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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - SIMD code with -O2"
href="https://llvm.org/bugs/show_bug.cgi?id=27833">27833</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>SIMD code with -O2
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>MacOS X
</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>kazunori.ueda.ku@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=16396" name="attach_16396" title="v2d2.i and related source files">attachment 16396</a> <a href="attachment.cgi?id=16396&action=edit" title="v2d2.i and related source files">[details]</a></span>
v2d2.i and related source files
The enclosed program, compiled with clang -m32 -O2 *.i, produces a strange
output
0x7b06e5ed, 0x7b06e44f, 0x7b06e5f5, 0x7b06e42f
0x7b06e5f5, 0x7b06e42f, 0x0, 0x0
segmentation fault: 11
from two successive printf statements in v2d2.i:
printf("%p, %p, %p, %p\n",
allocp[116], allocp[117], allocp[118], allocp[119]);
x59 = ((q)((unsigned long)(&allocp[118]) + 0x1));
printf("%p, %p, %p, %p\n",
allocp[116], allocp[117], allocp[118], allocp[119]);
while clang -m32 -O1 *.i produces an expected output
0x7c2d81ed, 0x7c2d804f, 0x7c2d81f5, 0x7c2d802f
0x7c2d81ed, 0x7c2d804f, 0x7c2d81f5, 0x7c2d802f
I look into the assembly code of v2d2.c and found that -O2 uses SIMD
instructions while -O1 doesn't.
FYI, v2d2.c is a simplified version of a machine-generated program from our
compiler, and all the other .c files are just to make v2d2.c run.</pre>
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