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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DAGCombiner] crash when forming shuffle from build vector"
href="https://bugs.llvm.org/show_bug.cgi?id=40394">40394</a>
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<th>Summary</th>
<td>[DAGCombiner] crash when forming shuffle from build vector
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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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>spatel+llvm@rotateright.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>This will crash using llc built from trunk r351752:
target triple = "aarch64-unknown-linux-gnu"
define <4 x i32> @truncating_build_vector_crash(<4 x i16> %t0) {
%t1 = extractelement <4 x i16> %t0, i32 2
%vgetq_lane = zext i16 %t1 to i32
%t2 = insertelement <4 x i32> undef, i32 %vgetq_lane, i64 0
ret <4 x i32> %t2
}
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The bug was introduced with:
<a href="https://reviews.llvm.org/D56281">https://reviews.llvm.org/D56281</a> / <a href="https://reviews.llvm.org/rL351198">https://reviews.llvm.org/rL351198</a>
I committed a fix that limits the transform to avoid the crash here:
<a href="https://reviews.llvm.org/rL351753">https://reviews.llvm.org/rL351753</a>
I think we should pull that commit into the 8.0 release to avoid the crash.</pre>
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