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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - clang -O3 and loops result in garbage value"
href="http://llvm.org/bugs/show_bug.cgi?id=15920">15920</a>
</td>
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<th>Summary</th>
<td>clang -O3 and loops result in garbage value
</td>
</tr>
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<th>Product</th>
<td>clang
</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>Linux
</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>LLVM Codegen
</td>
</tr>
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<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>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The testcase below produces random output when compiled at -O3 with current
clang trunk (-O2 or below is fine). Perhaps a bad interaction with the loop
optimizer?
$ clang -v
clang version 3.3 (trunk 181189)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang -O2 test.c
$ ./a.out
1
$ clang -O3 test.c
$ ./a.out
2130055448
$
---------------------------
int printf(const char *, ...);
signed char c, d;
int i;
int
main ()
{
for (c = 0; c > -16; --c)
{
int *j = &i;
*j = 1;
for (d = 0; d; d = d + 0)
*j = 0;
}
printf ("%d\n", i);
return 0;
}</pre>
</div>
</p>
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