<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>