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121 lines
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<title>i386-Arch - Using as</title>
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<meta name="description" content="Using as">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="i386_002dDependent.html#i386_002dDependent" title="i386-Dependent">
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<link rel="prev" href="i386_002d16bit.html#i386_002d16bit" title="i386-16bit">
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<link rel="next" href="i386_002dBugs.html#i386_002dBugs" title="i386-Bugs">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled ``GNU Free Documentation License''.
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</head>
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<body>
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<div class="node">
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<a name="i386-Arch"></a>
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<a name="i386_002dArch"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="i386_002dBugs.html#i386_002dBugs">i386-Bugs</a>,
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Previous: <a rel="previous" accesskey="p" href="i386_002d16bit.html#i386_002d16bit">i386-16bit</a>,
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Up: <a rel="up" accesskey="u" href="i386_002dDependent.html#i386_002dDependent">i386-Dependent</a>
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<hr>
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</div>
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<h4 class="subsection">9.16.15 Specifying CPU Architecture</h4>
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<p><a name="index-arch-directive_002c-i386-1269"></a><a name="index-i386-arch-directive-1270"></a><a name="index-arch-directive_002c-x86_002d64-1271"></a><a name="index-x86_002d64-arch-directive-1272"></a>
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<code>as</code> may be told to assemble for a particular CPU
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(sub-)architecture with the <code>.arch </code><var>cpu_type</var> directive. This
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directive enables a warning when gas detects an instruction that is not
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supported on the CPU specified. The choices for <var>cpu_type</var> are:
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<p><table summary=""><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">i8086</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">i186</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">i286</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">i386</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">i486</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">i586</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">i686</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">pentium</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">pentiumpro</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">pentiumii</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">pentiumiii</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">pentium4</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">prescott</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">nocona</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">core</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">core2</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">corei7</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">l1om</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">k1om</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">iamcu</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">k6</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">k6_2</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">athlon</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">k8</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">amdfam10</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">bdver1</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">bdver2</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">bdver3</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">bdver4</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">znver1</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">znver2</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">btver1</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">btver2</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">generic32</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">generic64</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.cmov</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.fxsr</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.mmx</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.sse</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.sse2</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.sse3</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.ssse3</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.sse4.1</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.sse4.2</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.sse4</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.avx</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.vmx</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.smx</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.ept</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.clflush</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.movbe</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.xsave</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.xsaveopt</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.aes</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.pclmul</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.fma</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.fsgsbase</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.rdrnd</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.f16c</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx2</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.bmi2</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.lzcnt</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.invpcid</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.vmfunc</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.hle</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.rtm</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.adx</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.rdseed</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.prfchw</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.smap</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.mpx</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.sha</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.prefetchwt1</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.clflushopt</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.xsavec</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.xsaves</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.se1</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.avx512f</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512cd</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512er</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512pf</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.avx512vl</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512bw</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512dq</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512ifma</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.avx512vbmi</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512_4fmaps</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512_4vnniw</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.avx512_vpopcntdq</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512_vbmi2</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512_vnni</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.avx512_bitalg</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512_bf16</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.avx512_vp2intersect</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.clwb</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.rdpid</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.ptwrite</span></samp>’ </td><td valign="top" width="20%"><br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.ibt</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.wbnoinvd</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.pconfig</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.waitpkg</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.cldemote</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.shstk</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.gfni</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.vaes</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.vpclmulqdq</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.movdiri</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.movdir64b</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.enqcmd</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.3dnow</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.3dnowa</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.sse4a</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.sse5</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.syscall</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.rdtscp</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.svme</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.abm</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.lwp</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.fma4</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.xop</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.cx16</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">.padlock</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.clzero</span></samp>’ </td><td valign="top" width="20%">‘<samp><span class="samp">.mwaitx</span></samp>’
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<br></td></tr></table>
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<p>Apart from the warning, there are only two other effects on
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<code>as</code> operation; Firstly, if you specify a CPU other than
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‘<samp><span class="samp">i486</span></samp>’, then shift by one instructions such as ‘<samp><span class="samp">sarl $1, %eax</span></samp>’
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will automatically use a two byte opcode sequence. The larger three
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byte opcode sequence is used on the 486 (and when no architecture is
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specified) because it executes faster on the 486. Note that you can
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explicitly request the two byte opcode by writing ‘<samp><span class="samp">sarl %eax</span></samp>’.
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Secondly, if you specify ‘<samp><span class="samp">i8086</span></samp>’, ‘<samp><span class="samp">i186</span></samp>’, or ‘<samp><span class="samp">i286</span></samp>’,
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<em>and</em> ‘<samp><span class="samp">.code16</span></samp>’ or ‘<samp><span class="samp">.code16gcc</span></samp>’ then byte offset
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conditional jumps will be promoted when necessary to a two instruction
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sequence consisting of a conditional jump of the opposite sense around
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an unconditional jump to the target.
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<p>Following the CPU architecture (but not a sub-architecture, which are those
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starting with a dot), you may specify ‘<samp><span class="samp">jumps</span></samp>’ or ‘<samp><span class="samp">nojumps</span></samp>’ to
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control automatic promotion of conditional jumps. ‘<samp><span class="samp">jumps</span></samp>’ is the
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default, and enables jump promotion; All external jumps will be of the long
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variety, and file-local jumps will be promoted as necessary.
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(see <a href="i386_002dJumps.html#i386_002dJumps">i386-Jumps</a>) ‘<samp><span class="samp">nojumps</span></samp>’ leaves external conditional jumps as
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byte offset jumps, and warns about file-local conditional jumps that
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<code>as</code> promotes.
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Unconditional jumps are treated as for ‘<samp><span class="samp">jumps</span></samp>’.
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<p>For example
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<pre class="smallexample"> .arch i8086,nojumps
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</pre>
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