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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [AArch64] Build improper vector filled with undef when constant folding vselect."
href="http://llvm.org/bugs/show_bug.cgi?id=20396">20396</a>
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<th>Summary</th>
<td>[AArch64] Build improper vector filled with undef when constant folding vselect.
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</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>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>new bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>kevinqindev@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Testcase:
$cat test.ll
define <8 x i16> @test() {
entry:
%mul.i = select <8 x i1> <i1 true, i1 false, i1 false, i1 true, i1 true, i1
false, i1 false, i1 true>, <8 x i16> <i16 0, i16 undef, i16 undef, i16 0, i16
0, i16 undef, i16 undef, i16 0>, <8 x i16> zeroinitializer
%add.i = add <8 x i16> %mul.i, <i16 1, i16 1, i16 1, i16 1, i16 1, i16 1, i16
1, i16 1>
ret <8 x i16> %add.i
}
Output:
$llc -mtriple=aarch64 <test.ll
LLVM ERROR: Cannot select: 0x4d423f8: v8i16 = BUILD_VECTOR 0x4d44de8,
0x4d44ce0, 0x4d44ce0, 0x4d44de8, 0x4d44de8, 0x4d44ce0, 0x4d44ce0, 0x4d44de8
[ORD=2] [ID=10]
0x4d44de8: i32 = Constant<0> [ID=4]
0x4d44ce0: i32 = undef [ID=3]
0x4d44ce0: i32 = undef [ID=3]
0x4d44de8: i32 = Constant<0> [ID=4]
0x4d44de8: i32 = Constant<0> [ID=4]
0x4d44ce0: i32 = undef [ID=3]
0x4d44ce0: i32 = undef [ID=3]
0x4d44de8: i32 = Constant<0> [ID=4]
It seems that it's caused by the bug in DAGcombiner when doing constant fold on
expanded vselect.</pre>
</div>
</p>
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