b003c60904
There are multiple ways to define a remainder operation. Depending on the definition, the result could be either always positive or have the sign of the dividend. The pattern lowering `arith.remf` to LLVM assumes that the semantics match `llvm.frem`, which seems to be reasonable. The folder, however, is implemented via `APFloat::remainder()` which has different semantics. This patch matches the folding behaviour to lowering behavior by using `APFloat::mod()`, which matches the behavior of `llvm.frem` and libm's `fmod()`. It also updates the documentation of `arith.remf` to explain this behavior: The sign of the result of the remainder operation always matches the sign of the dividend (LHS operand). frem documentation: https://llvm.org/docs/LangRef.html#frem-instruction Fix https://github.com/llvm/llvm-project/issues/94431 --------- Co-authored-by: Jakub Kuderski <kubakuderski@gmail.com>