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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Clang Generates Incorrect Code With Certain Arch and Optimization Combinations"
href="http://llvm.org/bugs/show_bug.cgi?id=16834">16834</a>
</td>
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<th>Summary</th>
<td>Clang Generates Incorrect Code With Certain Arch and Optimization Combinations
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>Macintosh
</td>
</tr>
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<th>OS</th>
<td>MacOS X
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>LLVM Codegen
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>mathpup@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=11007" name="attach_11007" title="Test case">attachment 11007</a> <a href="attachment.cgi?id=11007&action=edit" title="Test case">[details]</a></span>
Test case
With the latest Clang/LLVM from SVN, the sample program abc.cpp produces
incorrect output when compiled with the optimization flags
-O3 -march=corei7-avx -fslp-vectorize -fslp-vectorize-aggressive
The problem goes away if -fslp-vectorize-aggressive is removed, and it also
goes away if -march=corei7-avx.
I am attaching sample C++ source for abc.cpp. I tried to narrow down this test
case, but this seems to be as simple as I can make it while sitting exhibiting
the problem. The sample program is based on code used in Qt 5 for working
with Bezier curves.
Correct output:
[10, 20], [30, 40], [50, 60], [70, 80]
[10, 20], [20, 30], [30, 40], [40, 50]
[40, 50], [50, 60], [60, 70], [70, 80]
Incorrect output produced as described above:
[10, 20], [30, 40], [50, 60], [70, 80]
[10, 20], [20, 30], [30, 40], [22.5, 50]
[22.5, 50], [45, 60], [60, 70], [70, 80]
I did attempt to use bugpoint, but I could not figure out how to produce any
output that seemed useful.</pre>
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