[llvm-bugs] [Bug 47668] New: foldSelectICmpAndAnd should check whether the shift amount is less than bitwidth

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=47668

            Bug ID: 47668
           Summary: foldSelectICmpAndAnd should check whether the shift
                    amount is less than bitwidth
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: MacOS X
            Status: NEW
          Severity: normal
          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

File: test/Transforms/InstCombine/select-of-bittest.ll 
```
define i32 @f_var2(i32 %arg, i32 %arg1) {
%0:
  %tmp = and i32 %arg, 1
  %tmp2 = icmp eq i32 %tmp, 0
  %tmp3 = lshr i32 %arg, %arg1
  %tmp4 = and i32 %tmp3, 1
  %tmp5 = select i1 %tmp2, i32 %tmp4, i32 1
  ret i32 %tmp5
}
=>
define i32 @f_var2(i32 %arg, i32 %arg1) {
%0:
  %1 = shl i32 1, %arg1
  %2 = or i32 %1, 1
  %3 = and i32 %2, %arg
  %4 = icmp ne i32 %3, 0
  %tmp5 = zext i1 %4 to i32
  ret i32 %tmp5
}
Transformation doesn't verify!
ERROR: Target is more poisonous than source

Example:
i32 %arg = #x00000001 (1)
i32 %arg1 = poison

Source:
i32 %tmp = #x00000001 (1)
i1 %tmp2 = #x0 (0)
i32 %tmp3 = poison
i32 %tmp4 = poison
i32 %tmp5 = #x00000001 (1)

Target:
i32 %1 = poison
i32 %2 = poison
i32 %3 = poison
i1 %4 = poison
i32 %tmp5 = poison
Source value: #x00000001 (1)
Target value: poison
```

Relevant revision: https://reviews.llvm.org/D45108
The revision includes Alive proof, but its precondition wasn't encoded.
I'll make a patch for this.

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