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the monkey dances and laughs and sings and dances
4 years ago
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<title>RS/6000 and PowerPC Options - Using the GNU Compiler Collection (GCC)</title>
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<h4 class="subsection">3.17.37 IBM RS/6000 and PowerPC Options</h4>
<p><a name="index-RS_002f6000-and-PowerPC-Options-2199"></a><a name="index-IBM-RS_002f6000-and-PowerPC-Options-2200"></a>
These &lsquo;<samp><span class="samp">-m</span></samp>&rsquo; options are defined for the IBM RS/6000 and PowerPC:
<dl>
<dt><code>-mpowerpc-gpopt</code><dt><code>-mno-powerpc-gpopt</code><dt><code>-mpowerpc-gfxopt</code><dt><code>-mno-powerpc-gfxopt</code><dt><code>-mpowerpc64</code><dt><code>-mno-powerpc64</code><dt><code>-mmfcrf</code><dt><code>-mno-mfcrf</code><dt><code>-mpopcntb</code><dt><code>-mno-popcntb</code><dt><code>-mpopcntd</code><dt><code>-mno-popcntd</code><dt><code>-mfprnd</code><dt><code>-mno-fprnd</code><dt><code>-mcmpb</code><dt><code>-mno-cmpb</code><dt><code>-mmfpgpr</code><dt><code>-mno-mfpgpr</code><dt><code>-mhard-dfp</code><dt><code>-mno-hard-dfp</code><dd><a name="index-mpowerpc_002dgpopt-2201"></a><a name="index-mno_002dpowerpc_002dgpopt-2202"></a><a name="index-mpowerpc_002dgfxopt-2203"></a><a name="index-mno_002dpowerpc_002dgfxopt-2204"></a><a name="index-mpowerpc64-2205"></a><a name="index-mno_002dpowerpc64-2206"></a><a name="index-mmfcrf-2207"></a><a name="index-mno_002dmfcrf-2208"></a><a name="index-mpopcntb-2209"></a><a name="index-mno_002dpopcntb-2210"></a><a name="index-mpopcntd-2211"></a><a name="index-mno_002dpopcntd-2212"></a><a name="index-mfprnd-2213"></a><a name="index-mno_002dfprnd-2214"></a><a name="index-mcmpb-2215"></a><a name="index-mno_002dcmpb-2216"></a><a name="index-mmfpgpr-2217"></a><a name="index-mno_002dmfpgpr-2218"></a><a name="index-mhard_002ddfp-2219"></a><a name="index-mno_002dhard_002ddfp-2220"></a>You use these options to specify which instructions are available on the
processor you are using. The default value of these options is
determined when configuring GCC. Specifying the
<samp><span class="option">-mcpu=</span><var>cpu_type</var></samp> overrides the specification of these
options. We recommend you use the <samp><span class="option">-mcpu=</span><var>cpu_type</var></samp> option
rather than the options listed above.
<p>Specifying <samp><span class="option">-mpowerpc-gpopt</span></samp> allows
GCC to use the optional PowerPC architecture instructions in the
General Purpose group, including floating-point square root. Specifying
<samp><span class="option">-mpowerpc-gfxopt</span></samp> allows GCC to
use the optional PowerPC architecture instructions in the Graphics
group, including floating-point select.
<p>The <samp><span class="option">-mmfcrf</span></samp> option allows GCC to generate the move from
condition register field instruction implemented on the POWER4
processor and other processors that support the PowerPC V2.01
architecture.
The <samp><span class="option">-mpopcntb</span></samp> option allows GCC to generate the popcount and
double-precision FP reciprocal estimate instruction implemented on the
POWER5 processor and other processors that support the PowerPC V2.02
architecture.
The <samp><span class="option">-mpopcntd</span></samp> option allows GCC to generate the popcount
instruction implemented on the POWER7 processor and other processors
that support the PowerPC V2.06 architecture.
The <samp><span class="option">-mfprnd</span></samp> option allows GCC to generate the FP round to
integer instructions implemented on the POWER5+ processor and other
processors that support the PowerPC V2.03 architecture.
The <samp><span class="option">-mcmpb</span></samp> option allows GCC to generate the compare bytes
instruction implemented on the POWER6 processor and other processors
that support the PowerPC V2.05 architecture.
The <samp><span class="option">-mmfpgpr</span></samp> option allows GCC to generate the FP move to/from
general-purpose register instructions implemented on the POWER6X
processor and other processors that support the extended PowerPC V2.05
architecture.
The <samp><span class="option">-mhard-dfp</span></samp> option allows GCC to generate the decimal
floating-point instructions implemented on some POWER processors.
<p>The <samp><span class="option">-mpowerpc64</span></samp> option allows GCC to generate the additional
64-bit instructions that are found in the full PowerPC64 architecture
and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to
<samp><span class="option">-mno-powerpc64</span></samp>.
<br><dt><code>-mcpu=</code><var>cpu_type</var><dd><a name="index-mcpu-2221"></a>Set architecture type, register usage, and
instruction scheduling parameters for machine type <var>cpu_type</var>.
Supported values for <var>cpu_type</var> are &lsquo;<samp><span class="samp">401</span></samp>&rsquo;, &lsquo;<samp><span class="samp">403</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">405</span></samp>&rsquo;, &lsquo;<samp><span class="samp">405fp</span></samp>&rsquo;, &lsquo;<samp><span class="samp">440</span></samp>&rsquo;, &lsquo;<samp><span class="samp">440fp</span></samp>&rsquo;, &lsquo;<samp><span class="samp">464</span></samp>&rsquo;, &lsquo;<samp><span class="samp">464fp</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">476</span></samp>&rsquo;, &lsquo;<samp><span class="samp">476fp</span></samp>&rsquo;, &lsquo;<samp><span class="samp">505</span></samp>&rsquo;, &lsquo;<samp><span class="samp">601</span></samp>&rsquo;, &lsquo;<samp><span class="samp">602</span></samp>&rsquo;, &lsquo;<samp><span class="samp">603</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">603e</span></samp>&rsquo;, &lsquo;<samp><span class="samp">604</span></samp>&rsquo;, &lsquo;<samp><span class="samp">604e</span></samp>&rsquo;, &lsquo;<samp><span class="samp">620</span></samp>&rsquo;, &lsquo;<samp><span class="samp">630</span></samp>&rsquo;, &lsquo;<samp><span class="samp">740</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">7400</span></samp>&rsquo;, &lsquo;<samp><span class="samp">7450</span></samp>&rsquo;, &lsquo;<samp><span class="samp">750</span></samp>&rsquo;, &lsquo;<samp><span class="samp">801</span></samp>&rsquo;, &lsquo;<samp><span class="samp">821</span></samp>&rsquo;, &lsquo;<samp><span class="samp">823</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">860</span></samp>&rsquo;, &lsquo;<samp><span class="samp">970</span></samp>&rsquo;, &lsquo;<samp><span class="samp">8540</span></samp>&rsquo;, &lsquo;<samp><span class="samp">a2</span></samp>&rsquo;, &lsquo;<samp><span class="samp">e300c2</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">e300c3</span></samp>&rsquo;, &lsquo;<samp><span class="samp">e500mc</span></samp>&rsquo;, &lsquo;<samp><span class="samp">e500mc64</span></samp>&rsquo;, &lsquo;<samp><span class="samp">e5500</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">e6500</span></samp>&rsquo;, &lsquo;<samp><span class="samp">ec603e</span></samp>&rsquo;, &lsquo;<samp><span class="samp">G3</span></samp>&rsquo;, &lsquo;<samp><span class="samp">G4</span></samp>&rsquo;, &lsquo;<samp><span class="samp">G5</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">titan</span></samp>&rsquo;, &lsquo;<samp><span class="samp">power3</span></samp>&rsquo;, &lsquo;<samp><span class="samp">power4</span></samp>&rsquo;, &lsquo;<samp><span class="samp">power5</span></samp>&rsquo;, &lsquo;<samp><span class="samp">power5+</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">power6</span></samp>&rsquo;, &lsquo;<samp><span class="samp">power6x</span></samp>&rsquo;, &lsquo;<samp><span class="samp">power7</span></samp>&rsquo;, &lsquo;<samp><span class="samp">power8</span></samp>&rsquo;, &lsquo;<samp><span class="samp">powerpc</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">powerpc64</span></samp>&rsquo;, &lsquo;<samp><span class="samp">powerpc64le</span></samp>&rsquo;, and &lsquo;<samp><span class="samp">rs64</span></samp>&rsquo;.
