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<title>Xtensa Branch Relaxation - Using as</title>
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<a name="Xtensa-Branch-Relaxation"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Xtensa-Call-Relaxation.html#Xtensa-Call-Relaxation">Xtensa Call Relaxation</a>,
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Up: <a rel="up" accesskey="u" href="Xtensa-Relaxation.html#Xtensa-Relaxation">Xtensa Relaxation</a>
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<h5 class="subsubsection">9.52.4.1 Conditional Branch Relaxation</h5>
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<p><a name="index-relaxation-of-branch-instructions-2466"></a><a name="index-branch-instructions_002c-relaxation-2467"></a>
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When the target of a branch is too far away from the branch itself,
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i.e., when the offset from the branch to the target is too large to fit
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in the immediate field of the branch instruction, it may be necessary to
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replace the branch with a branch around a jump. For example,
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<pre class="smallexample"> beqz a2, L
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</pre>
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<p>may result in:
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<pre class="smallexample"> bnez.n a2, M
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j L
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M:
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</pre>
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<p>(The <code>BNEZ.N</code> instruction would be used in this example only if the
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density option is available. Otherwise, <code>BNEZ</code> would be used.)
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<p>This relaxation works well because the unconditional jump instruction
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has a much larger offset range than the various conditional branches.
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However, an error will occur if a branch target is beyond the range of a
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jump instruction. <samp><span class="command">as</span></samp> cannot relax unconditional jumps.
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Similarly, an error will occur if the original input contains an
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unconditional jump to a target that is out of range.
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<p>Branch relaxation is enabled by default. It can be disabled by using
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underscore prefixes (see <a href="Xtensa-Opcodes.html#Xtensa-Opcodes">Opcode Names</a>), the
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‘<samp><span class="samp">--no-transform</span></samp>’ command-line option (see <a href="Xtensa-Options.html#Xtensa-Options">Command Line Options</a>), or the <code>no-transform</code> directive
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(see <a href="Transform-Directive.html#Transform-Directive">transform</a>).
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