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| Next: <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> [<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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| <h4 class="subsubsection">9.53.3.1 Using Density Instructions</h4> |
| <a name="index-density-instructions"></a> |
| |
| <p>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 |
| ‘<samp>--no-transform</samp>’ 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> |
| <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. |
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