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<base href="http://llvm.org/bugs/" />
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<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - wrong code at -O2 and -O3 (vectorizer bug?)"
href="http://llvm.org/bugs/show_bug.cgi?id=17532">17532</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code at -O2 and -O3 (vectorizer bug?)
</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 at -O2 and -O3
(and clang 3.3 at -O3) on x86_64-linux-gnu in both 32-bit and 64-bit modes.
This is a regression from clang 3.2, and disappears with -fno-vectorize.
$ clang-trunk -v
clang version 3.4 (trunk 192279)
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 -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 -O3 small.c; a.out
1
$ clang-3.3 -O2 small.c; a.out
0
$ clang-3.2 -O2 small.c; a.out
0
$ clang-3.2 -O3 small.c; a.out
0
$
$ clang-trunk -O2 -fno-vectorize small.c; a.out
0
$ gcc-trunk -O2 small.c; a.out
0
$
---------------------------------------
int printf (const char *, ...);
int *a, *f, b = 1, e = 1;
static int **c = &a;
char d;
int
main ()
{
int **g = &a;
*c = &b;
f = *g;
int *h = f;
char *i = &d;
lbl:
--*i;
*h &= 1 % e;
if (d)
goto lbl;
printf ("%d\n", b);
return 0;
}</pre>
</div>
</p>
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