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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - shr <reg>, 1 sets flags in useful ways"
href="https://bugs.llvm.org/show_bug.cgi?id=33898">33898</a>
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<th>Summary</th>
<td>shr <reg>, 1 sets flags in useful ways
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>rjmccall@apple.com
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</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>"shr <reg>, 1" sets:
ZF if (<reg> >> 1) == 0, i.e. if (<reg> & ~1) == 0
CF if (<reg> & 1) == 1
A branch predicated on (x == 0 || x == 1), ((x & ~1) == 0), or (x ULE 1) can be
emitted as shr x, 1; jz.
A branch predicated on ((x & 1) == 1) can be emitted as shr x, 1; jb. This is
not useful on its own because test x, 1 exists, but it can be combined:
A branch predicated on (x == 0 || (x & 1) == 1) can be emitted as shr x, 1;
jbe.</pre>
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