<html lang="en"> <head> <title>Density Instructions - 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="Xtensa-Optimizations.html#Xtensa-Optimizations" title="Xtensa Optimizations"> <link rel="next" href="Xtensa-Automatic-Alignment.html#Xtensa-Automatic-Alignment" title="Xtensa Automatic Alignment"> <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="Density-Instructions"></a>Next: <a rel="next" accesskey="n" href="Xtensa-Automatic-Alignment.html#Xtensa-Automatic-Alignment">Xtensa Automatic Alignment</a>, Up: <a rel="up" accesskey="u" href="Xtensa-Optimizations.html#Xtensa-Optimizations">Xtensa Optimizations</a> <hr><br> </div> <h5 class="subsubsection">9.36.3.1 Using Density Instructions</h5> <p><a name="index-density-instructions-1858"></a> The Xtensa instruction set has a code density option that provides 16-bit versions of some of the most commonly used opcodes. Use of these opcodes can significantly reduce code size. When possible, the assembler automatically translates instructions from the core Xtensa instruction set into equivalent instructions from the Xtensa code density option. This translation can be disabled by using underscore prefixes (see <a href="Xtensa-Opcodes.html#Xtensa-Opcodes">Opcode Names</a>), by using the <span class="samp">--no-transform</span> command-line option (see <a href="Xtensa-Options.html#Xtensa-Options">Command Line Options</a>), or by using the <code>no-transform</code> directive (see <a href="Transform-Directive.html#Transform-Directive">transform</a>). <p>It is a good idea <em>not</em> to use the density instructions directly. The assembler will automatically select dense instructions where possible. If you later need to use an Xtensa processor without the code density option, the same assembly code will then work without modification. </body></html>