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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 - Optimization flag -O2 gives wrong results for SSE2 and AVX intrinsics"
href="https://bugs.llvm.org/show_bug.cgi?id=32391">32391</a>
</td>
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<th>Summary</th>
<td>Optimization flag -O2 gives wrong results for SSE2 and AVX intrinsics
</td>
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<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>PC
</td>
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<th>OS</th>
<td>Linux
</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>-New Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>daniel.arndt@iwr.uni-heidelberg.de
</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=18152" name="attach_18152" title="Failing test case">attachment 18152</a> <a href="attachment.cgi?id=18152&action=edit" title="Failing test case">[details]</a></span>
Failing test case
The attached code in 'symmetric_tensor_39_reduced.cc' gives wrong output if
optimization flags are used.
The expected output is
B[0][0][0]: 6
B[0][0][1]: 7
B[0][1][0]: 6
B[0][1][1]: 7
B[0][2][0]: 0
B[0][2][1]: 0
B[1][0][0]: 6
B[1][0][1]: 7
B[1][1][0]: 6
B[1][1][1]: 7
B[1][2][0]: 0
B[1][2][1]: 0
B[2][0][0]: 0
B[2][0][1]: 0
B[2][1][0]: 0
B[2][1][1]: 0
B[2][2][0]: 6
B[2][2][1]: 7
while the failing output is
B[0][0][0]: 0
B[0][0][1]: 0
B[0][1][0]: 0
B[0][1][1]: 0
B[0][2][0]: 0
B[0][2][1]: 0
B[1][0][0]: 0
B[1][0][1]: 0
B[1][1][0]: 0
B[1][1][1]: 0
B[1][2][0]: 0
B[1][2][1]: 0
B[2][0][0]: 0
B[2][0][1]: 0
B[2][1][0]: 0
B[2][1][1]: 0
B[2][2][0]: 0
B[2][2][1]: 0
It fails with -O2 for
-clang version 5.0.0 (trunk 295600)
-clang 4.0.0 rc2
-clang 3.9.1
-clang 3.7.1
-clang 3.6.0
while working with -O1 and -O3.
Fails on
-clang 3.5.0 with -O2 and -O3
-clang 3.4 with -O2 and -O3
while working with -O1
Works for -O1, -O2 and -O3 on
-clang 3.8.1
-clang 3.3
-clang 3.2
-clang 3.1
If
SymmetricTensor<4,dim,VectorizedArray> I;
SymmetricTensor<2,dim,VectorizedArray> A;
SymmetricTensor<2,dim,VectorizedArray> B;
is changed to
SymmetricTensor<4,dim,double> I;
SymmetricTensor<2,dim,double> A;
SymmetricTensor<2,dim,double> B;
and the loops over v are omitted (symmetric_tensor_39_double.cc), the output is
the same for -O1, -O2 and -O3 on clang-4.0.0rc2. Hence, it seems related to
vector intrinsics.
If A is filled in a separate function, there is no difference as well.
Some detective work can also be found at
<a href="https://github.com/dealii/dealii/pull/4058">https://github.com/dealii/dealii/pull/4058</a>.</pre>
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