[llvm-bugs] [Bug 49832] New: InstCombine incorrectly folds select of vector

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49832

            Bug ID: 49832
           Summary: InstCombine incorrectly folds select of vector
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: juneyoung.lee at sf.snu.ac.kr
                CC: llvm-bugs at lists.llvm.org

```
$ 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: https://alive2.llvm.org/ce/z/8X-4kR
If input is <0, 2>, (%x, %y) is (2, 2) in src, but it becomes (0, 2) in tgt.

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