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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [X86] Avoid scalar/vector transfers for scalar arithmetic"
href="https://bugs.llvm.org/show_bug.cgi?id=42633">42633</a>
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<th>Summary</th>
<td>[X86] Avoid scalar/vector transfers for scalar arithmetic
</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>Windows NT
</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>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
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<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
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<p>
<div>
<pre><a href="https://godbolt.org/z/LvQiCP">https://godbolt.org/z/LvQiCP</a>
#include <x86intrin.h>
auto add(__v4si x) {
return _mm_set1_epi32(x[1] + x[3]);
}
_Z3addDv4_i:
vextractps $1, %xmm0, %eax
vextractps $3, %xmm0, %ecx
addl %eax, %ecx
vmovd %ecx, %xmm0
vpshufd $0, %xmm0, %xmm0 # xmm0 = xmm0[0,0,0,0]
retq
A more optimal method would be something like:
add(int __vector(4)):
vpshufd xmm1, xmm0, 78 # xmm1 = xmm0[2,3,0,1]
vpaddd xmm0, xmm1, xmm0
vpshufd xmm0, xmm0, 85 # xmm0 = xmm0[1,1,1,1]
ret</pre>
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