You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
101 lines
7.7 KiB
HTML
101 lines
7.7 KiB
HTML
15 years ago
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>i386-Arch - Using as</title>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html">
|
||
|
|
<meta name="description" content="Using as">
|
||
|
|
<meta name="generator" content="makeinfo 4.7">
|
||
|
|
<link title="Top" rel="start" href="index.html#Top">
|
||
|
|
<link rel="up" href="i386_002dDependent.html#i386_002dDependent" title="i386-Dependent">
|
||
|
|
<link rel="prev" href="i386_002d16bit.html#i386_002d16bit" title="i386-16bit">
|
||
|
|
<link rel="next" href="i386_002dBugs.html#i386_002dBugs" title="i386-Bugs">
|
||
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
||
|
|
<!--
|
||
|
|
This file documents the GNU Assembler "as".
|
||
|
|
|
||
|
|
Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
|
||
|
|
2006, 2007 Free Software Foundation, Inc.
|
||
|
|
|
||
|
|
Permission is granted to copy, distribute and/or modify this document
|
||
|
|
under the terms of the GNU Free Documentation License, Version 1.1
|
||
|
|
or any later version published by the Free Software Foundation;
|
||
|
|
with no Invariant Sections, with no Front-Cover Texts, and with no
|
||
|
|
Back-Cover Texts. A copy of the license is included in the
|
||
|
|
section entitled ``GNU Free Documentation License''.
|
||
|
|
|
||
|
|
man end-->
|
||
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
||
|
|
<style type="text/css"><!--
|
||
|
|
pre.display { font-family:inherit }
|
||
|
|
pre.format { font-family:inherit }
|
||
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallexample { font-size:smaller }
|
||
|
|
pre.smalllisp { font-size:smaller }
|
||
|
|
span.sc { font-variant:small-caps }
|
||
|
|
span.roman { font-family: serif; font-weight: normal; }
|
||
|
|
--></style>
|
||
|
|
</head>
|
||
|
|
<body>
|
||
|
|
<div class="node">
|
||
|
|
<p>
|
||
|
|
<a name="i386_002dArch"></a>Next: <a rel="next" accesskey="n" href="i386_002dBugs.html#i386_002dBugs">i386-Bugs</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="i386_002d16bit.html#i386_002d16bit">i386-16bit</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="i386_002dDependent.html#i386_002dDependent">i386-Dependent</a>
|
||
|
|
<hr><br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">9.13.14 Specifying CPU Architecture</h4>
|
||
|
|
|
||
|
|
<p><a name="index-arch-directive_002c-i386-957"></a><a name="index-i386-arch-directive-958"></a><a name="index-arch-directive_002c-x86_002d64-959"></a><a name="index-x86_002d64-arch-directive-960"></a>
|
||
|
|
<code>as</code> may be told to assemble for a particular CPU
|
||
|
|
(sub-)architecture with the <code>.arch </code><var>cpu_type</var> directive. This
|
||
|
|
directive enables a warning when gas detects an instruction that is not
|
||
|
|
supported on the CPU specified. The choices for <var>cpu_type</var> are:
|
||
|
|
|
||
|
|
<p><table summary=""><tr align="left"><td valign="top" width="20%"><span class="samp">i8086</span> </td><td valign="top" width="20%"><span class="samp">i186</span> </td><td valign="top" width="20%"><span class="samp">i286</span> </td><td valign="top" width="20%"><span class="samp">i386</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">i486</span> </td><td valign="top" width="20%"><span class="samp">i586</span> </td><td valign="top" width="20%"><span class="samp">i686</span> </td><td valign="top" width="20%"><span class="samp">pentium</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">pentiumpro</span> </td><td valign="top" width="20%"><span class="samp">pentiumii</span> </td><td valign="top" width="20%"><span class="samp">pentiumiii</span> </td><td valign="top" width="20%"><span class="samp">pentium4</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">prescott</span> </td><td valign="top" width="20%"><span class="samp">nocona</span> </td><td valign="top" width="20%"><span class="samp">core</span> </td><td valign="top" width="20%"><span class="samp">core2</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">k6</span> </td><td