84 lines
5.6 KiB
HTML
84 lines
5.6 KiB
HTML
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>i386-Float - 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_002dJumps.html#i386_002dJumps" title="i386-Jumps">
|
||
|
|
<link rel="next" href="i386_002dSIMD.html#i386_002dSIMD" title="i386-SIMD">
|
||
|
|
<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_002dFloat"></a>Next: <a rel="next" accesskey="n" href="i386_002dSIMD.html#i386_002dSIMD">i386-SIMD</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="i386_002dJumps.html#i386_002dJumps">i386-Jumps</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="i386_002dDependent.html#i386_002dDependent">i386-Dependent</a>
|
||
|
|
<hr><br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">9.13.10 Floating Point</h4>
|
||
|
|
|
||
|
|
<p><a name="index-i386-floating-point-923"></a><a name="index-floating-point_002c-i386-924"></a><a name="index-x86_002d64-floating-point-925"></a><a name="index-floating-point_002c-x86_002d64-926"></a>All 80387 floating point types except packed BCD are supported.
|
||
|
|
(BCD support may be added without much difficulty). These data
|
||
|
|
types are 16-, 32-, and 64- bit integers, and single (32-bit),
|
||
|
|
double (64-bit), and extended (80-bit) precision floating point.
|
||
|
|
Each supported type has an instruction mnemonic suffix and a constructor
|
||
|
|
associated with it. Instruction mnemonic suffixes specify the operand's
|
||
|
|
data type. Constructors build these data types into memory.
|
||
|
|
|
||
|
|
<p><a name="index-_0040code_007bfloat_007d-directive_002c-i386-927"></a><a name="index-_0040code_007bsingle_007d-directive_002c-i386-928"></a><a name="index-_0040code_007bdouble_007d-directive_002c-i386-929"></a><a name="index-_0040code_007btfloat_007d-directive_002c-i386-930"></a><a name="index-_0040code_007bfloat_007d-directive_002c-x86_002d64-931"></a><a name="index-_0040code_007bsingle_007d-directive_002c-x86_002d64-932"></a><a name="index-_0040code_007bdouble_007d-directive_002c-x86_002d64-933"></a><a name="index-_0040code_007btfloat_007d-directive_002c-x86_002d64-934"></a>
|
||
|
|
<ul>
|
||
|
|
<li>Floating point constructors are <span class="samp">.float</span> or <span class="samp">.single</span>,
|
||
|
|
<span class="samp">.double</span>, and <span class="samp">.tfloat</span> for 32-, 64-, and 80-bit formats.
|
||
|
|
These correspond to instruction mnemonic suffixes <span class="samp">s</span>, <span class="samp">l</span>,
|
||
|
|
and <span class="samp">t</span>. <span class="samp">t</span> stands for 80-bit (ten byte) real. The 80387
|
||
|
|
only supports this format via the <span class="samp">fldt</span> (load 80-bit real to stack
|
||
|
|
top) and <span class="samp">fstpt</span> (store 80-bit real and pop stack) instructions.
|
||
|
|
|
||
|
|
<p><a name="index-_0040code_007bword_007d-directive_002c-i386-935"></a><a name="index-_0040code_007blong_007d-directive_002c-i386-936"></a><a name="index-_0040code_007bint_007d-directive_002c-i386-937"></a><a name="index-_0040code_007bquad_007d-directive_002c-i386-938"></a><a name="index-_0040code_007bword_007d-directive_002c-x86_002d64-939"></a><a name="index-_0040code_007blong_007d-directive_002c-x86_002d64-940"></a><a name="index-_0040code_007bint_007d-directive_002c-x86_002d64-941"></a><a name="index-_0040code_007bquad_007d-directive_002c-x86_002d64-942"></a><li>Integer constructors are <span class="samp">.word</span>, <span class="samp">.long</span> or <span class="samp">.int</span>, and
|
||
|
|
<span class="samp">.quad</span> for the 16-, 32-, and 64-bit integer formats. The
|
||
|
|
corresponding instruction mnemonic suffixes are <span class="samp">s</span> (single),
|
||
|
|
<span class="samp">l</span> (long), and <span class="samp">q</span> (quad). As with the 80-bit real format,
|
||
|
|
the 64-bit <span class="samp">q</span> format is only present in the <span class="samp">fildq</span> (load
|
||
|
|
quad integer to stack top) and <span class="samp">fistpq</span> (store quad integer and pop
|
||
|
|
stack) instructions.
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<p>Register to register operations should not use instruction mnemonic suffixes.
|
||
|
|
<span class="samp">fstl %st, %st(1)</span> will give a warning, and be assembled as if you
|
||
|
|
wrote <span class="samp">fst %st, %st(1)</span>, since all register to register operations
|
||
|
|
use 80-bit floating point operands. (Contrast this with <span class="samp">fstl %st, mem</span>,
|
||
|
|
which converts <span class="samp">%st</span> from 80-bit to 64-bit floating point format,
|
||
|
|
then stores the result in the 4 byte location <span class="samp">mem</span>)
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|