<p><samp><span class="option">-mcpu=powerpc</span></samp>, <samp><span class="option">-mcpu=powerpc64</span></samp>, and
<samp><span class="option">-mcpu=powerpc64le</span></samp> specify pure 32-bit PowerPC (either
endian), 64-bit big endian PowerPC and 64-bit little endian PowerPC
architecture machine types, with an appropriate, generic processor
model assumed for scheduling purposes.
<p>The other options specify a specific processor. Code generated under
those options runs best on that processor, and may not run at all on
others.
<p>The <samp><span class="option">-mcpu</span></samp> options automatically enable or disable the
following options:
<pre class="smallexample"> -maltivec -mfprnd -mhard-float -mmfcrf -mmultiple
-mpopcntb -mpopcntd -mpowerpc64
-mpowerpc-gpopt -mpowerpc-gfxopt -msingle-float -mdouble-float
-msimple-fpu -mstring -mmulhw -mdlmzb -mmfpgpr -mvsx
-mcrypto -mdirect-move -mpower8-fusion -mpower8-vector
-mquad-memory -mquad-memory-atomic
</pre>
<p>The particular options set for any particular CPU varies between
compiler versions, depending on what setting seems to produce optimal
code for that CPU; it doesn't necessarily reflect the actual hardware's
capabilities. If you wish to set an individual option to a particular
value, you may specify it after the <samp><span class="option">-mcpu</span></samp> option, like
<samp><span class="option">-mcpu=970 -mno-altivec</span></samp>.
<p>On AIX, the <samp><span class="option">-maltivec</span></samp> and <samp><span class="option">-mpowerpc64</span></samp> options are
not enabled or disabled by the <samp><span class="option">-mcpu</span></samp> option at present because
AIX does not have full support for these options. You may still
enable or disable them individually if you're sure it'll work in your
environment.
<br><dt><code>-mtune=</code><var>cpu_type</var><dd><a name="index-mtune-2222"></a>Set the instruction scheduling parameters for machine type
<var>cpu_type</var>, but do not set the architecture type or register usage,
as <samp><span class="option">-mcpu=</span><var>cpu_type</var></samp> does. The same
values for <var>cpu_type</var> are used for <samp><span class="option">-mtune</span></samp> as for
<samp><span class="option">-mcpu</span></samp>. If both are specified, the code generated uses the
architecture and registers set by <samp><span class="option">-mcpu</span></samp>, but the
scheduling parameters set by <samp><span class="option">-mtune</span></samp>.
<br><dt><code>-mcmodel=small</code><dd><a name="index-mcmodel_003dsmall-2223"></a>Generate PowerPC64 code for the small model: The TOC is limited to
64k.
<br><dt><code>-mcmodel=medium</code><dd><a name="index-mcmodel_003dmedium-2224"></a>Generate PowerPC64 code for the medium model: The TOC and other static
data may be up to a total of 4G in size.
<br><dt><code>-mcmodel=large</code><dd><a name="index-mcmodel_003dlarge-2225"></a>Generate PowerPC64 code for the large model: The TOC may be up to 4G
in size. Other data and code is only limited by the 64-bit address
space.
<br><dt><code>-maltivec</code><dt><code>-mno-altivec</code><dd><a name="index-maltivec-2226"></a><a name="index-mno_002daltivec-2227"></a>Generate code that uses (does not use) AltiVec instructions, and also
enable the use of built-in functions that allow more direct access to
the AltiVec instruction set. You may also need to set
<samp><span class="option">-mabi=altivec</span></samp> to adjust the current ABI with AltiVec ABI
enhancements.
<p>When <samp><span class="option">-maltivec</span></samp> is used, rather than <samp><span class="option">-maltivec=le</span></samp> or
<samp><span class="option">-maltivec=be</span></samp>, the element order for Altivec intrinsics such
as <code>vec_splat</code>, <code>vec_extract</code>, and <code>vec_insert</code>
match array element order corresponding to the endianness of the
target. That is, element zero identifies the leftmost element in a
vector register when targeting a big-endian platform, and identifies
the rightmost element in a vector register when targeting a
little-endian platform.
<br><dt><code>-maltivec=be</code><dd><a name="index-maltivec_003dbe-2228"></a>Generate Altivec instructions using big-endian element order,
regardless of whether the target is big- or little-endian. This is
the default when targeting a big-endian platform.
<p>The element order is used to interpret element numbers in Altivec
intrinsics such as <code>vec_splat</code>, <code>vec_extract</code>, and
<code>vec_insert</code>. By default, these match array element order
corresponding to the endianness for the target.
<br><dt><code>-maltivec=le</code><dd><a name="index-maltivec_003dle-2229"></a>Generate Altivec instructions using little-endian element order,
regardless of whether the target is big- or little-endian. This is
the default when targeting a little-endian platform. This option is
currently ignored when targeting a big-endian platform.
<p>The element order is used to interpret element numbers in Altivec
intrinsics such as <code>vec_splat</code>, <code>vec_extract</code>, and
<code>vec_insert</code>. By default, these match array element order
corresponding to the endianness for the target.
<br><dt><code>-mvrsave</code><dt><code>-mno-vrsave</code><dd><a name="index-mvrsave-2230"></a><a name="index-mno_002dvrsave-2231"></a>Generate VRSAVE instructions when generating AltiVec code.
<br><dt><code>-mgen-cell-microcode</code><dd><a name="index-mgen_002dcell_002dmicrocode-2232"></a>Generate Cell microcode instructions.
<br><dt><code>-mwarn-cell-microcode</code><dd><a name="index-mwarn_002dcell_002dmicrocode-2233"></a>Warn when a Cell microcode instruction is emitted. An example
of a Cell microcode instruction is a variable shift.
<br><dt><code>-msecure-plt</code><dd><a name="index-msecure_002dplt-2234"></a>Generate code that allows <samp><span class="command">ld</span></samp> and <samp><span class="command">ld.so</span></samp>
to build executables and shared
libraries with non-executable <code>.plt</code> and <code>.got</code> sections.
