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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - shuffling instead of moving high element directly (x86)"
href="http://llvm.org/bugs/show_bug.cgi?id=21791">21791</a>
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<th>Summary</th>
<td>shuffling instead of moving high element directly (x86)
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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
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>spatel+llvm@rotateright.com
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</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
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<p>
<div>
<pre>In this test case, we want to store the high element of the vector:
$ cat get_high.ll
define void @get_high(<2 x double> %v, double* %ptr) {
%vecext1 = extractelement <2 x double> %v, i32 1
store double %vecext1, double* %ptr, align 8
ret void
}
With plain SSE2:
$ ./llc get_high.ll -o -
...
shufpd $1, %xmm0, %xmm0 ## xmm0 = xmm0[1,0]
movlpd %xmm0, (%rdi)
retq
With AVX:
$ ./llc -mcpu=btver2 get_high.ll -o -
...
vpermilpd $1, %xmm0, %xmm0 ## xmm0 = xmm0[1,0]
vmovlpd %xmm0, (%rdi)
retq
---------------------------------------------------------------------
I think we should be generating '(v)movhpd' instead; no shuffles needed.</pre>
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</p>
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