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| <h4 class="subsection">9.13.1 Options</h4> |
| |
| <p><a name="index-options-for-i386-844"></a><a name="index-options-for-x86_002d64-845"></a><a name="index-i386-options-846"></a><a name="index-x86_002d64-options-847"></a> |
| The i386 version of <code>as</code> has a few machine |
| dependent options: |
| |
| |
| <a name="index-g_t_0040samp_007b_002d_002d32_007d-option_002c-i386-848"></a> |
| <a name="index-g_t_0040samp_007b_002d_002d32_007d-option_002c-x86_002d64-849"></a> |
| <a name="index-g_t_0040samp_007b_002d_002d64_007d-option_002c-i386-850"></a> |
| <a name="index-g_t_0040samp_007b_002d_002d64_007d-option_002c-x86_002d64-851"></a> |
| <dl><dt><code>--32 | --64</code><dd>Select the word size, either 32 bits or 64 bits. Selecting 32-bit |
| implies Intel i386 architecture, while 64-bit implies AMD x86-64 |
| architecture. |
| |
| <p>These options are only available with the ELF object file format, and |
| require that the necessary BFD support has been included (on a 32-bit |
| platform you have to add –enable-64-bit-bfd to configure enable 64-bit |
| usage and use x86-64 as target platform). |
| |
| <br><dt><code>-n</code><dd>By default, x86 GAS replaces multiple nop instructions used for |
| alignment within code sections with multi-byte nop instructions such |
| as leal 0(%esi,1),%esi. This switch disables the optimization. |
| |
| <p><a name="index-g_t_0040samp_007b_002d_002ddivide_007d-option_002c-i386-852"></a><br><dt><code>--divide</code><dd>On SVR4-derived platforms, the character ‘<samp><span class="samp">/</span></samp>’ is treated as a comment |
| character, which means that it cannot be used in expressions. The |
| ‘<samp><span class="samp">--divide</span></samp>’ option turns ‘<samp><span class="samp">/</span></samp>’ into a normal character. This does |
| not disable ‘<samp><span class="samp">/</span></samp>’ at the beginning of a line starting a comment, or |
| affect using ‘<samp><span class="samp">#</span></samp>’ for starting a comment. |
| |
| <p><a name="index-g_t_0040samp_007b_002dmarch_003d_007d-option_002c-i386-853"></a><a name="index-g_t_0040samp_007b_002dmarch_003d_007d-option_002c-x86_002d64-854"></a><br><dt><code>-march=</code><var>CPU</var><code>[+</code><var>EXTENSION</var><code>...]</code><dd>This option specifies the target processor. The assembler will |
| issue an error message if an attempt is made to assemble an instruction |
| which will not execute on the target processor. The following |
| processor names are recognized: |
| <code>i8086</code>, |
| <code>i186</code>, |
| <code>i286</code>, |
| <code>i386</code>, |
| <code>i486</code>, |
| <code>i586</code>, |
| <code>i686</code>, |
| <code>pentium</code>, |
| <code>pentiumpro</code>, |
| <code>pentiumii</code>, |
| <code>pentiumiii</code>, |
| <code>pentium4</code>, |
| <code>prescott</code>, |
| <code>nocona</code>, |
| <code>core</code>, |
| <code>core2</code>, |
| <code>corei7</code>, |
| <code>l1om</code>, |
| <code>k6</code>, |
| <code>k6_2</code>, |
| <code>athlon</code>, |
| <code>opteron</code>, |
| <code>k8</code>, |
| <code>amdfam10</code>, |
| <code>bdver1</code>, |
| <code>generic32</code> and |
| <code>generic64</code>. |
| |
| <p>In addition to the basic instruction set, the assembler can be told to |
| accept various extension mnemonics. For example, |
| <code>-march=i686+sse4+vmx</code> extends <var>i686</var> with <var>sse4</var> and |
| <var>vmx</var>. The following extensions are currently supported: |
| <code>8087</code>, |
| <code>287</code>, |
| <code>387</code>, |
| <code>no87</code>, |
| <code>mmx</code>, |
| <code>nommx</code>, |
| <code>sse</code>, |
| <code>sse2</code>, |
| <code>sse3</code>, |
| <code>ssse3</code>, |
| <code>sse4.1</code>, |
| <code>sse4.2</code>, |
| <code>sse4</code>, |
| <code>nosse</code>, |
| <code>avx</code>, |
| <code>noavx</code>, |
| <code>vmx</code>, |
| <code>smx</code>, |
| <code>xsave</code>, |
| <code>xsaveopt</code>, |
| <code>aes</code>, |
| <code>pclmul</code>, |
| <code>fsgsbase</code>, |
| <code>rdrnd</code>, |
| <code>f16c</code>, |
| <code>fma</code>, |
| <code>movbe</code>, |
| <code>ept</code>, |
| <code>clflush</code>, |
| <code>lwp</code>, |
| <code>fma4</code>, |
| <code>xop</code>, |
| <code>syscall</code>, |
