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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Huge codegen performance regression for Windows targets since LLVM 12, incl. latest 13-rc2"
href="https://bugs.llvm.org/show_bug.cgi?id=51827">51827</a>
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<th>Summary</th>
<td>Huge codegen performance regression for Windows targets since LLVM 12, incl. latest 13-rc2
</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>Windows NT
</td>
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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>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
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<th>Reporter</th>
<td>kinke@gmx.net
</td>
</tr>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=25252" name="attach_25252" title="xz-compressed bitcode input file">attachment 25252</a> <a href="attachment.cgi?id=25252&action=edit" title="xz-compressed bitcode input file">[details]</a></span>
xz-compressed bitcode input file
I'm seeing a codegen slowdown by about 2 orders of magnitude for the attached
.bc file (generated by LDC, the LLVM D compiler) starting with LLVM 12.0.0.
Seems to be specific to Windows/MSVC targets, and timings are back to normal
when enabling the optimizer.
Using clang from the official LLVM Windows builds from GitHub and compiling via
`clang -c template9.bc`:
* v11.0.1: ~2.4 seconds
* v12.0.1: ~246 seconds
* v13.0.0-rc2: ~227 seconds
Enabling the optimizer by adding `-O3` hints at a further little regression in
v13:
* v11.0.1: ~3.3 seconds
* v12.0.1: ~3.3 seconds
* v13.0.0-rc2: ~5.0 seconds</pre>
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