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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] Reductions should use smaller vector types later on"
href="https://bugs.llvm.org/show_bug.cgi?id=38971">38971</a>
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<th>Summary</th>
<td>[X86] Reductions should use smaller vector types later on
</td>
</tr>
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<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>Windows NT
</td>
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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>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
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<th>CC</th>
<td>andrea.dibiagio@gmail.com, craig.topper@gmail.com, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
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<p>
<div>
<pre><a href="https://godbolt.org/z/v--jOA">https://godbolt.org/z/v--jOA</a>
define float @test_v8f32(float %a0, <8 x float> %a1) {
%1 = call fast float
@llvm.experimental.vector.reduce.fadd.f32.f32.v8f32(float %a0, <8 x float> %a1)
ret float %1
}
declare float @llvm.experimental.vector.reduce.fadd.f32.f32.v8f32(float, <8 x
float>)
llc -mcpu=btver2
test_v8f32:
vextractf128 $1, %ymm1, %xmm0
vaddps %ymm0, %ymm1, %ymm0
vpermilpd $1, %xmm0, %xmm1 # xmm1 = xmm0[1,0]
vaddps %ymm1, %ymm0, %ymm0
vhaddps %ymm0, %ymm0, %ymm0
retq
All of the vaddps/vhaddps stages could occur using xmm registers, which would
have a notable performance effect on btver2 which double pumps ymm ops as
2*128-bit.</pre>
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