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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - wrong code at -O2 and -O3 on x86_64-linux-gnu (affecting clang trunk, 3.3, and 3.2)"
href="http://llvm.org/bugs/show_bug.cgi?id=17847">17847</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code at -O2 and -O3 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 and clang 3.3 at
-O2 and -O3 on x86_64-linux-gnu in both 32-bit and 64-bit modes.
It also affects clang 3.2 and 2.9 at -O3 (not at -O2), but neither clang 3.0
nor 3.1.
$ clang-trunk -v
clang version 3.4 (trunk 194255)
Target: x86_64-pc-linux-gnu
Thread model: posix
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 -Os small.c; a.out
0
$ clang-trunk -O2 small.c; a.out
1
$ clang-trunk -O3 small.c; a.out
1
$ clang-3.3 -O2 small.c; a.out
1
$ clang-3.3 -O3 small.c; a.out
1
$ clang-3.2 -O2 small.c; a.out
0
$ clang-3.2 -O3 small.c; a.out
1
$
$ gcc-trunk -O2 small.c; a.out
0
$
------------------------------------
int printf (const char *, ...);
int a = 1, b, c, d, e, g;
int
fn1 (int p1, int p2)
{
return p1 && p1 > 647 - p2 ? p1 : p1 + p2;
}
int
fn2 (char p1)
{
int f = 0;
for (; f < 36; f = fn1 (f, 8))
{
for (; c; c++);
if (f ^ 1)
{
if (e)
d = p1 ? 1 : 0;
else if (p1)
break;
b = p1-- == 0;
}
}
return f;
}
int
main ()
{
g = fn2 (64);
g || (a = 0);
printf ("%d\n", a);
return 0;
}</pre>
</div>
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