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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 by LTO at -O1, -Os, and -O2 on x86_64-linux-gnu (affecting 3.4 and trunk in 64-bit mode)"
href="http://llvm.org/bugs/show_bug.cgi?id=20237">20237</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code by LTO at -O1, -Os, and -O2 on x86_64-linux-gnu (affecting 3.4 and trunk 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 and 3.4 miscompile the following code when using LTO at
-O1, Os, and -O2 on x86_64-linux-gnu in 64-bit mode (but not in 32-bit mode).
This is regression from 3.3.
$ clang-trunk -v
clang version 3.5.0 (trunk 212424)
Target: x86_64-unknown-linux-gnu
Thread model: posix
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 -O1 small.c; a.out
1
$ clang-trunk -flto -m32 -O1 small.c; a.out
1
$ clang-3.3 -flto -m64 -O1 small.c; a.out
1
$
$ clang-trunk -flto -m64 -O1 small.c; a.out
0
$ clang-3.4 -flto -m64 -O1 small.c; a.out
0
$
-------------------------------
int printf (const char *, ...);
int a, b, d, e, g, i;
struct S0
{
int f0;
int f1;
} c;
struct S1
{
int f0;
} f, h = {1};
int
fn1 (struct S0 p1)
{
return p1.f0;
}
void
fn2 (int p1, struct S1 p2)
{
int j = e;
for (e = 1; e; e = j)
{
if (c.f1)
b = 0;
else
{
i = 1 >> a;
if (!i)
fn2 (0, f);
b = p2.f0 || p1 | d;
}
p2 = h;
}
}
int
main ()
{
g = fn1 (c);
if (!g)
for (; c.f1; --c.f1);
fn2 (1, f);
printf ("%d\n", b);
return 0;
}</pre>
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