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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - performance regression caused by e6a7e3b5e3e779a3bfb617c8d9ed4302edab2cef"
href="https://bugs.llvm.org/show_bug.cgi?id=45263">45263</a>
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<th>Summary</th>
<td>performance regression caused by e6a7e3b5e3e779a3bfb617c8d9ed4302edab2cef
</td>
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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
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>release blocker
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>wmi@google.com
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<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
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<pre>We found the commit below causing 10% performance regression in one of our
benchmark:
<a href="https://github.com/llvm/llvm-project/commit/e6a7e3b5e3e779a3bfb617c8d9ed4302edab2cef">https://github.com/llvm/llvm-project/commit/e6a7e3b5e3e779a3bfb617c8d9ed4302edab2cef</a>
I extracted a testcase 1.cc and attached it.
clang.1 -O3 -fexperimental-new-pass-manager -std=gnu++17 -msse4.1 1.cc -S -o
1.s
clang.2 -O3 -fexperimental-new-pass-manager -std=gnu++17 -msse4.1 1.cc -S -o
2.s
clang.1 was built at the version just before
e6a7e3b5e3e779a3bfb617c8d9ed4302edab2cef. clang.2 was built at
e6a7e3b5e3e779a3bfb617c8d9ed4302edab2cef. Searching the loop "This Inner Loop
Header: Depth=2". 1.s has 65 instructions in the loop. 2.s has 72 instructions.</pre>
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