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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] failed to select vblendv with casted vector ops"
href="https://bugs.llvm.org/show_bug.cgi?id=32866">32866</a>
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<th>Summary</th>
<td>[x86] failed to select vblendv with casted vector ops
</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>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>spatel+llvm@rotateright.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<pre>Forking this off from <a class="bz_bug_link
bz_status_NEW "
title="NEW - Poor AVX code generation on 8xi1 masks"
href="show_bug.cgi?id=14657">bug 14657</a>.
This test exists in test/CodeGen/X86/cast-vsel.ll:
define <8 x i16> @trunc(<8 x i16> %a, <8 x i16> %b, <8 x i32> %c, <8 x i32> %d)
{
%cmp = icmp eq <8 x i16> %a, %b
%sel = select <8 x i1> %cmp, <8 x i32> %c, <8 x i32> %d
%tr = trunc <8 x i32> %sel to <8 x i16>
ret <8 x i16> %tr
}
After <a href="https://reviews.llvm.org/rL301781">https://reviews.llvm.org/rL301781</a> , this is effectively:
define <8 x i16> @trunc_first(<8 x i16> %a, <8 x i16> %b, <8 x i32> %c, <8 x
i32> %d) {
%cmp = icmp eq <8 x i16> %a, %b
%ctr = trunc <8 x i32> %c to <8 x i16>
%dtr = trunc <8 x i32> %d to <8 x i16>
%sel = select <8 x i1> %cmp, <8 x i16> %ctr, <8 x i16> %dtr
ret <8 x i16> %sel
}
For both AVX1 and AVX2, we fail to use vblendv in either case (avx2 shown
here):
_trunc_first: ## @trunc_first
.cfi_startproc
## BB#0:
vpcmpeqw %xmm1, %xmm0, %xmm0
vmovdqa LCPI1_0(%rip), %ymm1 ## ymm1 =
[0,1,4,5,8,9,12,13,8,9,12,13,12,13,14,15,16,17,20,21,24,25,28,29,24,25,28,29,28,29,30,31]
vpshufb %ymm1, %ymm2, %ymm2
vpermq $232, %ymm2, %ymm2 ## ymm2 = ymm2[0,2,2,3]
vpshufb %ymm1, %ymm3, %ymm1
vpermq $232, %ymm1, %ymm1 ## ymm1 = ymm1[0,2,2,3]
vpandn %xmm1, %xmm0, %xmm1
vpand %xmm0, %xmm2, %xmm0
vpor %xmm1, %xmm0, %xmm0
vzeroupper</pre>
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