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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 -O1 and above on x86_64-linux-gnu in 32-bit mode (for code with the "pack" pragma and bitfields)"
href="http://llvm.org/bugs/show_bug.cgi?id=18862">18862</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>wrong code at -O1 and above on x86_64-linux-gnu in 32-bit mode (for code with the "pack" pragma and bitfields)
</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 following code is miscompiled by the current clang trunk at -O1 and above
in 32-bit mode (but not 64-bit) on x86_64-linux-gnu.
This is a regression from 3.4.
$ clang-trunk -v
clang version 3.5 (trunk 201494)
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 multiilb: .;@m64
Candidate multiilb: 32;@m32
Selected multilib: .;@m64
$
$ clang-trunk -m32 -O0 small.c; a.out
0
-2
$ clang-trunk -m64 -O1 small.c; a.out
0
-2
$ clang-3.4 -m32 -O1 small.c; a.out
0
-2
$
$ clang-trunk -m32 -O1 small.c; a.out
0
-1
$
--------------------------------
int printf (const char *, ...);
#pragma pack(1)
struct
{
int f0:9;
int f1:30;
int f2:5;
int f3:23;
int f4:11;
int f5:29;
int f6:24;
int:14;
} a, b = {0, 0, 0, 0, 0, 0, -2};
int c;
int
main ()
{
printf ("%d\n", a.f6);
for (; c < 1; c++)
printf ("%d\n", b.f6);
return 0;
}</pre>
</div>
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