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133 lines
6.7 KiB
HTML
133 lines
6.7 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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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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-->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>i386-Float (Using as)</title>
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<meta name="description" content="i386-Float (Using as)">
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<meta name="keywords" content="i386-Float (Using as)">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="AS-Index.html#AS-Index" rel="index" title="AS Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="i386_002dDependent.html#i386_002dDependent" rel="up" title="i386-Dependent">
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<link href="i386_002dSIMD.html#i386_002dSIMD" rel="next" title="i386-SIMD">
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<link href="i386_002dJumps.html#i386_002dJumps" rel="prev" title="i386-Jumps">
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</style>
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</head>
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<body lang="en">
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<a name="i386_002dFloat"></a>
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<div class="header">
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<p>
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Next: <a href="i386_002dSIMD.html#i386_002dSIMD" accesskey="n" rel="next">i386-SIMD</a>, Previous: <a href="i386_002dJumps.html#i386_002dJumps" accesskey="p" rel="prev">i386-Jumps</a>, Up: <a href="i386_002dDependent.html#i386_002dDependent" accesskey="u" rel="up">i386-Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Floating-Point-7"></a>
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<h4 class="subsection">9.15.9 Floating Point</h4>
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<a name="index-i386-floating-point"></a>
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<a name="index-floating-point_002c-i386"></a>
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<a name="index-x86_002d64-floating-point"></a>
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<a name="index-floating-point_002c-x86_002d64"></a>
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<p>All 80387 floating point types except packed BCD are supported.
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(BCD support may be added without much difficulty). These data
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types are 16-, 32-, and 64- bit integers, and single (32-bit),
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double (64-bit), and extended (80-bit) precision floating point.
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Each supported type has an instruction mnemonic suffix and a constructor
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associated with it. Instruction mnemonic suffixes specify the operand’s
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data type. Constructors build these data types into memory.
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</p>
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<a name="index-float-directive_002c-i386"></a>
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<a name="index-single-directive_002c-i386"></a>
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<a name="index-double-directive_002c-i386"></a>
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<a name="index-tfloat-directive_002c-i386"></a>
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<a name="index-float-directive_002c-x86_002d64"></a>
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<a name="index-single-directive_002c-x86_002d64"></a>
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<a name="index-double-directive_002c-x86_002d64"></a>
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<a name="index-tfloat-directive_002c-x86_002d64"></a>
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<ul>
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<li> Floating point constructors are ‘<samp>.float</samp>’ or ‘<samp>.single</samp>’,
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‘<samp>.double</samp>’, and ‘<samp>.tfloat</samp>’ for 32-, 64-, and 80-bit formats.
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These correspond to instruction mnemonic suffixes ‘<samp>s</samp>’, ‘<samp>l</samp>’,
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and ‘<samp>t</samp>’. ‘<samp>t</samp>’ stands for 80-bit (ten byte) real. The 80387
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only supports this format via the ‘<samp>fldt</samp>’ (load 80-bit real to stack
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top) and ‘<samp>fstpt</samp>’ (store 80-bit real and pop stack) instructions.
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</li><li> <a name="index-word-directive_002c-i386"></a>
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<a name="index-long-directive_002c-i386"></a>
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<a name="index-int-directive_002c-i386"></a>
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<a name="index-quad-directive_002c-i386"></a>
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<a name="index-word-directive_002c-x86_002d64"></a>
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<a name="index-long-directive_002c-x86_002d64"></a>
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<a name="index-int-directive_002c-x86_002d64"></a>
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<a name="index-quad-directive_002c-x86_002d64"></a>
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Integer constructors are ‘<samp>.word</samp>’, ‘<samp>.long</samp>’ or ‘<samp>.int</samp>’, and
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‘<samp>.quad</samp>’ for the 16-, 32-, and 64-bit integer formats. The
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corresponding instruction mnemonic suffixes are ‘<samp>s</samp>’ (single),
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‘<samp>l</samp>’ (long), and ‘<samp>q</samp>’ (quad). As with the 80-bit real format,
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the 64-bit ‘<samp>q</samp>’ format is only present in the ‘<samp>fildq</samp>’ (load
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quad integer to stack top) and ‘<samp>fistpq</samp>’ (store quad integer and pop
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stack) instructions.
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</li></ul>
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<p>Register to register operations should not use instruction mnemonic suffixes.
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‘<samp>fstl %st, %st(1)</samp>’ will give a warning, and be assembled as if you
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wrote ‘<samp>fst %st, %st(1)</samp>’, since all register to register operations
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use 80-bit floating point operands. (Contrast this with ‘<samp>fstl %st, mem</samp>’,
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which converts ‘<samp>%st</samp>’ from 80-bit to 64-bit floating point format,
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then stores the result in the 4 byte location ‘<samp>mem</samp>’)
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="i386_002dSIMD.html#i386_002dSIMD" accesskey="n" rel="next">i386-SIMD</a>, Previous: <a href="i386_002dJumps.html#i386_002dJumps" accesskey="p" rel="prev">i386-Jumps</a>, Up: <a href="i386_002dDependent.html#i386_002dDependent" accesskey="u" rel="up">i386-Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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