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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Wrong mask generated for _mm_blendv_epi8"
href="https://llvm.org/bugs/show_bug.cgi?id=24532">24532</a>
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<th>Summary</th>
<td>Wrong mask generated for _mm_blendv_epi8
</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
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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
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>aivchenk@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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<pre>Created <span class=""><a href="attachment.cgi?id=14754" name="attach_14754" title="Reprocuder">attachment 14754</a> <a href="attachment.cgi?id=14754&action=edit" title="Reprocuder">[details]</a></span>
Reprocuder
Following code works with gcc and clang -O0, but fails on clang -O1:
_mm_blendv_epi8 produces wrong result in that case.
<span class="quote">>gcc ../blend.cpp -msse4.2 -O2 -o gcc.exe ; ./gcc.exe</span >
finish blend testing
<span class="quote">>clang++ ../blend.cpp -msse4.2 -O0; ./a.out</span >
finish blend testing
<span class="quote">>clang++ ../blend.cpp -msse4.2 -O1; ./a.out</span >
Aborted (core dumped)
I tested trunk so far only, but I suspect the issue affects 3.6 as well.
The problem is with wrong mask generated for pblendvb:
movdqa (%rsi), %xmm1
movaps .LCPI0_0(%rip), %xmm0 # xmm0 =
[0,0,0,255,0,0,0,255,255,255,255,255,255,255,255,255]
pblendvb (%rdx), %xmm1
movdqa %xmm1, (%rdi)
While the actual mask for the intrinsic was 0xff00000000000000ff000000ff000000</pre>
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