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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 optimization levels -Os and above"
href="http://llvm.org/bugs/show_bug.cgi?id=16462">16462</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code at optimization levels -Os and above
</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 current clang trunk and 3.3 on
x86_64-linux-gnu at -Os and above (in both 32-bit and 64-bit modes). This is a
regression from 3.2.
$ clang-trunk -v
clang version 3.4 (trunk 184829)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang-trunk -O1 reduced.c
$ a.out
1
$ clang-trunk -Os reduced.c
$ a.out
0
$ clang-3.3 -Os reduced.c
$ a.out
0
$ clang-3.2 -Os reduced.c
$ a.out
1
$
-----------------------------------------------
int printf (const char *, ...);
static short fn1 (int p)
{
return p ? 0 : 1;
}
unsigned short fn2 (int p)
{
return -p;
}
int a[1], b, *c = &b, d;
void fn3 ()
{
int *t = &d;
if (fn2(1) >= fn1 (t == &a[0]))
*c = 1;
}
int main ()
{
fn3 ();
printf ("%d\n", b);
return 0;
}</pre>
</div>
</p>
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