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<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - wrong code (FP exception) at -O3 on x86_64-linux-gnu (affecting 3.4.1 and later)"
href="http://llvm.org/bugs/show_bug.cgi?id=20856">20856</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code (FP exception) at -O3 on x86_64-linux-gnu (affecting 3.4.1 and later)
</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 -O3 on
x86_64-linux-gnu (in both 32-bit and 64-bit modes).
This is a regression from 3.4.
$ clang-trunk -v
clang version 3.6.0 (trunk 216814)
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 -O2 small.c; a.out
$ clang-3.4 -O3 small.c; a.out
$
$ clang-trunk -O3 small.c
$ ./a.out
Floating point exception (core dumped)
$
---------------------------------
int a, b, *d, g, i, **j;
short *f;
static char c;
struct
{
int f2;
} e;
void
fn1 (char *p)
{
i = a / *p;
}
void
fn2 (int p)
{
short h;
fn1 (&c);
f = &h;
for (; g < 1; g++)
if (c && p)
*j = 0;
}
void
fn3 (int *p)
{
fn2 (*p);
}
void
fn4 ()
{
b = 0;
for (c = -7; c; c++)
{
fn3 (&b);
for (; e.f2;)
*d = 0;
}
}
int
main ()
{
fn4 ();
return 0;
}</pre>
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