This is a PowerPC
32-bit SYSV ABI option.
<br><dt><code>-mbss-plt</code><dd><a name="index-mbss_002dplt-2235"></a>Generate code that uses a BSS <code>.plt</code> section that <samp><span class="command">ld.so</span></samp>
fills in, and
requires <code>.plt</code> and <code>.got</code>
sections that are both writable and executable.
This is a PowerPC 32-bit SYSV ABI option.
<br><dt><code>-misel</code><dt><code>-mno-isel</code><dd><a name="index-misel-2236"></a><a name="index-mno_002disel-2237"></a>This switch enables or disables the generation of ISEL instructions.
<br><dt><code>-misel=</code><var>yes/no</var><dd>This switch has been deprecated. Use <samp><span class="option">-misel</span></samp> and
<samp><span class="option">-mno-isel</span></samp> instead.
<br><dt><code>-mspe</code><dt><code>-mno-spe</code><dd><a name="index-mspe-2238"></a><a name="index-mno_002dspe-2239"></a>This switch enables or disables the generation of SPE simd
instructions.
<br><dt><code>-mpaired</code><dt><code>-mno-paired</code><dd><a name="index-mpaired-2240"></a><a name="index-mno_002dpaired-2241"></a>This switch enables or disables the generation of PAIRED simd
instructions.
<br><dt><code>-mspe=</code><var>yes/no</var><dd>This option has been deprecated. Use <samp><span class="option">-mspe</span></samp> and
<samp><span class="option">-mno-spe</span></samp> instead.
<br><dt><code>-mvsx</code><dt><code>-mno-vsx</code><dd><a name="index-mvsx-2242"></a><a name="index-mno_002dvsx-2243"></a>Generate code that uses (does not use) vector/scalar (VSX)
instructions, and also enable the use of built-in functions that allow
more direct access to the VSX instruction set.
<br><dt><code>-mcrypto</code><dt><code>-mno-crypto</code><dd><a name="index-mcrypto-2244"></a><a name="index-mno_002dcrypto-2245"></a>Enable the use (disable) of the built-in functions that allow direct
access to the cryptographic instructions that were added in version
2.07 of the PowerPC ISA.
<br><dt><code>-mdirect-move</code><dt><code>-mno-direct-move</code><dd><a name="index-mdirect_002dmove-2246"></a><a name="index-mno_002ddirect_002dmove-2247"></a>Generate code that uses (does not use) the instructions to move data
between the general purpose registers and the vector/scalar (VSX)
registers that were added in version 2.07 of the PowerPC ISA.
<br><dt><code>-mpower8-fusion</code><dt><code>-mno-power8-fusion</code><dd><a name="index-mpower8_002dfusion-2248"></a><a name="index-mno_002dpower8_002dfusion-2249"></a>Generate code that keeps (does not keeps) some integer operations
adjacent so that the instructions can be fused together on power8 and
later processors.
<br><dt><code>-mpower8-vector</code><dt><code>-mno-power8-vector</code><dd><a name="index-mpower8_002dvector-2250"></a><a name="index-mno_002dpower8_002dvector-2251"></a>Generate code that uses (does not use) the vector and scalar
instructions that were added in version 2.07 of the PowerPC ISA. Also
enable the use of built-in functions that allow more direct access to
the vector instructions.
<br><dt><code>-mquad-memory</code><dt><code>-mno-quad-memory</code><dd><a name="index-mquad_002dmemory-2252"></a><a name="index-mno_002dquad_002dmemory-2253"></a>Generate code that uses (does not use) the non-atomic quad word memory
instructions. The <samp><span class="option">-mquad-memory</span></samp> option requires use of
64-bit mode.
<br><dt><code>-mquad-memory-atomic</code><dt><code>-mno-quad-memory-atomic</code><dd><a name="index-mquad_002dmemory_002datomic-2254"></a><a name="index-mno_002dquad_002dmemory_002datomic-2255"></a>Generate code that uses (does not use) the atomic quad word memory
instructions. The <samp><span class="option">-mquad-memory-atomic</span></samp> option requires use of
64-bit mode.
<br><dt><code>-mupper-regs-df</code><dt><code>-mno-upper-regs-df</code><dd><a name="index-mupper_002dregs_002ddf-2256"></a><a name="index-mno_002dupper_002dregs_002ddf-2257"></a>Generate code that uses (does not use) the scalar double precision
instructions that target all 64 registers in the vector/scalar
floating point register set that were added in version 2.06 of the
PowerPC ISA. <samp><span class="option">-mupper-regs-df</span></samp> is turned on by default if you
use any of the <samp><span class="option">-mcpu=power7</span></samp>, <samp><span class="option">-mcpu=power8</span></samp>, or
<samp><span class="option">-mvsx</span></samp> options.
<br><dt><code>-mupper-regs-sf</code><dt><code>-mno-upper-regs-sf</code><dd><a name="index-mupper_002dregs_002dsf-2258"></a><a name="index-mno_002dupper_002dregs_002dsf-2259"></a>Generate code that uses (does not use) the scalar single precision
instructions that target all 64 registers in the vector/scalar
floating point register set that were added in version 2.07 of the
PowerPC ISA. <samp><span class="option">-mupper-regs-sf</span></samp> is turned on by default if you
use either of the <samp><span class="option">-mcpu=power8</span></samp> or <samp><span class="option">-mpower8-vector</span></samp>
options.
<br><dt><code>-mupper-regs</code><dt><code>-mno-upper-regs</code><dd><a name="index-mupper_002dregs-2260"></a><a name="index-mno_002dupper_002dregs-2261"></a>Generate code that uses (does not use) the scalar
instructions that target all 64 registers in the vector/scalar
floating point register set, depending on the model of the machine.
<p>If the <samp><span class="option">-mno-upper-regs</span></samp> option is used, it turns off both
<samp><span class="option">-mupper-regs-sf</span></samp> and <samp><span class="option">-mupper-regs-df</span></samp> options.
<br><dt><code>-mfloat-gprs=</code><var>yes/single/double/no</var><dt><code>-mfloat-gprs</code><dd><a name="index-mfloat_002dgprs-2262"></a>This switch enables or disables the generation of floating-point
operations on the general-purpose registers for architectures that
support it.
<p>The argument &lsquo;<samp><span class="samp">yes</span></samp>&rsquo; or &lsquo;<samp><span class="samp">single</span></samp>&rsquo; enables the use of
single-precision floating-point operations.
<p>The argument &lsquo;<samp><span class="samp">double</span></samp>&rsquo; enables the use of single and
double-precision floating-point operations.
<p>The argument &lsquo;<samp><span class="samp">no</span></samp>&rsquo; disables floating-point operations on the
general-purpose registers.
<p>This option is currently only available on the MPC854x.
<br><dt><code>-m32</code><dt><code>-m64</code><dd><a name="index-m32-2263"></a><a name="index-m64-2264"></a>Generate code for 32-bit or 64-bit environments of Darwin and SVR4
targets (including GNU/Linux). The 32-bit environment sets int, long
and pointer to 32 bits and generates code that runs on any PowerPC
variant. The 64-bit environment sets int to 32 bits and long and
pointer to 64 bits, and generates code for PowerPC64, as for
<samp><span class="option">-mpowerpc64</span></samp>.
