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66Next: <a href="Xtensa-Automatic-Alignment.html#Xtensa-Automatic-Alignment" accesskey="n" rel="next">Xtensa Automatic Alignment</a>, Up: <a href="Xtensa-Optimizations.html#Xtensa-Optimizations" accesskey="u" rel="up">Xtensa Optimizations</a> &nbsp; [<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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70<h4 class="subsubsection">9.55.3.1 Using Density Instructions</h4>
71<a name="index-density-instructions"></a>
72
73<p>The Xtensa instruction set has a code density option that provides
7416-bit versions of some of the most commonly used opcodes.  Use of these
75opcodes can significantly reduce code size.  When possible, the
76assembler automatically translates instructions from the core
77Xtensa instruction set into equivalent instructions from the Xtensa code
78density option.  This translation can be disabled by using underscore
79prefixes (see <a href="Xtensa-Opcodes.html#Xtensa-Opcodes">Opcode Names</a>), by using the
80&lsquo;<samp>--no-transform</samp>&rsquo; command-line option (see <a href="Xtensa-Options.html#Xtensa-Options">Command
81Line Options</a>), or by using the <code>no-transform</code> directive
82(see <a href="Transform-Directive.html#Transform-Directive">transform</a>).
83</p>
84<p>It is a good idea <em>not</em> to use the density instructions directly.
85The assembler will automatically select dense instructions where
86possible.  If you later need to use an Xtensa processor without the code
87density option, the same assembly code will then work without modification.
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