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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DAGCombine] Scalarizing vector ops with low/one demanded elements"
href="https://bugs.llvm.org/show_bug.cgi?id=39973">39973</a>
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<th>Summary</th>
<td>[DAGCombine] Scalarizing vector ops with low/one demanded elements
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Common Code Generator Code
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
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<th>CC</th>
<td>andrea.dibiagio@gmail.com, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
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<p>
<div>
<pre>As mentioned in <a href="https://reviews.llvm.org/D55558">https://reviews.llvm.org/D55558</a>
<a href="https://godbolt.org/z/-1CEbS">https://godbolt.org/z/-1CEbS</a>
define i32 @knownbits_mask_extract_sext(<8 x i16> %a0) nounwind {
%1 = and <8 x i16> %a0, <i16 15, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16
-1, i16 -1>
%2 = extractelement <8 x i16> %1, i32 0
%3 = sext i16 %2 to i32
ret i32 %3
}
As this uses only a single element, should it be scalarized?
knownbits_mask_extract_sext: # @knownbits_mask_extract_sext
vpand .LCPI0_0(%rip), %xmm0, %xmm0
vpextrw $0, %xmm0, %eax
retq
knownbits_mask_extract_sext_alt: # @knownbits_mask_extract_sext_alt
vmovd %xmm0, %eax
andl $15, %eax
retq</pre>
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