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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 - Clang punts on vectorization and issues incorrect diagnostic"
href="https://bugs.llvm.org/show_bug.cgi?id=34125">34125</a>
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<th>Summary</th>
<td>Clang punts on vectorization and issues incorrect diagnostic
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>4.0
</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>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>-New Bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>jeff.science@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=18948" name="attach_18948" title="make command output">attachment 18948</a> <a href="attachment.cgi?id=18948&action=edit" title="make command output">[details]</a></span>
make command output
Clang claims the reason it does not vectorize star[45] is because the trip
count cannot be determined, but the trip count determination is identical in
star[123], which are vectorized.
./stencil_tbb.hpp:63:7: remark: loop not vectorized: could not determine number
of loop iterations [-Rpass-analysis]
for (auto j=r.cols().begin(); j!=r.cols().end(); ++j ) {
^
As best I can tell, the issue is that the loop bodies for star[45] are too
large. Functions with 12 or fewer terms are vectorized whereas those with 16
or more are not.</pre>
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