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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - GVNHoist illegally hoists div instruction"
href="https://llvm.org/bugs/show_bug.cgi?id=31729">31729</a>
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<th>Summary</th>
<td>GVNHoist illegally hoists div instruction
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<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>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>matze@braunis.de
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=17884" name="attach_17884" title="C reproducer">attachment 17884</a> <a href="attachment.cgi?id=17884&action=edit" title="C reproducer">[details]</a></span>
C reproducer
The attached testcase performs a division (by zero) before checking the
condition present in the original sourcecode. The problem appears when
compiling test-suite/SingleSource/UnitTests/SignlessTypes/rem.c with the -Oz
flag.
I reduced the test to a small reproducer and will attach them here. Looking at
the -print-after-all output it seems GVNHoist is to blame and the problem goes
away with -gvn-max-hoisted=0 for me.
I can reproduce this on a macOS system with:
$ clang -Oz reduced.c
$ ./a.out
Floating point exception: 8
I attached a -O0 -emit-llvm .ll file for convenience but did not test whether
that reproduces as well.</pre>
</div>
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