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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - InstCombine incorrectly folds select of vector"
href="https://bugs.llvm.org/show_bug.cgi?id=49832">49832</a>
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<th>Summary</th>
<td>InstCombine incorrectly folds select of vector
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
<tr>
<th>Reporter</th>
<td>juneyoung.lee@sf.snu.ac.kr
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>```
$ cat src.ll
define void @src(<2 x i32> %input) {
%cond = icmp eq <2 x i32> %input, zeroinitializer
%.14 = extractelement <2 x i32> %input, i32 1
%.15 = insertelement <2 x i32> poison, i32 %.14, i32 0
%.16 = extractelement <2 x i32> %input, i32 0
%.17 = insertelement <2 x i32> %.15, i32 %.16, i32 1
%.18 = select <2 x i1> %cond, <2 x i32> %.17, <2 x i32> %input
%x = extractelement <2 x i32> %.18, i32 0
%y = extractelement <2 x i32> %.18, i32 1
call void @f(i32 %x, i32 %y)
ret void
}
declare void @f(i32, i32)
$ opt -instcombine -S -o - src.ll
define void @src(<2 x i32> %input) {
%x = extractelement <2 x i32> %input, i32 0
%y = extractelement <2 x i32> %input, i32 1
call void @f(i32 %x, i32 %y)
ret void
}
declare void @f(i32, i32)
```
This is incorrect: <a href="https://alive2.llvm.org/ce/z/8X-4kR">https://alive2.llvm.org/ce/z/8X-4kR</a>
If input is <0, 2>, (%x, %y) is (2, 2) in src, but it becomes (0, 2) in tgt.</pre>
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