| <code>rdtscp</code>, |
| <code>3dnow</code>, |
| <code>3dnowa</code>, |
| <code>sse4a</code>, |
| <code>sse5</code>, |
| <code>svme</code>, |
| <code>abm</code> and |
| <code>padlock</code>. |
| Note that rather than extending a basic instruction set, the extension |
| mnemonics starting with <code>no</code> revoke the respective functionality. |
| |
| <p>When the <code>.arch</code> directive is used with <samp><span class="option">-march</span></samp>, the |
| <code>.arch</code> directive will take precedent. |
| |
| <p><a name="index-g_t_0040samp_007b_002dmtune_003d_007d-option_002c-i386-855"></a><a name="index-g_t_0040samp_007b_002dmtune_003d_007d-option_002c-x86_002d64-856"></a><br><dt><code>-mtune=</code><var>CPU</var><dd>This option specifies a processor to optimize for. When used in |
| conjunction with the <samp><span class="option">-march</span></samp> option, only instructions |
| of the processor specified by the <samp><span class="option">-march</span></samp> option will be |
| generated. |
| |
| <p>Valid <var>CPU</var> values are identical to the processor list of |
| <samp><span class="option">-march=</span><var>CPU</var></samp>. |
| |
| <p><a name="index-g_t_0040samp_007b_002dmsse2avx_007d-option_002c-i386-857"></a><a name="index-g_t_0040samp_007b_002dmsse2avx_007d-option_002c-x86_002d64-858"></a><br><dt><code>-msse2avx</code><dd>This option specifies that the assembler should encode SSE instructions |
| with VEX prefix. |
| |
| <p><a name="index-g_t_0040samp_007b_002dmsse_002dcheck_003d_007d-option_002c-i386-859"></a><a name="index-g_t_0040samp_007b_002dmsse_002dcheck_003d_007d-option_002c-x86_002d64-860"></a><br><dt><code>-msse-check=</code><var>none</var><dt><code>-msse-check=</code><var>warning</var><dt><code>-msse-check=</code><var>error</var><dd>These options control if the assembler should check SSE intructions. |
| <samp><span class="option">-msse-check=</span><var>none</var></samp> will make the assembler not to check SSE |
| instructions, which is the default. <samp><span class="option">-msse-check=</span><var>warning</var></samp> |
| will make the assembler issue a warning for any SSE intruction. |
| <samp><span class="option">-msse-check=</span><var>error</var></samp> will make the assembler issue an error |
| for any SSE intruction. |
| |
| <p><a name="index-g_t_0040samp_007b_002dmavxscalar_003d_007d-option_002c-i386-861"></a><a name="index-g_t_0040samp_007b_002dmavxscalar_003d_007d-option_002c-x86_002d64-862"></a><br><dt><code>-mavxscalar=</code><var>128</var><dt><code>-mavxscalar=</code><var>256</var><dd>This options control how the assembler should encode scalar AVX |
| instructions. <samp><span class="option">-mavxscalar=</span><var>128</var></samp> will encode scalar |
| AVX instructions with 128bit vector length, which is the default. |
| <samp><span class="option">-mavxscalar=</span><var>256</var></samp> will encode scalar AVX instructions |
| with 256bit vector length. |
| |
| <p><a name="index-g_t_0040samp_007b_002dmmnemonic_003d_007d-option_002c-i386-863"></a><a name="index-g_t_0040samp_007b_002dmmnemonic_003d_007d-option_002c-x86_002d64-864"></a><br><dt><code>-mmnemonic=</code><var>att</var><dt><code>-mmnemonic=</code><var>intel</var><dd>This option specifies instruction mnemonic for matching instructions. |
| The <code>.att_mnemonic</code> and <code>.intel_mnemonic</code> directives will |
| take precedent. |
| |
| <p><a name="index-g_t_0040samp_007b_002dmsyntax_003d_007d-option_002c-i386-865"></a><a name="index-g_t_0040samp_007b_002dmsyntax_003d_007d-option_002c-x86_002d64-866"></a><br><dt><code>-msyntax=</code><var>att</var><dt><code>-msyntax=</code><var>intel</var><dd>This option specifies instruction syntax when processing instructions. |
| The <code>.att_syntax</code> and <code>.intel_syntax</code> directives will |
| take precedent. |
| |
| <p><a name="index-g_t_0040samp_007b_002dmnaked_002dreg_007d-option_002c-i386-867"></a><a name="index-g_t_0040samp_007b_002dmnaked_002dreg_007d-option_002c-x86_002d64-868"></a><br><dt><code>-mnaked-reg</code><dd>This opetion specifies that registers don't require a ‘<samp><span class="samp">%</span></samp>’ prefix. |
| The <code>.att_syntax</code> and <code>.intel_syntax</code> directives will take precedent. |
| |
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