <code>-mrelocatable</code> and <code>-mrelocatable-lib</code> or
with modules compiled with the <code>-mrelocatable</code> options.

     <br><dt><code>-mno-toc</code>
     <dd><dt><code>-mtoc</code>
     <dd>On System V.4 and embedded PowerPC systems do not (do) assume that
register 2 contains a pointer to a global area pointing to the addresses
used in the program.

     <br><dt><code>-mlittle</code>
     <dd><dt><code>-mlittle-endian</code>
     <dd>On System V.4 and embedded PowerPC systems compile code for the
processor in little endian mode.  The <code>-mlittle-endian</code> option is
the same as <code>-mlittle</code>.

     <br><dt><code>-mbig</code>
     <dd><dt><code>-mbig-endian</code>
     <dd>On System V.4 and embedded PowerPC systems compile code for the
processor in big endian mode.  The <code>-mbig-endian</code> option is
the same as <code>-mbig</code>.

     <br><dt><code>-mcall-sysv</code>
     <dd>On System V.4 and embedded PowerPC systems compile code using calling
conventions that adheres to the March 1995 draft of the System V
Application Binary Interface, PowerPC processor supplement.  This is the
default unless you configured GCC using <code>powerpc-*-eabiaix</code>.

     <br><dt><code>-mcall-sysv-eabi</code>
     <dd>Specify both <code>-mcall-sysv</code> and <code>-meabi</code> options.

     <br><dt><code>-mcall-sysv-noeabi</code>
     <dd>Specify both <code>-mcall-sysv</code> and <code>-mno-eabi</code> options.

     <br><dt><code>-mcall-aix</code>
     <dd>On System V.4 and embedded PowerPC systems compile code using calling
conventions that are similar to those used on AIX.  This is the
default if you configured GCC using <code>powerpc-*-eabiaix</code>.

     <br><dt><code>-mcall-solaris</code>
     <dd>On System V.4 and embedded PowerPC systems compile code for the Solaris
operating system.

     <br><dt><code>-mcall-linux</code>
     <dd>On System V.4 and embedded PowerPC systems compile code for the
Linux-based GNU system.

     <br><dt><code>-mcall-gnu</code>
     <dd>On System V.4 and embedded PowerPC systems compile code for the
Hurd-based GNU system.

     <br><dt><code>-mcall-netbsd</code>
     <dd>On System V.4 and embedded PowerPC systems compile code for the
NetBSD operating system.

     <br><dt><code>-maix-struct-return</code>
     <dd>Return all structures in memory (as specified by the AIX ABI).

     <br><dt><code>-msvr4-struct-return</code>
     <dd>Return structures smaller than 8 bytes in registers (as specified by the
SVR4 ABI).

     <br><dt><code>-mabi=altivec</code>
     <dd>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.

     <br><dt><code>-mabi=no-altivec</code>
     <dd>Disable AltiVec ABI extensions for the current ABI.

     <br><dt><code>-mprototype</code>
     <dd><dt><code>-mno-prototype</code>
     <dd>On System V.4 and embedded PowerPC systems assume that all calls to
variable argument functions are properly prototyped.  Otherwise, the
compiler must insert an instruction before every non prototyped call to
set or clear bit 6 of the condition code register (<var>CR</var>) to
indicate whether floating point values were passed in the floating point
registers in case the function takes a variable arguments.  With
<code>-mprototype</code>, only calls to prototyped variable argument functions
will set or clear the bit.

     <br><dt><code>-msim</code>
     <dd>On embedded PowerPC systems, assume that the startup module is called
<code>sim-crt0.o</code> and that the standard C libraries are <code>libsim.a</code> and
<code>libc.a</code>.  This is the default for <code>powerpc-*-eabisim</code>. 
configurations.

     <br><dt><code>-mmvme</code>
     <dd>On embedded PowerPC systems, assume that the startup module is called
<code>crt0.o</code> and the standard C libraries are <code>libmvme.a</code> and
<code>libc.a</code>.

     <br><dt><code>-mads</code>
     <dd>On embedded PowerPC systems, assume that the startup module is called
<code>crt0.o</code> and the standard C libraries are <code>libads.a</code> and
<code>libc.a</code>.

     <br><dt><code>-myellowknife</code>
     <dd>On embedded PowerPC systems, assume that the startup module is called
<code>crt0.o</code> and the standard C libraries are <code>libyk.a</code> and
<code>libc.a</code>.

     <br><dt><code>-mvxworks</code>
     <dd>On System V.4 and embedded PowerPC systems, specify that you are
compiling for a VxWorks system.

     <br><dt><code>-mwindiss</code>
     <dd>Specify that you are compiling for the WindISS simulation environment.

