| Issue |
202431
|
| Summary |
[CIR] Constant folding of vectors is incorrect
|
| Labels |
ClangIR
|
| Assignees |
|
| Reporter |
andykaylor
|
Constant folding of vectors in CIR is incorrect in two ways. First, when the result type of the compare is not a vector of i1, the result should be either 0 or -1, whereas we are currently folding to 0 or 1. Second, the folding of integer values is assuming that the value is signed, so the result is incorrectly computed for unsigned values.
Reproducer:
```
!u8i = !cir.int<u, 8>
!s8i = !cir.int<s, 8>
module {
cir.func @fold_cmp_vector_op_test() -> !cir.vector<4 x !s8i> {
%vec_1 = cir.const #cir.const_vector<[#cir.int<255> : !u8i, #cir.int<0> : !u8i, #cir.int<1> : !u8i, #cir.int<254> : !u8i]> : !cir.vector<4 x !u8i>
%vec_2 = cir.const #cir.const_vector<[#cir.int<254> : !u8i, #cir.int<255> : !u8i, #cir.int<255> : !u8i, #cir.int<255> : !u8i]> : !cir.vector<4 x !u8i>
%new_vec = cir.vec.cmp(gt, %vec_1, %vec_2) : !cir.vector<4 x !u8i>, !cir.vector<4 x !s8i>
cir.return %new_vec : !cir.vector<4 x !s8i>
}
}
```
The compare should fold to `cir.const #cir.const_vector<[#cir.int<-1> : !s8i, #cir.int<0> : !8i, #cir.int<0> : !s8i, #cir.int<0> : !s8i]> : !cir.vector<4 x !s8i>`. Instead it folds to `cir.const #cir.const_vector<[#cir.int<1> : !s8i, #cir.int<1> : !8i, #cir.int<1> : !s8i, #cir.int<0> : !s8i]> : !cir.vector<4 x !s8i>`
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