<br><dt><code>-mfull-toc</code><dt><code>-mno-fp-in-toc</code><dt><code>-mno-sum-in-toc</code><dt><code>-mminimal-toc</code><dd><a name="index-mfull_002dtoc-2265"></a><a name="index-mno_002dfp_002din_002dtoc-2266"></a><a name="index-mno_002dsum_002din_002dtoc-2267"></a><a name="index-mminimal_002dtoc-2268"></a>Modify generation of the TOC (Table Of Contents), which is created for
every executable file. The <samp><span class="option">-mfull-toc</span></samp> option is selected by
default. In that case, GCC allocates at least one TOC entry for
each unique non-automatic variable reference in your program. GCC
also places floating-point constants in the TOC. However, only
16,384 entries are available in the TOC.
<p>If you receive a linker error message that saying you have overflowed
the available TOC space, you can reduce the amount of TOC space used
with the <samp><span class="option">-mno-fp-in-toc</span></samp> and <samp><span class="option">-mno-sum-in-toc</span></samp> options.
<samp><span class="option">-mno-fp-in-toc</span></samp> prevents GCC from putting floating-point
constants in the TOC and <samp><span class="option">-mno-sum-in-toc</span></samp> forces GCC to
generate code to calculate the sum of an address and a constant at
run time instead of putting that sum into the TOC. You may specify one
or both of these options. Each causes GCC to produce very slightly
slower and larger code at the expense of conserving TOC space.
<p>If you still run out of space in the TOC even when you specify both of
these options, specify <samp><span class="option">-mminimal-toc</span></samp> instead. This option causes
GCC to make only one TOC entry for every file. When you specify this
option, GCC produces code that is slower and larger but which
uses extremely little TOC space. You may wish to use this option
only on files that contain less frequently-executed code.
<br><dt><code>-maix64</code><dt><code>-maix32</code><dd><a name="index-maix64-2269"></a><a name="index-maix32-2270"></a>Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit
<code>long</code> type, and the infrastructure needed to support them.
Specifying <samp><span class="option">-maix64</span></samp> implies <samp><span class="option">-mpowerpc64</span></samp>,
while <samp><span class="option">-maix32</span></samp> disables the 64-bit ABI and
implies <samp><span class="option">-mno-powerpc64</span></samp>. GCC defaults to <samp><span class="option">-maix32</span></samp>.
<br><dt><code>-mxl-compat</code><dt><code>-mno-xl-compat</code><dd><a name="index-mxl_002dcompat-2271"></a><a name="index-mno_002dxl_002dcompat-2272"></a>Produce code that conforms more closely to IBM XL compiler semantics
when using AIX-compatible ABI. Pass floating-point arguments to
prototyped functions beyond the register save area (RSA) on the stack
in addition to argument FPRs. Do not assume that most significant
double in 128-bit long double value is properly rounded when comparing
values and converting to double. Use XL symbol names for long double
support routines.
<p>The AIX calling convention was extended but not initially documented to
handle an obscure K&amp;R C case of calling a function that takes the
address of its arguments with fewer arguments than declared. IBM XL
compilers access floating-point arguments that do not fit in the
RSA from the stack when a subroutine is compiled without
optimization. Because always storing floating-point arguments on the
stack is inefficient and rarely needed, this option is not enabled by
default and only is necessary when calling subroutines compiled by IBM
XL compilers without optimization.
<br><dt><code>-mpe</code><dd><a name="index-mpe-2273"></a>Support <dfn>IBM RS/6000 SP</dfn> <dfn>Parallel Environment</dfn> (PE). Link an
application written to use message passing with special startup code to
enable the application to run. The system must have PE installed in the
standard location (<samp><span class="file">/usr/lpp/ppe.poe/</span></samp>), or the <samp><span class="file">specs</span></samp> file
must be overridden with the <samp><span class="option">-specs=</span></samp> option to specify the
appropriate directory location. The Parallel Environment does not
support threads, so the <samp><span class="option">-mpe</span></samp> option and the <samp><span class="option">-pthread</span></samp>
option are incompatible.
<br><dt><code>-malign-natural</code><dt><code>-malign-power</code><dd><a name="index-malign_002dnatural-2274"></a><a name="index-malign_002dpower-2275"></a>On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option
<samp><span class="option">-malign-natural</span></samp> overrides the ABI-defined alignment of larger
types, such as floating-point doubles, on their natural size-based boundary.
The option <samp><span class="option">-malign-power</span></samp> instructs GCC to follow the ABI-specified
alignment rules. GCC defaults to the standard alignment defined in the ABI.
<p>On 64-bit Darwin, natural alignment is the default, and <samp><span class="option">-malign-power</span></samp>
is not supported.
<br><dt><code>-msoft-float</code><dt><code>-mhard-float</code><dd><a name="index-msoft_002dfloat-2276"></a><a name="index-mhard_002dfloat-2277"></a>Generate code that does not use (uses) the floating-point register set.
Software floating-point emulation is provided if you use the
<samp><span class="option">-msoft-float</span></samp> option, and pass the option to GCC when linking.
<br><dt><code>-msingle-float</code><dt><code>-mdouble-float</code><dd><a name="index-msingle_002dfloat-2278"></a><a name="index-mdouble_002dfloat-2279"></a>Generate code for single- or double-precision floating-point operations.
<samp><span class="option">-mdouble-float</span></samp> implies <samp><span class="option">-msingle-float</span></samp>.
<br><dt><code>-msimple-fpu</code><dd><a name="index-msimple_002dfpu-2280"></a>Do not generate <code>sqrt</code> and <code>div</code> instructions for hardware
floating-point unit.
<br><dt><code>-mfpu=</code><var>name</var><dd><a name="index-mfpu-2281"></a>Specify type of floating-point unit. Valid values for <var>name</var> are
&lsquo;<samp><span class="samp">sp_lite</span></samp>&rsquo; (equivalent to <samp><span class="option">-msingle-float -msimple-fpu</span></samp>),
&lsquo;<samp><span class="samp">dp_lite</span></samp>&rsquo; (equivalent to <samp><span class="option">-mdouble-float -msimple-fpu</span></samp>),
&lsquo;<samp><span class="samp">sp_full</span></samp>&rsquo; (equivalent to <samp><span class="option">-msingle-float</span></samp>),
and &lsquo;<samp><span class="samp">dp_full</span></samp>&rsquo; (equivalent to <samp><span class="option">-mdouble-float</span></samp>).
<br><dt><code>-mxilinx-fpu</code><dd><a name="index-mxilinx_002dfpu-2282"></a>Perform optimizations for the floating-point unit on Xilinx PPC 405/440.
<br><dt><code>-mmultiple</code><dt><code>-mno-multiple</code><dd><a name="index-mmultiple-2283"></a><a name="index-mno_002dmultiple-2284"></a>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 <samp><span class="option">-mmultiple</span></samp> on little-endian
PowerPC systems, since those instructions do not work when the
processor is in little-endian mode. The exceptions are PPC740 and
PPC750 which permit these instructions in little-endian mode.
<br><dt><code>-mstring</code><dt><code>-mno-string</code><dd><a name="index-mstring-2285"></a><a name="index-mno_002dstring-2286"></a>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
<samp><span class="option">-mstring</span></samp> on little-endian PowerPC systems, since those
instructions do not work when the processor is in little-endian mode.