valign="top" width="20%"><span class="samp">k6_2</span> </td><td valign="top" width="20%"><span class="samp">athlon</span> </td><td valign="top" width="20%"><span class="samp">k8</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">amdfam10</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">generic32</span> </td><td valign="top" width="20%"><span class="samp">generic64</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">.mmx</span> </td><td valign="top" width="20%"><span class="samp">.sse</span> </td><td valign="top" width="20%"><span class="samp">.sse2</span> </td><td valign="top" width="20%"><span class="samp">.sse3</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">.ssse3</span> </td><td valign="top" width="20%"><span class="samp">.sse4.1</span> </td><td valign="top" width="20%"><span class="samp">.sse4.2</span> </td><td valign="top" width="20%"><span class="samp">.sse4</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">.avx</span> </td><td valign="top" width="20%"><span class="samp">.vmx</span> </td><td valign="top" width="20%"><span class="samp">.smx</span> </td><td valign="top" width="20%"><span class="samp">.xsave</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">.aes</span> </td><td valign="top" width="20%"><span class="samp">.pclmul</span> </td><td valign="top" width="20%"><span class="samp">.fma</span> </td><td valign="top" width="20%"><span class="samp">.movbe</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">.ept</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">.3dnow</span> </td><td valign="top" width="20%"><span class="samp">.3dnowa</span> </td><td valign="top" width="20%"><span class="samp">.sse4a</span> </td><td valign="top" width="20%"><span class="samp">.sse5</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">.svme</span> </td><td valign="top" width="20%"><span class="samp">.abm</span>
|
||
|
|
<br></td></tr><tr align="left"><td valign="top" width="20%"><span class="samp">.padlock</span>
|
||
|
|
<br></td></tr></table>
|
||
|
|
|
||
|
|
<p>Apart from the warning, there are only two other effects on
|
||
|
|
<code>as</code> operation; Firstly, if you specify a CPU other than
|
||
|
|
<span class="samp">i486</span>, then shift by one instructions such as <span class="samp">sarl $1, %eax</span>
|
||
|
|
will automatically use a two byte opcode sequence. The larger three
|
||
|
|
byte opcode sequence is used on the 486 (and when no architecture is
|
||
|
|
specified) because it executes faster on the 486. Note that you can
|
||
|
|
explicitly request the two byte opcode by writing <span class="samp">sarl %eax</span>.
|
||
|
|
Secondly, if you specify <span class="samp">i8086</span>, <span class="samp">i186</span>, or <span class="samp">i286</span>,
|
||
|
|
<em>and</em> <span class="samp">.code16</span> or <span class="samp">.code16gcc</span> then byte offset
|
||
|
|
conditional jumps will be promoted when necessary to a two instruction
|
||
|
|
sequence consisting of a conditional jump of the opposite sense around
|
||
|
|
an unconditional jump to the target.
|
||
|
|
|
||
|
|
<p>Following the CPU architecture (but not a sub-architecture, which are those
|
||
|
|
starting with a dot), you may specify <span class="samp">jumps</span> or <span class="samp">nojumps</span> to
|
||
|
|
control automatic promotion of conditional jumps. <span class="samp">jumps</span> is the
|
||
|
|
default, and enables jump promotion; All external jumps will be of the long
|
||
|
|
variety, and file-local jumps will be promoted as necessary.
|
||
|
|
(see <a href="i386_002dJumps.html#i386_002dJumps">i386-Jumps</a>) <span class="samp">nojumps</span> leaves external conditional jumps as
|
||
|
|
byte offset jumps, and warns about file-local conditional jumps that
|
||
|
|
<code>as</code> promotes.
|
||
|
|
Unconditional jumps are treated as for <span class="samp">jumps</span>.
|
||
|
|
|
||
|
|
<p>For example
|
||
|
|
|
||
|
|
<pre class="smallexample"> .arch i8086,nojumps
|
||
|
|
</pre>
|
||
|
|
</body></html>
|
||
|
|
|