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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - SROA may create redundant PHI nodes"
href="https://llvm.org/bugs/show_bug.cgi?id=26376">26376</a>
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<th>Summary</th>
<td>SROA may create redundant PHI nodes
</td>
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<th>Product</th>
<td>new-bugs
</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>All
</td>
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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
</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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<th>Reporter</th>
<td>andrew.kaylor@intel.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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</tr>
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=15755" name="attach_15755" title="test case">attachment 15755</a> <a href="attachment.cgi?id=15755&action=edit" title="test case">[details]</a></span>
test case
I've come across a situation where SROA will create redundant PHI nodes while
promoting an alloca. The old SSAUpdater (optional prior to r246028) was able
to detect the redundancy in this case and avoid it. The PromoteRegToMem class
does not detect the redundancy.
I have seen a case (on 32-bit x86) where this led to an extra select and
resulted in a measurable performance degradation.
The attached test case demonstrates the problem.</pre>
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