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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Failure to optimize simple bitwise pattern"
href="https://bugs.llvm.org/show_bug.cgi?id=48524">48524</a>
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<tr>
<th>Summary</th>
<td>Failure to optimize simple bitwise pattern
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<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>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Scalar Optimizations
</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 f1(int n)
{
return n - (((n > 63) ? n : 63) & -64);
}
This can be optimized to `return (n <= 63) ? n : (n & 63);` (and presumably the
same optimization should be doable with other powers of 2).
PS: I found this optimization while looking at how this :
int f1(int n)
{
while (n >= 64)
n -= 64;
return n;
}
is optimized. LLVM outputs the first example I gave here, while GCC outputs the
optimization I gave here.</pre>
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