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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 - [VectorCombine] Generated code no longer uses horizontal add/sub"
href="https://bugs.llvm.org/show_bug.cgi?id=45747">45747</a>
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<th>Summary</th>
<td>[VectorCombine] Generated code no longer uses horizontal add/sub
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>Wolfgang_Pieb@playstation.sony.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<pre>After
<a href="https://github.com/llvm/llvm-project/commit/a69158c12acd635ee4bcb22b1060d92b29483042">https://github.com/llvm/llvm-project/commit/a69158c12acd635ee4bcb22b1060d92b29483042</a>
the following test cases no longer generate horizontal add/sub for the
following test cases:
==========================================================================
typedef float __m128 __attribute__((__vector_size__(16), __aligned__(16)));
__m128 add_ps_002(__m128 a, __m128 b) {
__m128 r = (__m128){ a[0] + a[1], a[2] + a[3], b[0] + b[1], b[2] + b[3] };
return __builtin_shufflevector(r, a, -1, 1, -1, -1);
}
__m128 add_ps_013(__m128 a, __m128 b) {
__m128 r = (__m128){ a[0] + a[1], a[2] + a[3], b[0] + b[1], b[2] + b[3] };
return __builtin_shufflevector(r, a, 3, -1, -1, -1);
}
==========================================================================
The diffs (old code first):
< vhaddps %xmm0, %xmm0, %xmm0
< vmovshdup %xmm0, %xmm0 # xmm0 = xmm0[1,1,3,3]
---
<span class="quote">> vmovshdup %xmm0, %xmm1 # xmm1 = xmm0[1,1,3,3]
> vaddps %xmm0, %xmm1, %xmm0
> vpermilps $232, %xmm0, %xmm0 # xmm0 = xmm0[0,2,2,3]</span >
24,25c25,27
< vhaddps %xmm1, %xmm1, %xmm0
< vmovshdup %xmm0, %xmm0 # xmm0 = xmm0[1,1,3,3]
---
<span class="quote">> vmovshdup %xmm1, %xmm0 # xmm0 = xmm1[1,1,3,3]
> vaddps %xmm1, %xmm0, %xmm0
> vpermilpd $1, %xmm0, %xmm0 # xmm0 = xmm0[1,0]</span ></pre>
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