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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - loop vectorizer fails to optimize dot product"
href="http://llvm.org/bugs/show_bug.cgi?id=22526">22526</a>
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<th>Summary</th>
<td>loop vectorizer fails to optimize dot product
</td>
</tr>
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<th>Product</th>
<td>new-bugs
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>Other
</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>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</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>ralph.campbell@broadcom.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>clang fails to optimize what looks like a very simple loop to me.
(run on ARM "Juno" box running Fedora 22 and using gcc 4.9.2 to compile llvm)
$ cat test.c
float foo(float *b, float *c) {
int i;
float v = 0.0;
for(i = 0; i < 1000; i++) {
v += b[i] + c[i];
}
return v;
}
$ clang -S -O3 -Rpass-analysis=loop-vectorize test.c
test.c:8:1: remark: loop not vectorized: value that could not be identified as
reduction is used outside the loop [-Rpass-analysis=loop-vectorize]
}
^
test.c:8:1: note: could not determine the original source location for :0:0</pre>
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