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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [InstCombine] Support non-uniform constant vectors for mul -> shl"
href="https://bugs.llvm.org/show_bug.cgi?id=35874">35874</a>
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<th>Summary</th>
<td>[InstCombine] Support non-uniform constant vectors for mul -> shl
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Common Code Generator Code
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
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<th>CC</th>
<td>david.majnemer@gmail.com, efriedma@codeaurora.org, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
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</tr></table>
<p>
<div>
<pre>rL322072 demonstrates several cases where only scalars/uniform-vectors are
actually combined:
e.g.
define <2 x i17> @test2(<2 x i17> %X) {
; CHECK-LABEL: @test2(
; CHECK-NEXT: [[Y:%.*]] = shl <2 x i17> [[X:%.*]], <i17 10, i17 10>
; CHECK-NEXT: ret <2 x i17> [[Y]]
;
%Y = mul <2 x i17> %X, <i17 1024, i17 1024>
ret <2 x i17> %Y
}
define <2 x i17> @test3(<2 x i17> %X) {
; CHECK-LABEL: @test3(
; CHECK-NEXT: [[Y:%.*]] = mul <2 x i17> [[X:%.*]], <i17 1024, i17 256>
; CHECK-NEXT: ret <2 x i17> [[Y]]
;
%Y = mul <2 x i17> %X, <i17 1024, i17 256>
ret <2 x i17> %Y
}
It'd be very useful to support non-uniform vectors, possibly through a similar
approach to DAGCombine's matchUnaryPredicate/matchBinaryPredicate mechanism.
This is the tip of iceberg as most InstCombine patterns don't support
non-uniform vectors.</pre>
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