     <br><dt><code>-memb</code>
     <dd>On embedded PowerPC systems, set the <var>PPC_EMB</var> bit in the ELF flags
header to indicate that <code>eabi</code> extended relocations are used.

     <br><dt><code>-meabi</code>
     <dd><dt><code>-mno-eabi</code>
     <dd>On System V.4 and embedded PowerPC systems do (do not) adhere to the
Embedded Applications Binary Interface (eabi) which is a set of
modifications to the System V.4 specifications.  Selecting <code>-meabi</code>
means that the stack is aligned to an 8 byte boundary, a function
<code>__eabi</code> is called to from <code>main</code> to set up the eabi
environment, and the <code>-msdata</code> option can use both <code>r2</code> and
<code>r13</code> to point to two separate small data areas.  Selecting
<code>-mno-eabi</code> means that the stack is aligned to a 16 byte boundary,
do not call an initialization function from <code>main</code>, and the
<code>-msdata</code> option will only use <code>r13</code> to point to a single
small data area.  The <code>-meabi</code> option is on by default if you
configured GCC using one of the <code>powerpc*-*-eabi*</code> options.

     <br><dt><code>-msdata=eabi</code>
     <dd>On System V.4 and embedded PowerPC systems, put small initialized
<code>const</code> global and static data in the <code>.sdata2</code> section, which
is pointed to by register <code>r2</code>.  Put small initialized
non-<code>const</code> global and static data in the <code>.sdata</code> section,
which is pointed to by register <code>r13</code>.  Put small uninitialized
global and static data in the <code>.sbss</code> section, which is adjacent to
the <code>.sdata</code> section.  The <code>-msdata=eabi</code> option is
incompatible with the <code>-mrelocatable</code> option.  The
<code>-msdata=eabi</code> option also sets the <code>-memb</code> option.

     <br><dt><code>-msdata=sysv</code>
     <dd>On System V.4 and embedded PowerPC systems, put small global and static
data in the <code>.sdata</code> section, which is pointed to by register
<code>r13</code>.  Put small uninitialized global and static data in the
<code>.sbss</code> section, which is adjacent to the <code>.sdata</code> section. 
The <code>-msdata=sysv</code> option is incompatible with the
<code>-mrelocatable</code> option.

     <br><dt><code>-msdata=default</code>
     <dd><dt><code>-msdata</code>
     <dd>On System V.4 and embedded PowerPC systems, if <code>-meabi</code> is used,
compile code the same as <code>-msdata=eabi</code>, otherwise compile code the
same as <code>-msdata=sysv</code>.

     <br><dt><code>-msdata-data</code>
     <dd>On System V.4 and embedded PowerPC systems, put small global and static
data in the <code>.sdata</code> section.  Put small uninitialized global and
static data in the <code>.sbss</code> section.  Do not use register <code>r13</code>
to address small data however.  This is the default behavior unless
other <code>-msdata</code> options are used.

     <br><dt><code>-msdata=none</code>
     <dd><dt><code>-mno-sdata</code>
     <dd>On embedded PowerPC systems, put all initialized global and static data
in the <code>.data</code> section, and all uninitialized data in the
<code>.bss</code> section.

     <br><dt><code>-G </code><var>num</var><code></code>
     <dd>On embedded PowerPC systems, put global and static items less than or
equal to <var>num</var> bytes into the small data or bss sections instead of
the normal data or bss section.  By default, <var>num</var> is 8.  The
<code>-G </code><var>num</var><code></code> switch is also passed to the linker. 
All modules should be compiled with the same <code>-G </code><var>num</var><code></code> value.

     <br><dt><code>-mregnames</code>
     <dd><dt><code>-mno-regnames</code>
     <dd>On System V.4 and embedded PowerPC systems do (do not) emit register
names in the assembly language output using symbolic forms.

     <br><dt><code>-mlongcall</code>
     <dd><dt><code>-mno-longcall</code>
     <dd>Default to making all function calls via pointers, so that functions
which reside further than 64 megabytes (67,108,864 bytes) from the
current location can be called.  This setting can be overridden by the
<code>shortcall</code> function attribute, or by <code>#pragma longcall(0)</code>.

     <p>Some linkers are capable of detecting out-of-range calls and generating
glue code on the fly.  On these systems, long calls are unnecessary and
generate slower code.  As of this writing, the AIX linker can do this,
as can the GNU linker for PowerPC/64.  It is planned to add this feature
to the GNU linker for 32-bit PowerPC systems as well.

     <p>In the future, we may cause GCC to ignore all longcall specifications
when the linker is known to generate glue.

     <br><dt><code>-pthread</code>
     <dd>Adds support for multithreading with the <dfn>pthreads</dfn> library. 
This option sets flags for both the preprocessor and linker.

   </dl>

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