The exceptions are PPC740 and PPC750 which permit these instructions
in little-endian mode.
<br><dt><code>-mupdate</code><dt><code>-mno-update</code><dd><a name="index-mupdate-2287"></a><a name="index-mno_002dupdate-2288"></a>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
<samp><span class="option">-mno-update</span></samp>, 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>-mavoid-indexed-addresses</code><dt><code>-mno-avoid-indexed-addresses</code><dd><a name="index-mavoid_002dindexed_002daddresses-2289"></a><a name="index-mno_002davoid_002dindexed_002daddresses-2290"></a>Generate code that tries to avoid (not avoid) the use of indexed load
or store instructions. These instructions can incur a performance
penalty on Power6 processors in certain situations, such as when
stepping through large arrays that cross a 16M boundary. This option
is enabled by default when targeting Power6 and disabled otherwise.
<br><dt><code>-mfused-madd</code><dt><code>-mno-fused-madd</code><dd><a name="index-mfused_002dmadd-2291"></a><a name="index-mno_002dfused_002dmadd-2292"></a>Generate code that uses (does not use) the floating-point multiply and
accumulate instructions. These instructions are generated by default
if hardware floating point is used. The machine-dependent
<samp><span class="option">-mfused-madd</span></samp> option is now mapped to the machine-independent
<samp><span class="option">-ffp-contract=fast</span></samp> option, and <samp><span class="option">-mno-fused-madd</span></samp> is
mapped to <samp><span class="option">-ffp-contract=off</span></samp>.
<br><dt><code>-mmulhw</code><dt><code>-mno-mulhw</code><dd><a name="index-mmulhw-2293"></a><a name="index-mno_002dmulhw-2294"></a>Generate code that uses (does not use) the half-word multiply and
multiply-accumulate instructions on the IBM 405, 440, 464 and 476 processors.
These instructions are generated by default when targeting those
processors.
<br><dt><code>-mdlmzb</code><dt><code>-mno-dlmzb</code><dd><a name="index-mdlmzb-2295"></a><a name="index-mno_002ddlmzb-2296"></a>Generate code that uses (does not use) the string-search &lsquo;<samp><span class="samp">dlmzb</span></samp>&rsquo;
instruction on the IBM 405, 440, 464 and 476 processors. This instruction is
generated by default when targeting those processors.
<br><dt><code>-mno-bit-align</code><dt><code>-mbit-align</code><dd><a name="index-mno_002dbit_002dalign-2297"></a><a name="index-mbit_002dalign-2298"></a>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 is aligned to a 4-byte
boundary and has a size of 4 bytes. By using <samp><span class="option">-mno-bit-align</span></samp>,
the structure is aligned to a 1-byte boundary and is 1 byte in
size.
<br><dt><code>-mno-strict-align</code><dt><code>-mstrict-align</code><dd><a name="index-mno_002dstrict_002dalign-2299"></a><a name="index-mstrict_002dalign-2300"></a>On System V.4 and embedded PowerPC systems do not (do) assume that
unaligned memory references are handled by the system.
<br><dt><code>-mrelocatable</code><dt><code>-mno-relocatable</code><dd><a name="index-mrelocatable-2301"></a><a name="index-mno_002drelocatable-2302"></a>Generate code that allows (does not allow) a static executable to be
relocated to a different address at run time. A simple embedded
PowerPC system loader should relocate the entire contents of
<code>.got2</code> and 4-byte locations listed in the <code>.fixup</code> section,
a table of 32-bit addresses generated by this option. For this to
work, all objects linked together must be compiled with
<samp><span class="option">-mrelocatable</span></samp> or <samp><span class="option">-mrelocatable-lib</span></samp>.
<samp><span class="option">-mrelocatable</span></samp> code aligns the stack to an 8-byte boundary.
<br><dt><code>-mrelocatable-lib</code><dt><code>-mno-relocatable-lib</code><dd><a name="index-mrelocatable_002dlib-2303"></a><a name="index-mno_002drelocatable_002dlib-2304"></a>Like <samp><span class="option">-mrelocatable</span></samp>, <samp><span class="option">-mrelocatable-lib</span></samp> generates a
<code>.fixup</code> section to allow static executables to be relocated at
run time, but <samp><span class="option">-mrelocatable-lib</span></samp> does not use the smaller stack
alignment of <samp><span class="option">-mrelocatable</span></samp>. Objects compiled with
<samp><span class="option">-mrelocatable-lib</span></samp> may be linked with objects compiled with
any combination of the <samp><span class="option">-mrelocatable</span></samp> options.
<br><dt><code>-mno-toc</code><dt><code>-mtoc</code><dd><a name="index-mno_002dtoc-2305"></a><a name="index-mtoc-2306"></a>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><dt><code>-mlittle-endian</code><dd><a name="index-mlittle-2307"></a><a name="index-mlittle_002dendian-2308"></a>On System V.4 and embedded PowerPC systems compile code for the
processor in little-endian mode. The <samp><span class="option">-mlittle-endian</span></samp> option is
the same as <samp><span class="option">-mlittle</span></samp>.
<br><dt><code>-mbig</code><dt><code>-mbig-endian</code><dd><a name="index-mbig-2309"></a><a name="index-mbig_002dendian-2310"></a>On System V.4 and embedded PowerPC systems compile code for the
processor in big-endian mode. The <samp><span class="option">-mbig-endian</span></samp> option is
the same as <samp><span class="option">-mbig</span></samp>.
<br><dt><code>-mdynamic-no-pic</code><dd><a name="index-mdynamic_002dno_002dpic-2311"></a>On Darwin and Mac OS X systems, compile code so that it is not
relocatable, but that its external references are relocatable. The
resulting code is suitable for applications, but not shared
libraries.
<br><dt><code>-msingle-pic-base</code><dd><a name="index-msingle_002dpic_002dbase-2312"></a>Treat the register used for PIC addressing as read-only, rather than
loading it in the prologue for each function. The runtime system is
responsible for initializing this register with an appropriate value
before execution begins.
<br><dt><code>-mprioritize-restricted-insns=</code><var>priority</var><dd><a name="index-mprioritize_002drestricted_002dinsns-2313"></a>This option controls the priority that is assigned to
dispatch-slot restricted instructions during the second scheduling
pass. The argument <var>priority</var> takes the value &lsquo;<samp><span class="samp">0</span></samp>&rsquo;, &lsquo;<samp><span class="samp">1</span></samp>&rsquo;,
or &lsquo;<samp><span class="samp">2</span></samp>&rsquo; to assign no, highest, or second-highest (respectively)
priority to dispatch-slot restricted
instructions.
<br><dt><code>-msched-costly-dep=</code><var>dependence_type</var><dd><a name="index-msched_002dcostly_002ddep-2314"></a>This option controls which dependences are considered costly
by the target during instruction scheduling. The argument
<var>dependence_type</var> takes one of the following values:
<dl>
<dt>&lsquo;<samp><span class="samp">no</span></samp>&rsquo;<dd>No dependence is costly.
<br><dt>&lsquo;<samp><span class="samp">all</span></samp>&rsquo;<dd>All dependences are costly.
<br><dt>&lsquo;<samp><span class="samp">true_store_to_load</span></samp>&rsquo;<dd>A true dependence from store to load is costly.
