[MLIR] [LLVM Dialect] We lack PtrMask operation

[ChuanqiXu9]

If I didn't get things wrong, it looks like we don't have an op to model LLVM's ptrmask intrinsic (https://llvm.org/docs/LangRef.html#llvm-ptrmask-intrinsic). I can't find it in LLVMOps.td and LLVMIntrinsicOps.td.

[llvmbot]

@llvm/issue-subscribers-mlir-llvm

Author: Chuanqi Xu (ChuanqiXu9)

If I didn't get things wrong, it looks like we don't have an op to model LLVM's ptrmask intrinsic (https://llvm.org/docs/LangRef.html#llvm-ptrmask-intrinsic). I can't find it in LLVMOps.td and LLVMIntrinsicOps.td.