[triton-mlir][BACKEND] Support masked load/store (#657)

This PR does

- fix some bugs to support masked load/store,
- refine frontend, and support the `and` and `or` syntax in mask(by
extending the BoolOp in python ast.visitor), e.g. `tl.store(...,
mask=offset<n and other_conditions)`,
- add `arith.cmpI` and `arith.cmpF` op conversion in backend(required by
mask),
- add more test cases in vecadd.

python/src/triton.cc

@@ -1210,6 +1210,8 @@ void init_triton_translation(py::module &m) {
         llvm::LLVMContext llvmContext;
         auto llvmModule =
             ::mlir::triton::translateTritonGPUToLLVMIR(&llvmContext, op);
+        if (!llvmModule)
+          llvm::report_fatal_error("Failed to translate TritonGPU to LLVM IR.");
 
         std::string str;
         llvm::raw_string_ostream os(str);