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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Performance regression on ARM within (219545, 219569]"
href="http://llvm.org/bugs/show_bug.cgi?id=21296">21296</a>
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<th>Summary</th>
<td>Performance regression on ARM within (219545, 219569]
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>new bugs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>renato.golin@linaro.org
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Our benchmark buildbot detected a regression on ARM:
<a href="http://llvm.org/perf/db_default/v4/nts/graph?plot.0=49.128.2&highlight_run=31861">http://llvm.org/perf/db_default/v4/nts/graph?plot.0=49.128.2&highlight_run=31861</a>
According to Hal:
Based on the commit logs, it does seem like the best candidates are:
r219566, r219567, r219568 - InstCombine bug fixes re: no-wrap flags
r219550, r219562 - Fixes to trip-count computations in the
vectorizer/unroller
and given the magnitude of the change, I think that the trip-count changes are
more likely.
Since those were bug fixes, we should proceed with caution and make sure there
isn't a fix on top of those patches before considering anything more radical.
It may very well be that the ARM back-end is not dealing with some new patterns
correctly, or that the transformation has generated unoptimal sequences.</pre>
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</p>
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