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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 in 64-bit mode"
href="http://llvm.org/bugs/show_bug.cgi?id=21741">21741</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code at -O2 and -O3 on x86_64-linux-gnu in 64-bit mode
</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>-New Bugs
</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 current clang trunk miscompiles the following code at -O2 and -O3 on
x86_64-linux-gnu in 64-bit mode (but not in 32-bit mode).
This is a regression from 3.5.0.
$ clang-trunk -v
clang version 3.6.0 (trunk 223263)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8.1
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/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.1
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
$
$ clang-trunk -m64 -Os small.c; a.out
$ clang-trunk -m32 -O2 small.c; a.out
$ clang-3.5.0 -m64 -O2 small.c; a.out
$
$ clang-trunk -m64 -O2 small.c
$ a.out
Segmentation fault (core dumped)
$
-----------------------------------
int a, b, c, d, e, h, k[4], l, n;
char f, m, g[3][5];
void
fn1 ()
{
for (f = 2; f >= 0; f--)
{
k[f + d] = 0;
for (h = 0; h < 2; h++)
{
for (; e < 2; e++)
m = a;
l = g[f][d + 1] & a & 1;
n = k[0] >= 0 ? 1 : 1 >> b;
if (n)
break;
for (c = 0; c < 1; c++)
d = -5000000;
}
}
}
int
main ()
{
fn1 ();
return 0;
}</pre>
</div>
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