<br><dt>&lsquo;<samp><span class="samp">store_to_load</span></samp>&rsquo;<dd>Any dependence from store to load is costly.
<br><dt><var>number</var><dd>Any dependence for which the latency is greater than or equal to
<var>number</var> is costly.
</dl>
<br><dt><code>-minsert-sched-nops=</code><var>scheme</var><dd><a name="index-minsert_002dsched_002dnops-2315"></a>This option controls which NOP insertion scheme is used during
the second scheduling pass. The argument <var>scheme</var> takes one of the
following values:
<dl>
<dt>&lsquo;<samp><span class="samp">no</span></samp>&rsquo;<dd>Don't insert NOPs.
<br><dt>&lsquo;<samp><span class="samp">pad</span></samp>&rsquo;<dd>Pad with NOPs any dispatch group that has vacant issue slots,
according to the scheduler's grouping.
<br><dt>&lsquo;<samp><span class="samp">regroup_exact</span></samp>&rsquo;<dd>Insert NOPs to force costly dependent insns into
separate groups. Insert exactly as many NOPs as needed to force an insn
to a new group, according to the estimated processor grouping.
<br><dt><var>number</var><dd>Insert NOPs to force costly dependent insns into
separate groups. Insert <var>number</var> NOPs to force an insn to a new group.
</dl>
<br><dt><code>-mcall-sysv</code><dd><a name="index-mcall_002dsysv-2316"></a>On System V.4 and embedded PowerPC systems compile code using calling
conventions that adhere to the March 1995 draft of the System V
Application Binary Interface, PowerPC processor supplement. This is the
default unless you configured GCC using &lsquo;<samp><span class="samp">powerpc-*-eabiaix</span></samp>&rsquo;.
<br><dt><code>-mcall-sysv-eabi</code><dt><code>-mcall-eabi</code><dd><a name="index-mcall_002dsysv_002deabi-2317"></a><a name="index-mcall_002deabi-2318"></a>Specify both <samp><span class="option">-mcall-sysv</span></samp> and <samp><span class="option">-meabi</span></samp> options.
<br><dt><code>-mcall-sysv-noeabi</code><dd><a name="index-mcall_002dsysv_002dnoeabi-2319"></a>Specify both <samp><span class="option">-mcall-sysv</span></samp> and <samp><span class="option">-mno-eabi</span></samp> options.
<br><dt><code>-mcall-aixdesc</code><dd><a name="index-m-2320"></a>On System V.4 and embedded PowerPC systems compile code for the AIX
operating system.
<br><dt><code>-mcall-linux</code><dd><a name="index-mcall_002dlinux-2321"></a>On System V.4 and embedded PowerPC systems compile code for the
Linux-based GNU system.
<br><dt><code>-mcall-freebsd</code><dd><a name="index-mcall_002dfreebsd-2322"></a>On System V.4 and embedded PowerPC systems compile code for the
FreeBSD operating system.
<br><dt><code>-mcall-netbsd</code><dd><a name="index-mcall_002dnetbsd-2323"></a>On System V.4 and embedded PowerPC systems compile code for the
NetBSD operating system.
<br><dt><code>-mcall-openbsd</code><dd><a name="index-mcall_002dnetbsd-2324"></a>On System V.4 and embedded PowerPC systems compile code for the
OpenBSD operating system.
<br><dt><code>-maix-struct-return</code><dd><a name="index-maix_002dstruct_002dreturn-2325"></a>Return all structures in memory (as specified by the AIX ABI).
<br><dt><code>-msvr4-struct-return</code><dd><a name="index-msvr4_002dstruct_002dreturn-2326"></a>Return structures smaller than 8 bytes in registers (as specified by the
SVR4 ABI).
<br><dt><code>-mabi=</code><var>abi-type</var><dd><a name="index-mabi-2327"></a>Extend the current ABI with a particular extension, or remove such extension.
Valid values are &lsquo;<samp><span class="samp">altivec</span></samp>&rsquo;, &lsquo;<samp><span class="samp">no-altivec</span></samp>&rsquo;, &lsquo;<samp><span class="samp">spe</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">no-spe</span></samp>&rsquo;, &lsquo;<samp><span class="samp">ibmlongdouble</span></samp>&rsquo;, &lsquo;<samp><span class="samp">ieeelongdouble</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">elfv1</span></samp>&rsquo;, &lsquo;<samp><span class="samp">elfv2</span></samp>&rsquo;.
<br><dt><code>-mabi=spe</code><dd><a name="index-mabi_003dspe-2328"></a>Extend the current ABI with SPE ABI extensions. This does not change
the default ABI, instead it adds the SPE ABI extensions to the current
ABI.
<br><dt><code>-mabi=no-spe</code><dd><a name="index-mabi_003dno_002dspe-2329"></a>Disable Book-E SPE ABI extensions for the current ABI.
<br><dt><code>-mabi=ibmlongdouble</code><dd><a name="index-mabi_003dibmlongdouble-2330"></a>Change the current ABI to use IBM extended-precision long double.
This is a PowerPC 32-bit SYSV ABI option.
<br><dt><code>-mabi=ieeelongdouble</code><dd><a name="index-mabi_003dieeelongdouble-2331"></a>Change the current ABI to use IEEE extended-precision long double.
This is a PowerPC 32-bit Linux ABI option.
<br><dt><code>-mabi=elfv1</code><dd><a name="index-mabi_003delfv1-2332"></a>Change the current ABI to use the ELFv1 ABI.
This is the default ABI for big-endian PowerPC 64-bit Linux.
Overriding the default ABI requires special system support and is
likely to fail in spectacular ways.
<br><dt><code>-mabi=elfv2</code><dd><a name="index-mabi_003delfv2-2333"></a>Change the current ABI to use the ELFv2 ABI.
This is the default ABI for little-endian PowerPC 64-bit Linux.
Overriding the default ABI requires special system support and is
likely to fail in spectacular ways.
<br><dt><code>-mprototype</code><dt><code>-mno-prototype</code><dd><a name="index-mprototype-2334"></a><a name="index-mno_002dprototype-2335"></a>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 (<code>CR</code>) to
indicate whether floating-point values are passed in the floating-point
registers in case the function takes variable arguments. With
<samp><span class="option">-mprototype</span></samp>, only calls to prototyped variable argument functions
set or clear the bit.
<br><dt><code>-msim</code><dd><a name="index-msim-2336"></a>On embedded PowerPC systems, assume that the startup module is called
<samp><span class="file">sim-crt0.o</span></samp> and that the standard C libraries are <samp><span class="file">libsim.a</span></samp> and
<samp><span class="file">libc.a</span></samp>. This is the default for &lsquo;<samp><span class="samp">powerpc-*-eabisim</span></samp>&rsquo;
configurations.
<br><dt><code>-mmvme</code><dd><a name="index-mmvme-2337"></a>On embedded PowerPC systems, assume that the startup module is called
<samp><span class="file">crt0.o</span></samp> and the standard C libraries are <samp><span class="file">libmvme.a</span></samp> and
<samp><span class="file">libc.a</span></samp>.
<br><dt><code>-mads</code><dd><a name="index-mads-2338"></a>On embedded PowerPC systems, assume that the startup module is called
<samp><span class="file">crt0.o</span></samp> and the standard C libraries are <samp><span class="file">libads.a</span></samp> and
<samp><span class="file">libc.a</span></samp>.
