[mlir] Remove unnecessary llvm.mlir.cast in AsyncToLLVM lowering.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D94400

Author: chsigg

mlir/lib/Conversion/AsyncToLLVM/AsyncToLLVM.cpp

@@ -945,13 +945,7 @@ class AwaitValueOpLowering : public AwaitOpLoweringBase<AwaitOp, ValueType> {
         loc, LLVM::LLVMPointerType::get(llvmValueType), storage.getResult(0));
 
     // Load from the async value storage.
-    auto loaded = rewriter.create<LLVM::LoadOp>(loc, castedStorage.getResult());
-
-    // Cast from LLVM type to the expected value type if necessary. This cast
-    // will become no-op after lowering to LLVM.
-    if (valueType == loaded.getType())
-      return loaded;
-    return rewriter.create<LLVM::DialectCastOp>(loc, valueType, loaded);
+    return rewriter.create<LLVM::LoadOp>(loc, castedStorage.getResult());
   }
 };