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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Compile time regression introduced in r322401"
href="https://bugs.llvm.org/show_bug.cgi?id=38088">38088</a>
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<th>Summary</th>
<td>Compile time regression introduced in r322401
</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
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<th>Reporter</th>
<td>alex@crichton.co
</td>
</tr>
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<th>CC</th>
<td>brzycki@gmail.com, llvm-bugs@lists.llvm.org
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</tr></table>
<p>
<div>
<pre>We're currently attempting to upgrade LLVM in the Rust project [1] but we're
unfortunately losing performance from this upgrade on a number of our
benchmarks [2]. I've been doing some bisection and it's somewhat difficult to
narrow down on any one regression because the regression to track down is
smaller and smaller.
In any case though I've tracked down one regression to r322401 or
<a href="https://reviews.llvm.org/D40146">https://reviews.llvm.org/D40146</a>. The IR file [3] takes awhile to pass through
the `opt` tool, but before this commit it took 16.8s locally and afterwards it
takes 17.9.
I haven't dove too much further into the patch, but let me know if I can help
out!
[1]: <a href="https://github.com/rust-lang/rust/pull/51966">https://github.com/rust-lang/rust/pull/51966</a>
[2]:
<a href="https://perf.rust-lang.org/compare.html?start=478226cc2ab768d45cc8284652c5997559b7b05f&end=cde23ec54231f5454f8c128383fe9962b9e598b0">https://perf.rust-lang.org/compare.html?start=478226cc2ab768d45cc8284652c5997559b7b05f&end=cde23ec54231f5454f8c128383fe9962b9e598b0</a>
[3]: <a href="https://gist.github.com/alexcrichton/fda0ea23be40b34f9927840179a82e93">https://gist.github.com/alexcrichton/fda0ea23be40b34f9927840179a82e93</a></pre>
</div>
</p>
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