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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 out low bits of result of left shift of constant"
href="https://bugs.llvm.org/show_bug.cgi?id=48984">48984</a>
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<th>Summary</th>
<td>Failure to optimize out low bits of result of left shift of constant
</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>
</tr>
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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>Scalar Optimizations
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>gabravier@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>int f(int a)
{
return ((2 << a) & 1) == 0;
}
This can be optimized to `return 1;`. This transformation is done by GCC, but
by LLVM.
Godbolt comparison here: <a href="https://godbolt.org/z/dTfsbx">https://godbolt.org/z/dTfsbx</a>
alive2 check here: <a href="https://alive2.llvm.org/ce/z/U3DMgJ">https://alive2.llvm.org/ce/z/U3DMgJ</a></pre>
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</p>
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