<br><dt><code>-myellowknife</code><dd><a name="index-myellowknife-2339"></a>On embedded PowerPC systems, assume that the startup module is called
<samp><span class="file">crt0.o</span></samp> and the standard C libraries are <samp><span class="file">libyk.a</span></samp> and
<samp><span class="file">libc.a</span></samp>.
<br><dt><code>-mvxworks</code><dd><a name="index-mvxworks-2340"></a>On System V.4 and embedded PowerPC systems, specify that you are
compiling for a VxWorks system.
<br><dt><code>-memb</code><dd><a name="index-memb-2341"></a>On embedded PowerPC systems, set the <code>PPC_EMB</code> bit in the ELF flags
header to indicate that &lsquo;<samp><span class="samp">eabi</span></samp>&rsquo; extended relocations are used.
<br><dt><code>-meabi</code><dt><code>-mno-eabi</code><dd><a name="index-meabi-2342"></a><a name="index-mno_002deabi-2343"></a>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 <samp><span class="option">-meabi</span></samp>
means that the stack is aligned to an 8-byte boundary, a function
<code>__eabi</code> is called from <code>main</code> to set up the EABI
environment, and the <samp><span class="option">-msdata</span></samp> option can use both <code>r2</code> and
<code>r13</code> to point to two separate small data areas. Selecting
<samp><span class="option">-mno-eabi</span></samp> means that the stack is aligned to a 16-byte boundary,
no EABI initialization function is called from <code>main</code>, and the
<samp><span class="option">-msdata</span></samp> option only uses <code>r13</code> to point to a single
small data area. The <samp><span class="option">-meabi</span></samp> option is on by default if you
configured GCC using one of the &lsquo;<samp><span class="samp">powerpc*-*-eabi*</span></samp>&rsquo; options.
<br><dt><code>-msdata=eabi</code><dd><a name="index-msdata_003deabi-2344"></a>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 <samp><span class="option">-msdata=eabi</span></samp> option is
incompatible with the <samp><span class="option">-mrelocatable</span></samp> option. The
<samp><span class="option">-msdata=eabi</span></samp> option also sets the <samp><span class="option">-memb</span></samp> option.
<br><dt><code>-msdata=sysv</code><dd><a name="index-msdata_003dsysv-2345"></a>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 <samp><span class="option">-msdata=sysv</span></samp> option is incompatible with the
<samp><span class="option">-mrelocatable</span></samp> option.
<br><dt><code>-msdata=default</code><dt><code>-msdata</code><dd><a name="index-msdata_003ddefault-2346"></a><a name="index-msdata-2347"></a>On System V.4 and embedded PowerPC systems, if <samp><span class="option">-meabi</span></samp> is used,
compile code the same as <samp><span class="option">-msdata=eabi</span></samp>, otherwise compile code the
same as <samp><span class="option">-msdata=sysv</span></samp>.
<br><dt><code>-msdata=data</code><dd><a name="index-msdata_003ddata-2348"></a>On System V.4 and embedded PowerPC systems, put small global
data in the <code>.sdata</code> section. Put small uninitialized global
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 <samp><span class="option">-msdata</span></samp> options are used.
<br><dt><code>-msdata=none</code><dt><code>-mno-sdata</code><dd><a name="index-msdata_003dnone-2349"></a><a name="index-mno_002dsdata-2350"></a>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>-mblock-move-inline-limit=</code><var>num</var><dd><a name="index-mblock_002dmove_002dinline_002dlimit-2351"></a>Inline all block moves (such as calls to <code>memcpy</code> or structure
copies) less than or equal to <var>num</var> bytes. The minimum value for
<var>num</var> is 32 bytes on 32-bit targets and 64 bytes on 64-bit
targets. The default value is target-specific.
<br><dt><code>-G </code><var>num</var><dd><a name="index-G-2352"></a><a name="index-smaller-data-references-_0028PowerPC_0029-2353"></a><a name="index-g_t_002esdata_002f_002esdata2-references-_0028PowerPC_0029-2354"></a>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
<samp><span class="option">-G </span><var>num</var></samp> switch is also passed to the linker.
All modules should be compiled with the same <samp><span class="option">-G </span><var>num</var></samp> value.
<br><dt><code>-mregnames</code><dt><code>-mno-regnames</code><dd><a name="index-mregnames-2355"></a><a name="index-mno_002dregnames-2356"></a>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><dt><code>-mno-longcall</code><dd><a name="index-mlongcall-2357"></a><a name="index-mno_002dlongcall-2358"></a>By default assume that all calls are far away so that a longer and more
expensive calling sequence is required. This is required for calls
farther than 32 megabytes (33,554,432 bytes) from the current location.
A short call is generated if the compiler knows
the call cannot be that far away. This setting can be overridden by
the <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>On Darwin/PPC systems, <code>#pragma longcall</code> generates <code>jbsr
callee, L42</code>, plus a <dfn>branch island</dfn> (glue code). The two target
addresses represent the callee and the branch island. The
Darwin/PPC linker prefers the first address and generates a <code>bl
callee</code> if the PPC <code>bl</code> instruction reaches the callee directly;
otherwise, the linker generates <code>bl L42</code> to call the branch
island. The branch island is appended to the body of the
calling function; it computes the full 32-bit address of the callee
and jumps to it.
<p>On Mach-O (Darwin) systems, this option directs the compiler emit to
the glue for every direct call, and the Darwin linker decides whether
to use or discard it.
<p>In the future, GCC may ignore all longcall specifications
when the linker is known to generate glue.
<br><dt><code>-mtls-markers</code><dt><code>-mno-tls-markers</code><dd><a name="index-mtls_002dmarkers-2359"></a><a name="index-mno_002dtls_002dmarkers-2360"></a>Mark (do not mark) calls to <code>__tls_get_addr</code> with a relocation
specifying the function argument. The relocation allows the linker to
reliably associate function call with argument setup instructions for
TLS optimization, which in turn allows GCC to better schedule the
sequence.
<br><dt><code>-pthread</code><dd><a name="index-pthread-2361"></a>Adds support for multithreading with the <dfn>pthreads</dfn> library.
This option sets flags for both the preprocessor and linker.
<br><dt><code>-mrecip</code><dt><code>-mno-recip</code><dd><a name="index-mrecip-2362"></a>This option enables use of the reciprocal estimate and
reciprocal square root estimate instructions with additional
Newton-Raphson steps to increase precision instead of doing a divide or
square root and divide for floating-point arguments. You should use
the <samp><span class="option">-ffast-math</span></samp> option when using <samp><span class="option">-mrecip</span></samp> (or at
least <samp><span class="option">-funsafe-math-optimizations</span></samp>,
<samp><span class="option">-finite-math-only</span></samp>, <samp><span class="option">-freciprocal-math</span></samp> and
<samp><span class="option">-fno-trapping-math</span></samp>). Note that while the throughput of the
sequence is generally higher than the throughput of the non-reciprocal
instruction, the precision of the sequence can be decreased by up to 2
ulp (i.e. the inverse of 1.0 equals 0.99999994) for reciprocal square
roots.
