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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 --- - [AVX512] Masked instruction selection gets confused by bitcasts"
href="https://llvm.org/bugs/show_bug.cgi?id=26762">26762</a>
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<th>Summary</th>
<td>[AVX512] Masked instruction selection gets confused by bitcasts
</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>
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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
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</tr>
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
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</tr></table>
<p>
<div>
<pre>Creating a VPMOVZX by zero extend and then masking it correctly creates a
masked instruction:
define <16 x i16> @zext_mask_16x8_to_16x16(<16 x i8> %a, <16 x i1> %mask) {
%ext = zext <16 x i8> %a to <16 x i16>
%ret = select <16 x i1> %mask, <16 x i16> %ext, <16 x i16> zeroinitializer
ret <16 x i16> %ret
}
vpsllw $7, %xmm1, %xmm1
vpmovb2m %xmm1, %k1
vpmovzxbw %xmm0, %ymm0 {%k1} {z}
retq
But creating a VPMOVZX by a bitcasted shuffle fails to merge the mask:
define <16 x i16> @zext_mask_16x8_to_16x16(<16 x i8> %a, <16 x i1> %mask) {
%x = shufflevector <16 x i8> %a, <16 x i8> zeroinitializer, <32 x i32> <i32
0, i32 16, i32 1, i32 16, i32 2, i32 16, i32 3, i32 16, i32 4, i32 16, i32 5,
i32 16, i32 6, i32 16, i32 7, i32 16, i32 8, i32 16, i32 9, i32 16, i32 10, i32
16, i32 11, i32 16, i32 12, i32 16, i32 13, i32 16, i32 14, i32 16, i32 15, i32
16>
%bc = bitcast <32 x i8> %x to <16 x i16>
%ret = select <16 x i1> %mask, <16 x i16> %bc, <16 x i16> zeroinitializer
ret <16 x i16> %ret
}
vpsllw $7, %xmm1, %xmm1
vpmovb2m %xmm1, %k1
vpmovzxbw %xmm0, %ymm0
vmovdqu16 %ymm0, %ymm0 {%k1} {z}
retq</pre>
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</p>
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