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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - incorrect loop optimization at -O3"
href="http://llvm.org/bugs/show_bug.cgi?id=16058">16058</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>incorrect loop optimization at -O3
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>dhazeghi@yahoo.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following testcase is miscompiled by clang trunk at -O3 optimization level
on x86_64-linux-gnu, producing an executable that hangs. This occurs in both
32-bit and 64-bit mode.
$ clang-trunk -v
clang version 3.4 (trunk 182084)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang-trunk -O2 hang.c
$ ./a.out
$ clang-trunk -O3 hang.c
$ ./a.out
<hangs>
--------------------------------
int a, b, c, *p = &a;
static void
foo(int *l)
{
for (b = -28; b < 4; b++)
{
*l = 1;
for (c = 0; c; --c)
*l = 0;
}
label:
for (b = 0; b >= 0; --b)
{
if (*p)
continue;
goto label;
}
return;
}
int
main()
{
int *q = &a;
foo(q);
return 0;
}</pre>
</div>
</p>
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