| Issue |
76441
|
| Summary |
Incorrect instcombine optimization
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
ericastor
|
Demonstration in alive2: https://alive2.llvm.org/ce/z/B5daAG
The function
```
define i128 @f(i128 %x) {
entry:
%0 = and i128 %x, 36893488147419103231
%1 = xor i128 %0, -1
%2 = and i128 %1, 36893488147419103231
%3 = xor i128 %x, -1
%4 = and i128 %3, 36893488147419103231
%5 = add i128 %2, %4
%6 = and i128 %5, 36893488147419103231
ret i128 %6
}
```
incorrectly optimizes to:
```
define i128 @f(i128 %x) {
entry:
%0 = shl i128 %x, 1
%1 = sub i128 18446744073709551614, %0
%2 = and i128 %1, 36893488147419103230
ret i128 %2
}
```
which disagrees on input 0.
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