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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - LLVM cannot vectorize short reduction loop."
href="https://llvm.org/bugs/show_bug.cgi?id=25748">25748</a>
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<th>Summary</th>
<td>LLVM cannot vectorize short reduction loop.
</td>
</tr>
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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>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Loop Optimizer
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>congh@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>LLVM fails to vectoize the following reduction loop. The loop is unrolled
before reaching loop vectorizer, and the SLP vectorizer cannot vectorize it.
int a[32];
int reduce_add() {
int s = 0;
for (int i = 0; i < 32; ++i)
s = s + a[i];
return s;
}</pre>
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