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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - X86 bugs in extract value and select"
href="https://bugs.llvm.org/show_bug.cgi?id=45995">45995</a>
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<th>Summary</th>
<td>X86 bugs in extract value and select
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</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
</td>
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<th>Component</th>
<td>new bugs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>ajcbik@google.com
</td>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>The method combineExtractVectorElt() in lib/Target/X86/X86ISelLowering.cpp
incorrectly combines the extract_vector_elt instructions that operate on
different results. For example, it is fine to combine
t0 = merge_values a0, a1, a2, a3
i1 = extract_vector_elt t0, Constant:i64<2>
i1 = extract_vector_elt t0, Constant:i64<3>
but not
i1 = extract_vector_elt t0:1, Constant:i64<2>
(note the :1), since it operates on a different result. As a result, a single
MOVMSK is shared, when there should be several.
While debugging the issue, I also found a but in combineSelect() in the same
file. The part that tries to deal with bitcasts did not properly test for an
actual machine value type.</pre>
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