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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 --- - wrong code at -O1 and above on x86_64-linux-gnu (affecting clang trunk, 3.3, and 3.2)"
href="http://llvm.org/bugs/show_bug.cgi?id=17827">17827</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code at -O1 and above on x86_64-linux-gnu (affecting clang trunk, 3.3, and 3.2)
</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>
<tr>
<th>OS</th>
<td>All
</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>su@cs.ucdavis.edu
</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 code is miscompiled by the current clang trunk (as well as clang
3.2 and 3.3) on x86_64-linux-gnu at -O1 and above in both 32-bit and 64-bit
modes.
It is a regression from clang 3.1.
$ clang-trunk -v
clang version 3.4 (trunk 194075)
Target: x86_64-pc-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.3
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
$
$ clang-trunk -O0 small.c; a.out
1
$ clang-3.1 -O1 small.c; a.out
1
$
$ clang-trunk -O1 small.c; a.out
0
$ clang-3.3 -O1 small.c; a.out
0
$ clang-3.2 -O1 small.c; a.out
0
$
$ gcc-trunk -O1 small.c; a.out
1
$ icc -O1 small.c; a.out
1
$
------------------------------------
int printf (const char *, ...);
struct S
{
int f0;
int:1;
int f1:8;
int f2;
} a;
int b;
void
foo (int p)
{
struct S c = a;
c.f1 = p & 190;
b = c.f1 < 1;
}
int
main ()
{
foo (174);
printf ("%d\n", b);
return 0;
}</pre>
</div>
</p>
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