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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [X86] reduceBuildVecExtToExtBuildVec breaks uses of opportunity to use broadcast"
href="https://bugs.llvm.org/show_bug.cgi?id=46461">46461</a>
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<th>Summary</th>
<td>[X86] reduceBuildVecExtToExtBuildVec breaks uses of opportunity to use broadcast
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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
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>craig.topper@gmail.com
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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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<pre>This code compiled with avx2 produces multiple vpinsrw instead of just
broadcasting the i32 scalar
define <16 x i32> @bar(i16 %x) {
%a = zext i16 %x to i32
%b = insertelement <16 x i32> undef, i32 %a, i32 0
%c = shufflevector <16 x i32> %b, <16 x i32> undef, <16 x i32>
zeroinitializer
ret <16 x i32> %c
}
<a href="https://godbolt.org/z/K23-jp">https://godbolt.org/z/K23-jp</a>
Should we disable reduceBuildVecExtToExtBuildVec for splat vectors or should we
improve our broadcast matching? I kind of think that even without native
broadcast we could still use pshufd to broadcast instead of multiple inserts.</pre>
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