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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - eb0e1978df7b9e7 caused msan false positive in vectorized crc code"
href="https://bugs.llvm.org/show_bug.cgi?id=44652">44652</a>
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<th>Summary</th>
<td>eb0e1978df7b9e7 caused msan false positive in vectorized crc code
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>nicolasweber@gmx.de
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=23056" name="attach_23056" title="crc_folding.c standalone repro">attachment 23056</a> <a href="attachment.cgi?id=23056&action=edit" title="crc_folding.c standalone repro">[details]</a></span>
crc_folding.c standalone repro
This is very similar to issue 42982, but in slightly different vectorized crc
code in zlib.
As far as I can tell, no uninitialized reads happen here, and things are happy
before eb0e1978df7b9e7
bin/clang crc_folding.c -msse4.2 -mpclmul -g -O2 -fsanitize=memory && ./a.out
==135688==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x499549 in crc_fold_512to32
/usr/local/google/home/thakis/src/chrome/src/crc_folding.c:479:16
#1 0x499549 in main
/usr/local/google/home/thakis/src/chrome/src/crc_folding.c:514:10
#2 0x7f706ab6f52a in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x2352a)
#3 0x41f269 in _start
(/usr/local/google/home/thakis/src/chrome/src/a.out+0x41f269)
SUMMARY: MemorySanitizer: use-of-uninitialized-value
/usr/local/google/home/thakis/src/chrome/src/crc_folding.c:479:16 in
crc_fold_512to32
(reduced from <a href="https://crbug.com/1045291">https://crbug.com/1045291</a>)</pre>
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