[NFC][InstSimplify] Add miscompiled testcase from D87188/D87197
Thanks to Dave Green for producing an actionable reproducer!
It is (obviously) a miscompile:
```
----------------------------------------
define i32 @select_abs_of_abs_eq_wrong(i32 %x, i32 %y) {
%0:
%abs = abs i32 %x, 0
%neg = sub i32 0, %abs
%cmp = icmp eq i32 %y, 0
%sel = select i1 %cmp, i32 %neg, i32 %abs
ret i32 %sel
}
=>
define i32 @select_abs_of_abs_eq_wrong(i32 %x, i32 %y) {
%0:
%abs = abs i32 %x, 0
ret i32 %abs
}
Transformation doesn't verify!
ERROR: Value mismatch
Example:
i32 %x = #xe0000000 (
3758096384, -
536870912)
i32 %y = #x00000000 (0)
Source:
i32 %abs = #x20000000 (
536870912)
i32 %neg = #xe0000000 (
3758096384, -
536870912)
i1 %cmp = #x1 (1)
i32 %sel = #xe0000000 (
3758096384, -
536870912)
Target:
i32 %abs = #x20000000 (
536870912)
Source value: #xe0000000 (
3758096384, -
536870912)
Target value: #x20000000 (
536870912)
Alive2: Transform doesn't verify!
```