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toolchain-gcc-arm-embedded

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<a name="MMIX_002dExpand"></a>
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Next: <a href="MMIX_002dSyntax.html#MMIX_002dSyntax" accesskey="n" rel="next">MMIX-Syntax</a>, Previous: <a href="MMIX_002dOpts.html#MMIX_002dOpts" accesskey="p" rel="prev">MMIX-Opts</a>, Up: <a href="MMIX_002dDependent.html#MMIX_002dDependent" accesskey="u" rel="up">MMIX-Dependent</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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<a name="Instruction-expansion-1"></a>
<h4 class="subsection">9.28.2 Instruction expansion</h4>

<a name="index-instruction-expansion_002c-MMIX"></a>
<p>When <code>as</code> encounters an instruction with an operand that is
either not known or does not fit the operand size of the instruction,
<code>as</code> (and <code>ld</code>) will expand the instruction into
a sequence of instructions semantically equivalent to the operand fitting
the instruction.  Expansion will take place for the following
instructions:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>GETA</samp>&rsquo;</dt>
<dd><p>Expands to a sequence of four instructions: <code>SETL</code>, <code>INCML</code>,
<code>INCMH</code> and <code>INCH</code>.  The operand must be a multiple of four.
</p></dd>
<dt>Conditional branches</dt>
<dd><p>A branch instruction is turned into a branch with the complemented
condition and prediction bit over five instructions; four instructions
setting <code>$255</code> to the operand value, which like with <code>GETA</code> must
be a multiple of four, and a final <code>GO $255,$255,0</code>.
</p></dd>
<dt>&lsquo;<samp>PUSHJ</samp>&rsquo;</dt>
<dd><p>Similar to expansion for conditional branches; four instructions set
<code>$255</code> to the operand value, followed by a <code>PUSHGO $255,$255,0</code>.
</p></dd>
<dt>&lsquo;<samp>JMP</samp>&rsquo;</dt>
<dd><p>Similar to conditional branches and <code>PUSHJ</code>.  The final instruction
is <code>GO $255,$255,0</code>.
</p></dd>
</dl>

<p>The linker <code>ld</code> is expected to shrink these expansions for
code assembled with &lsquo;<samp>--relax</samp>&rsquo; (though not currently implemented).
</p>


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