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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Failure to optimize loop of and by progressively bigger operand to single and+select"
href="https://bugs.llvm.org/show_bug.cgi?id=50545">50545</a>
</td>
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<th>Summary</th>
<td>Failure to optimize loop of and by progressively bigger operand to single and+select
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Loop Optimizer
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>gabravier@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>int f(int c)
{
int i = 1;
while ((c & i)) {
c &= i;
i <<= 1;
}
return c;
}
This can be optimized to `return (c & 1) == 0 ? c : (c & 1);`. This
transformation is done by GCC, but not by LLVM.
Godbolt comparison: <a href="https://godbolt.org/z/oTxbxv5fo">https://godbolt.org/z/oTxbxv5fo</a>
alive2 comparison: <a href="https://alive2.llvm.org/ce/z/oDxuS4">https://alive2.llvm.org/ce/z/oDxuS4</a></pre>
</div>
</p>
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