<br><dt><code>-mrecip=</code><var>opt</var><dd><a name="index-mrecip_003dopt-2363"></a>This option controls which reciprocal estimate instructions
may be used. <var>opt</var> is a comma-separated list of options, which may
be preceded by a <code>!</code> to invert the option:
<dl>
<dt>&lsquo;<samp><span class="samp">all</span></samp>&rsquo;<dd>Enable all estimate instructions.
<br><dt>&lsquo;<samp><span class="samp">default</span></samp>&rsquo;<dd>Enable the default instructions, equivalent to <samp><span class="option">-mrecip</span></samp>.
<br><dt>&lsquo;<samp><span class="samp">none</span></samp>&rsquo;<dd>Disable all estimate instructions, equivalent to <samp><span class="option">-mno-recip</span></samp>.
<br><dt>&lsquo;<samp><span class="samp">div</span></samp>&rsquo;<dd>Enable the reciprocal approximation instructions for both
single and double precision.
<br><dt>&lsquo;<samp><span class="samp">divf</span></samp>&rsquo;<dd>Enable the single-precision reciprocal approximation instructions.
<br><dt>&lsquo;<samp><span class="samp">divd</span></samp>&rsquo;<dd>Enable the double-precision reciprocal approximation instructions.
<br><dt>&lsquo;<samp><span class="samp">rsqrt</span></samp>&rsquo;<dd>Enable the reciprocal square root approximation instructions for both
single and double precision.
<br><dt>&lsquo;<samp><span class="samp">rsqrtf</span></samp>&rsquo;<dd>Enable the single-precision reciprocal square root approximation instructions.
<br><dt>&lsquo;<samp><span class="samp">rsqrtd</span></samp>&rsquo;<dd>Enable the double-precision reciprocal square root approximation instructions.
</dl>
<p>So, for example, <samp><span class="option">-mrecip=all,!rsqrtd</span></samp> enables
all of the reciprocal estimate instructions, except for the
<code>FRSQRTE</code>, <code>XSRSQRTEDP</code>, and <code>XVRSQRTEDP</code> instructions
which handle the double-precision reciprocal square root calculations.
<br><dt><code>-mrecip-precision</code><dt><code>-mno-recip-precision</code><dd><a name="index-mrecip_002dprecision-2364"></a>Assume (do not assume) that the reciprocal estimate instructions
provide higher-precision estimates than is mandated by the PowerPC
ABI. Selecting <samp><span class="option">-mcpu=power6</span></samp>, <samp><span class="option">-mcpu=power7</span></samp> or
<samp><span class="option">-mcpu=power8</span></samp> automatically selects <samp><span class="option">-mrecip-precision</span></samp>.
The double-precision square root estimate instructions are not generated by
default on low-precision machines, since they do not provide an
estimate that converges after three steps.
<br><dt><code>-mveclibabi=</code><var>type</var><dd><a name="index-mveclibabi-2365"></a>Specifies the ABI type to use for vectorizing intrinsics using an
external library. The only type supported at present is &lsquo;<samp><span class="samp">mass</span></samp>&rsquo;,
which specifies to use IBM's Mathematical Acceleration Subsystem
(MASS) libraries for vectorizing intrinsics using external libraries.
GCC currently emits calls to <code>acosd2</code>, <code>acosf4</code>,
<code>acoshd2</code>, <code>acoshf4</code>, <code>asind2</code>, <code>asinf4</code>,
<code>asinhd2</code>, <code>asinhf4</code>, <code>atan2d2</code>, <code>atan2f4</code>,
<code>atand2</code>, <code>atanf4</code>, <code>atanhd2</code>, <code>atanhf4</code>,
<code>cbrtd2</code>, <code>cbrtf4</code>, <code>cosd2</code>, <code>cosf4</code>,
<code>coshd2</code>, <code>coshf4</code>, <code>erfcd2</code>, <code>erfcf4</code>,
<code>erfd2</code>, <code>erff4</code>, <code>exp2d2</code>, <code>exp2f4</code>,
<code>expd2</code>, <code>expf4</code>, <code>expm1d2</code>, <code>expm1f4</code>,
<code>hypotd2</code>, <code>hypotf4</code>, <code>lgammad2</code>, <code>lgammaf4</code>,
<code>log10d2</code>, <code>log10f4</code>, <code>log1pd2</code>, <code>log1pf4</code>,
<code>log2d2</code>, <code>log2f4</code>, <code>logd2</code>, <code>logf4</code>,
<code>powd2</code>, <code>powf4</code>, <code>sind2</code>, <code>sinf4</code>, <code>sinhd2</code>,
<code>sinhf4</code>, <code>sqrtd2</code>, <code>sqrtf4</code>, <code>tand2</code>,
<code>tanf4</code>, <code>tanhd2</code>, and <code>tanhf4</code> when generating code
for power7. Both <samp><span class="option">-ftree-vectorize</span></samp> and
<samp><span class="option">-funsafe-math-optimizations</span></samp> must also be enabled. The MASS
libraries must be specified at link time.
<br><dt><code>-mfriz</code><dt><code>-mno-friz</code><dd><a name="index-mfriz-2366"></a>Generate (do not generate) the <code>friz</code> instruction when the
<samp><span class="option">-funsafe-math-optimizations</span></samp> option is used to optimize
rounding of floating-point values to 64-bit integer and back to floating
point. The <code>friz</code> instruction does not return the same value if
the floating-point number is too large to fit in an integer.
<br><dt><code>-mpointers-to-nested-functions</code><dt><code>-mno-pointers-to-nested-functions</code><dd><a name="index-mpointers_002dto_002dnested_002dfunctions-2367"></a>Generate (do not generate) code to load up the static chain register
(<code>r11</code>) when calling through a pointer on AIX and 64-bit Linux
systems where a function pointer points to a 3-word descriptor giving
the function address, TOC value to be loaded in register <code>r2</code>, and
static chain value to be loaded in register <code>r11</code>. The
<samp><span class="option">-mpointers-to-nested-functions</span></samp> is on by default. You cannot
call through pointers to nested functions or pointers
to functions compiled in other languages that use the static chain if
you use <samp><span class="option">-mno-pointers-to-nested-functions</span></samp>.
<br><dt><code>-msave-toc-indirect</code><dt><code>-mno-save-toc-indirect</code><dd><a name="index-msave_002dtoc_002dindirect-2368"></a>Generate (do not generate) code to save the TOC value in the reserved
stack location in the function prologue if the function calls through
a pointer on AIX and 64-bit Linux systems. If the TOC value is not
saved in the prologue, it is saved just before the call through the
pointer. The <samp><span class="option">-mno-save-toc-indirect</span></samp> option is the default.
<br><dt><code>-mcompat-align-parm</code><dt><code>-mno-compat-align-parm</code><dd><a name="index-mcompat_002dalign_002dparm-2369"></a>Generate (do not generate) code to pass structure parameters with a
maximum alignment of 64 bits, for compatibility with older versions
of GCC.
<p>Older versions of GCC (prior to 4.9.0) incorrectly did not align a
structure parameter on a 128-bit boundary when that structure contained
a member requiring 128-bit alignment. This is corrected in more
recent versions of GCC. This option may be used to generate code
that is compatible with functions compiled with older versions of
GCC.
<p>The <samp><span class="option">-mno-compat-align-parm</span></samp> option is the default.
</dl>
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