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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Optimized and unoptimized version of the clang-built program behave differently"
href="https://bugs.llvm.org/show_bug.cgi?id=43038">43038</a>
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<th>Summary</th>
<td>Optimized and unoptimized version of the clang-built program behave differently
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>8.0
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>FreeBSD
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++11
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>yuri@tsoft.com
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>Created <span class=""><a href="attachment.cgi?id=22387" name="attach_22387" title="testcase">attachment 22387</a> <a href="attachment.cgi?id=22387&action=edit" title="testcase">[details]</a></span>
testcase
The attached testcase's behavior is different when it is built with -O2 and
without -O2.
With -O2 it fails with this Eigen exception:
<span class="quote">> Assertion failed: (lhs.cols() == rhs.rows() && "invalid matrix product" && "if you wanted a coeff-wise or a dot product use the respective explicit functions"), function Product, file /usr/local/include/eigen3/Eigen/src/Core/Product.h, line 97.
> Abort trap</span >
Without -O2 it doesn't print the exception and succeeds.
The line labeled with "// BUG" seems to be related.
It produces some Eigen-specific type
(N5Eigen7ProductINS_6MatrixIdLin1ELin1ELi0ELin1ELin1EEES2_Li0EEE) in place of
"auto" that later crashes with -O2.
If this "auto" is replaced with "M" (regular matrix) - it doesn't crash with
-O2.
While looking at this code, I can't tell why does it fail conditionally on -O2
like this. Nothing there alters that matrix, or any arguments of that
multiplication.
Optimization level should not trigger changes of behavior like this, especially
additional asserts.
clang-8 and clang-9 on FreeBSD 12 amd64.</pre>
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