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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - LLVM12 PCH leads to 2x slower compilation times"
href="https://bugs.llvm.org/show_bug.cgi?id=50294">50294</a>
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<th>Summary</th>
<td>LLVM12 PCH leads to 2x slower compilation times
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>12.0
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>-New Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>diaconitagabriel@gmail.com
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Starting with LLVM12, we are getting a 1.5x - 2x performance hit if we compile
our projects using PCH, compared to without PCH with LLVM 12. Exactly the
opposite of what one would expect by using precompiled headers.
Compared to LLVM 11, with PCH enabled, we are observing a penalty of 3-4x.</pre>
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