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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 - Missed BLSR for x == (x & -x) && x"
href="https://bugs.llvm.org/show_bug.cgi?id=42314">42314</a>
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<th>Summary</th>
<td>Missed BLSR for x == (x & -x) && x
</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>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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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>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
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<p>
<div>
<pre>bool blsr (int x)
{
return x == (x & -x) && x;
}
Trunk -O3 -march=haswell
blsr(int):
mov eax, edi
neg eax
setb cl
andn eax, eax, edi
sete al
and al, cl
ret
GCC -O3 -march=haswell
blsr(int):
blsr eax, edi
sete al
test edi, edi
setne dl
and eax, edx
ret</pre>
</div>
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