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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - program crashes at movaps, unaligned stack address, -O3"
href="https://bugs.llvm.org/show_bug.cgi?id=34038">34038</a>
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<th>Summary</th>
<td>program crashes at movaps, unaligned stack address, -O3
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>4.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>release blocker
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>eric@youngblut.net
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<pre>Created <span class=""><a href="attachment.cgi?id=18898" name="attach_18898" title="C program for repro">attachment 18898</a> <a href="attachment.cgi?id=18898&action=edit" title="C program for repro">[details]</a></span>
C program for repro
ericy@mrpink:~$ /usr/bin/clang --version
clang version 4.0.0-1ubuntu1 (tags/RELEASE_400/rc1)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
ericy@mrpink:~$ /usr/bin/clang -O3 movaps_unaligned_crash.c && ./a.out
Segmentation fault
It does not repro with -O2.
You can see that it used the movaps instruction with an unaligned address.
(gdb) disassemble
Dump of assembler code for function main:
0x0000000000400490 <+0>: sub $0x28,%rsp
0x0000000000400494 <+4>: movq $0x0,0x20(%rsp)
0x000000000040049d <+13>: movq $0x0,0x18(%rsp)
0x00000000004004a6 <+22>: mov 0x200b7b(%rip),%rax # 0x601028
<obj>
=> 0x00000000004004ad <+29>: movaps 0x18(%rsp),%xmm0
0x00000000004004b2 <+34>: movaps %xmm0,(%rsp)
0x00000000004004b6 <+38>: mov $0x601028,%edi
0x00000000004004bb <+43>: xor %esi,%esi
0x00000000004004bd <+45>: xor %edx,%edx
0x00000000004004bf <+47>: xor %ecx,%ecx
0x00000000004004c1 <+49>: xor %r8d,%r8d
0x00000000004004c4 <+52>: callq *(%rax)
0x00000000004004c6 <+54>: xor %eax,%eax
0x00000000004004c8 <+56>: add $0x28,%rsp
0x00000000004004cc <+60>: retq
End of assembler dump.
(gdb) p $rsp
$1 = (void *) 0x7fffffffdf50</pre>
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