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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - asan conflicts with gvn"
href="https://llvm.org/bugs/show_bug.cgi?id=25550">25550</a>
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<th>Summary</th>
<td>asan conflicts with gvn
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<tr>
<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>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>new bugs
</td>
</tr>
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<th>Assignee</th>
<td>kcc@google.com
</td>
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<th>Reporter</th>
<td>kcc@google.com
</td>
</tr>
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<th>CC</th>
<td>aizatsky@chromium.org, llvm-bugs@lists.llvm.org, stark@mit.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>[initially reported by Greg Stark:
<a href="http://lists.llvm.org/pipermail/llvm-dev/2015-November/092484.html">http://lists.llvm.org/pipermail/llvm-dev/2015-November/092484.html</a>]
Reproducer:
typedef union {
short q;
struct {
short x;
short y;
int for_alignment;
} w;
} U;
int main() {
char *buf = new char[2];
buf[0] = buf[1] = 0x0;
U *u = (U *)buf;
return u->q == 0 ? 0 : u->w.y;
}
gvn will speculatively combine two 2-byte loads into one,
thus moving one of the loads outside of the conditional pass.
We've seen these problems in the past, and have at least two guards against
those:
lib/Analysis/MemoryDependenceAnalysis.cpp:
Attribute::SanitizeAddress))
lib/Analysis/ValueTracking.cpp: Attribute::SanitizeAddress))
but none of these two help here.</pre>
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