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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [X86][AVX] Failure to generate vaddsubps for pattern after 19b62b79"
href="https://bugs.llvm.org/show_bug.cgi?id=45015">45015</a>
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<th>Summary</th>
<td>[X86][AVX] Failure to generate vaddsubps for pattern after 19b62b79
</td>
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<th>Product</th>
<td>new-bugs
</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>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>douglas_yung@playstation.sony.com
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</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<pre>Consider the following code:
#include <x86intrin.h>
__m128 haddsub0ps(__m128 a, __m128 b) {
return (__m128){ a[0] - b[0], a[1] + b[1], a[2] - b[2], a[3] + b[3] };
}
Prior to commit 19b62b79db1bb154b40e8baba9a28ab8aa935b6b, when compiled with
optimizations and avx (-O2 -mavx), the compiler would generate the following
assembly:
vaddsubps %xmm1, %xmm0, %xmm0
But now the compiler is instead generating the following assembly:
vsubss %xmm1, %xmm0, %xmm2
vaddps %xmm1, %xmm0, %xmm3
vblendps $1, %xmm2, %xmm3, %xmm2 # xmm2 = xmm2[0],xmm3[1,2,3]
vsubps %xmm1, %xmm0, %xmm0
vblendps $3, %xmm2, %xmm0, %xmm0 # xmm0 = xmm2[0,1],xmm0[2,3]
vblendps $8, %xmm3, %xmm0, %xmm0 # xmm0 = xmm0[0,1,2],xmm3[3]</pre>
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