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95 lines
4.4 KiB
HTML
95 lines
4.4 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 manual describes how to install and use the GNU multiple precision
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arithmetic library, version 6.1.0.
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Copyright 1991, 1993-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document under
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the terms of the GNU Free Documentation License, Version 1.3 or any later
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version published by the Free Software Foundation; with no Invariant Sections,
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with the Front-Cover Texts being "A GNU Manual", and with the Back-Cover
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Texts being "You have freedom to copy and modify this GNU Manual, like GNU
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software". A copy of the license is included in
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GNU Free Documentation License. -->
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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>Assembly Basics (GNU MP 6.1.0)</title>
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<meta name="description" content="How to install and use the GNU multiple precision arithmetic library, version 6.1.0.">
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<meta name="keywords" content="Assembly Basics (GNU MP 6.1.0)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="Assembly-Coding.html#Assembly-Coding" rel="up" title="Assembly Coding">
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<link href="Assembly-Carry-Propagation.html#Assembly-Carry-Propagation" rel="next" title="Assembly Carry Propagation">
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<link href="Assembly-Code-Organisation.html#Assembly-Code-Organisation" rel="prev" title="Assembly Code Organisation">
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Assembly-Basics"></a>
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<div class="header">
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<p>
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Next: <a href="Assembly-Carry-Propagation.html#Assembly-Carry-Propagation" accesskey="n" rel="next">Assembly Carry Propagation</a>, Previous: <a href="Assembly-Code-Organisation.html#Assembly-Code-Organisation" accesskey="p" rel="prev">Assembly Code Organisation</a>, Up: <a href="Assembly-Coding.html#Assembly-Coding" accesskey="u" rel="up">Assembly Coding</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Assembly-Basics-1"></a>
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<h4 class="subsection">15.8.2 Assembly Basics</h4>
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<p><code>mpn_addmul_1</code> and <code>mpn_submul_1</code> are the most important routines
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for overall GMP performance. All multiplications and divisions come down to
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repeated calls to these. <code>mpn_add_n</code>, <code>mpn_sub_n</code>,
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<code>mpn_lshift</code> and <code>mpn_rshift</code> are next most important.
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</p>
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<p>On some CPUs assembly versions of the internal functions
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<code>mpn_mul_basecase</code> and <code>mpn_sqr_basecase</code> give significant speedups,
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mainly through avoiding function call overheads. They can also potentially
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make better use of a wide superscalar processor, as can bigger primitives like
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<code>mpn_addmul_2</code> or <code>mpn_addmul_4</code>.
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</p>
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<p>The restrictions on overlaps between sources and destinations
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(see <a href="Low_002dlevel-Functions.html#Low_002dlevel-Functions">Low-level Functions</a>) are designed to facilitate a variety of
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implementations. For example, knowing <code>mpn_add_n</code> won’t have partly
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overlapping sources and destination means reading can be done far ahead of
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writing on superscalar processors, and loops can be vectorized on a vector
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processor, depending on the carry handling.
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</p>
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</body>
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</html>
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