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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - NULL deref crash with -value-tracking-dom-conditions"
href="https://llvm.org/bugs/show_bug.cgi?id=24866">24866</a>
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<tr>
<th>Summary</th>
<td>NULL deref crash with -value-tracking-dom-conditions
</td>
</tr>
<tr>
<th>Product</th>
<td>tools
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Windows NT
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>opt
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>filtered+llvm-bugzilla@psychosanity.com
</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=14897" name="attach_14897" title="bugpoint-reduced testcase">attachment 14897</a> <a href="attachment.cgi?id=14897&action=edit" title="bugpoint-reduced testcase">[details]</a></span>
bugpoint-reduced testcase
While looking at some code somebody posted as an example where clang produces
significantly worse code than gcc[1] , I came across this crash while trying to
see if various command-line options could remedy the situation.
The attached bugpoint-reduced testcase demonstrates the problem when run with:
opt bugpoint-reduced-simplified.bc -value-tracking-dom-conditions -licm
-load-combine
The problem seems to be that the expression "Q.DT->getNode(Current)" (on line
640 in llvm\lib\Analysis\ValueTracking.cpp) is returning NULL, and is then
immediately dereferenced to call "->getIDom()". Why that is or how it should be
handled, I have no idea.
[1] The performance bug is filed at <a class="bz_bug_link
bz_status_NEW "
title="NEW --- - GCC4.9.2 optimizer produces 20% faster code than clang clang-600.0.56 (Xcode 6.1.1)"
href="show_bug.cgi?id=21760">https://llvm.org/bugs/show_bug.cgi?id=21760</a></pre>
</div>
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