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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [X86][AVX] extract_subvector shuffle disaster"
href="http://llvm.org/bugs/show_bug.cgi?id=22359">22359</a>
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<th>Summary</th>
<td>[X86][AVX] extract_subvector shuffle disaster
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
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<th>Reporter</th>
<td>spatel+llvm@rotateright.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>This is a testcase I was considering using in a patch for <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [X86][AVX] separate stores are not being merged into a single 256bit store."
href="show_bug.cgi?id=21711">bug 21711</a>, but
something is causing the AVX1/AVX2 codegen to go wrong. This doesn't happen
with SSE.
We're trying to store half of a 256-bit vector here:
define void @f7(<8 x float> %v, <2 x float>* %ptr) {
%idx2 = getelementptr inbounds <2 x float>* %ptr, i64 1
%shuffle0 = shufflevector <8 x float> %v, <8 x float> undef, <2 x i32> <i32
0, i32 1>
%shuffle1 = shufflevector <8 x float> %v, <8 x float> undef, <2 x i32> <i32
2, i32 3>
store <2 x float> %shuffle0, <2 x float>* %ptr, align 8
store <2 x float> %shuffle1, <2 x float>* %idx2, align 8
ret void
}
$ ./llc extract.ll -mattr=sse -o -
...
movups %xmm0, (%rdi)
retq
$ ./llc extract.ll -mattr=avx -o -
...
vpermilps $231, %xmm0, %xmm1 ## xmm1 = xmm0[3,1,2,3]
vpermilpd $1, %xmm0, %xmm2 ## xmm2 = xmm0[1,0]
vmovshdup %xmm0, %xmm3 ## xmm3 = xmm0[1,1,3,3]
vinsertps $16, %xmm3, %xmm0, %xmm0 ## xmm0 = xmm0[0],xmm3[0],xmm0[2,3]
vinsertps $32, %xmm2, %xmm0, %xmm0 ## xmm0 = xmm0[0,1],xmm2[0],xmm0[3]
vinsertps $48, %xmm1, %xmm0, %xmm0 ## xmm0 = xmm0[0,1,2],xmm1[0]
vmovups %xmm0, (%rdi)
vzeroupper
retq</pre>
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</p>
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