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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 -Os in 64-bit mode (affecting all clang versions on x86_64-linux-gnu and MacOS X)"
href="http://llvm.org/bugs/show_bug.cgi?id=17504">17504</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code at -Os in 64-bit mode (affecting all clang versions on x86_64-linux-gnu and MacOS X)
</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 the current clang trunk and older versions
on x86_64-linux-gnu at -Os in 64-bit mode (but not 32-bit mode).
It also affects MacOS X.
I had hoped to reduce the testcase further, but it's the best I've been able to
get so far.
$ clang-trunk -v
clang version 3.4 (trunk 192089)
Target: x86_64-pc-linux-gnu
Thread model: posix
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/4.6.3
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
$
$ clang-trunk -O1 small.c; a.out
-46
$ clang-trunk -O2 small.c; a.out
-46
$ clang-trunk -Os small.c; a.out
-44
$ clang-3.3 -Os small.c; a.out
-44
$ clang-3.2 -Os small.c; a.out
-44
$ clang-3.1 -Os small.c; a.out
-44
$ clang-3.0 -Os small.c; a.out
-44
$ gcc-trunk -Os small.c; a.out
-46
$
----------------------------------
int printf (const char *, ...);
struct S
{
int f0;
int f3;
int f6;
int f7;
int f8;
};
int a;
static struct S b;
char
fn1 (char p1, char p2)
{
return p1 + p2;
}
void
fn3 (struct S p1)
{
}
int
fn4 ()
{
a--;
return 0;
}
static int
fn2 ()
{
char c = 117;
b.f0 = 0;
for (; b.f0 < 44; b.f0 = fn1 (b.f0, 4))
{
fn3 (b);
a--;
c++;
c && fn4 ();
}
a--;
return 0;
}
int
main ()
{
a = b.f3;
fn2 ();
fn2 ();
printf ("%d\n", a);
return 0;
}</pre>
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