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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 (only in 64-bit mode and affecting all clang versions)"
href="http://llvm.org/bugs/show_bug.cgi?id=20494">20494</a>
</td>
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<tr>
<th>Summary</th>
<td>wrong code at -O2 and -O3 on x86_64-linux-gnu (only in 64-bit mode and affecting all clang versions)
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<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 also affects earlier clang versions (including at least 3.0 and later).
$ clang-trunk -v
clang version 3.6.0 (trunk 214258)
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
2
$ clang-trunk -m32 -O2 small.c; a.out
2
$
$ clang-trunk -m64 -O2 small.c; a.out
-2147483647
$ clang-3.4 -m64 -O2 small.c; a.out
-2147483647
$ clang-3.3 -m64 -O2 small.c; a.out
-2147483647
$
---------------------------------
int printf (const char *, ...);
int a, h;
volatile int c;
short b, g[2];
char d, e;
long f;
int
fn1 (unsigned int p)
{
int i;
for (i = 0; i < 1; i++)
for (e = 1; e; e++)
{
d = p % 3;
c;
}
return p;
}
int
main ()
{
for (h = 0; h < 2; h++)
g[h] = -8;
f = a && 1;
b = fn1 (g[0] ^ f);
printf ("%d\n", d);
return 0;
}</pre>
</div>
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