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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [X86] Use combineLogicBlendIntoConditionalNegate for SSSE3+ targets"
href="https://bugs.llvm.org/show_bug.cgi?id=43660">43660</a>
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<th>Summary</th>
<td>[X86] Use combineLogicBlendIntoConditionalNegate for SSSE3+ targets
</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>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>Current Codegen: <a href="https://gcc.godbolt.org/z/mmT1B1">https://gcc.godbolt.org/z/mmT1B1</a>
As mentioned on D62777, basic SSE2 targets manage to simplify:
define <16 x i8> @non_splat_minus_one_divisor_0(<16 x i8> %A) {
%div = sdiv <16 x i8> %A, <i8 -1, i8 -1, i8 1, i8 -1, i8 -1, i8 -1, i8 1, i8
-1, i8 -1, i8 1, i8 1, i8 1, i8 1, i8 1, i8 1, i8 1>
ret <16 x i8> %div
}
to:
non_splat_minus_one_divisor_0: # @non_splat_minus_one_divisor_0
movdqa .LCPI0_0(%rip), %xmm1 # xmm1 =
[0,0,255,0,0,0,255,0,0,255,255,255,255,255,255,255]
pxor %xmm1, %xmm0
psubb %xmm0, %xmm1
movdqa %xmm1, %xmm0
retq
but later targets end up with:
non_splat_minus_one_divisor_0: # @non_splat_minus_one_divisor_0
pxor %xmm1, %xmm1
psubb %xmm0, %xmm1
pshufb .LCPI0_0(%rip), %xmm1 # xmm1 =
xmm1[0,1],zero,xmm1[3,4,5],zero,xmm1[7,8],zero,zero,zero,zero,zero,zero,zero
pshufb .LCPI0_1(%rip), %xmm0 # xmm0 =
zero,zero,xmm0[2],zero,zero,zero,xmm0[6],zero,zero,xmm0[9,10,11,12,13,14,15]
por %xmm1, %xmm0
retq
or (after SSE41):
non_splat_minus_one_divisor_0: # @non_splat_minus_one_divisor_0
vmovdqa .LCPI0_0(%rip), %xmm2 # xmm2 =
[0,0,255,0,0,0,255,0,0,255,255,255,255,255,255,255]
vpxor %xmm1, %xmm1, %xmm1
vpsubb %xmm0, %xmm1, %xmm1
vpblendvb %xmm2, %xmm0, %xmm1, %xmm0
retq</pre>
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