eae5ca9b45
This PR extends the existing poison support in https://mlir.llvm.org/docs/Dialects/UBOps/ by representing poison mask values in `vector.shuffle`. Similar to LLVM (see https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/IR/Instructions.h#L1884) this requires defining an integer value (`-1`) to represent poison in the `vector.shuffle` mask.