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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Performance regression saw after https://reviews.llvm.org/rG9c4c2f24725e9f98b96fb360894276d342c3ba50"
href="https://bugs.llvm.org/show_bug.cgi?id=51149">51149</a>
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<th>Summary</th>
<td>Performance regression saw after https://reviews.llvm.org/rG9c4c2f24725e9f98b96fb360894276d342c3ba50
</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>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>wmi@google.com
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=25039" name="attach_25039" title="compare.png">attachment 25039</a> <a href="attachment.cgi?id=25039&action=edit" title="compare.png">[details]</a></span>
compare.png
We have an internal micro-benchmark seeing 11% performance regression after
<a href="https://reviews.llvm.org/rG9c4c2f24725e9f98b96fb360894276d342c3ba50">https://reviews.llvm.org/rG9c4c2f24725e9f98b96fb360894276d342c3ba50</a>.
We extract a testcase to show the problem:
clang-without-the-patch -fexperimental-new-pass-manager -O3 1.ll -S -o /tmp/1.s
clang-with-the-patch -fexperimental-new-pass-manager -O3 1.ll -S -o /tmp/2.s
1.ll, 1.s and 2.s are attached.
In the compare.png attached, for the same code region, we show there are 13
instructions in the 2.s while there are 10 instructions in the 1.s.</pre>
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