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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Lower shuffles using AVX-512 EXPAND* instructions"
href="https://llvm.org/bugs/show_bug.cgi?id=31351">31351</a>
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<th>Summary</th>
<td>Lower shuffles using AVX-512 EXPAND* instructions
</td>
</tr>
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<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>normal
</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>zvi.rackover@intel.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>define <8 x float> @expand(<4 x float> %a) {
%res = shufflevector <4 x float> %a, <4 x float> zeroinitializer, <8 x i32>
<i32 0, i32 5, i32 1, i32 5, i32 2, i32 5, i32 3, i32 5>
ret <8 x float> %res
}
We currently generate:
vmovaps .LCPI0_0(%rip), %ymm1 # ymm1 = <0,u,1,u,2,u,3,u>
vpermps %ymm0, %ymm1, %ymm0
vxorps %ymm1, %ymm1, %ymm1
vblendps $170, %ymm1, %ymm0, %ymm0 # ymm0 =
ymm0[0],ymm1[1],ymm0[2],ymm1[3],ymm0[4],ymm1[5],ymm0[6],ymm1[7]
This would be better:
mov $mask, %eax
mov $eax, %k1
expandps %ymm0, %ymm0 {%k1}{z}:</pre>
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