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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - AVX2: wrong code generated by combining cross-lane permute with in-lane shuffle"
href="https://llvm.org/bugs/show_bug.cgi?id=25531">25531</a>
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<th>Summary</th>
<td>AVX2: wrong code generated by combining cross-lane permute with in-lane shuffle
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>tilkax@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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</tr></table>
<p>
<div>
<pre>#include <x86intrin.h>
__m256i foo(__m256i v)
{
v = _mm256_permute4x64_epi64(v, _MM_SHUFFLE(0, 1, 0, 0));
v = _mm256_shuffle_epi8(v, _mm256_setzero_si256());
return v;
}
This code is being lowered into a single vpshufb, which doesn't work because
vpshufb can't index across 128-bit lanes.
Could be fixed by partially reverting r230753 or by adding proper 256-bit
support to shuffle chain combining.</pre>
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