[MLIR][NFC] Add FuncOp::addArgument() and FuncOp::getArgumentTypes()

[rriddle]

mlir/include/mlir/IR/FunctionSupport.h

223

This API is deceptive, as it doesn't add an argument to the type of the function itself. I would prefer we just don't add it.

[jurahul]

mlir/include/mlir/IR/FunctionSupport.h

223

That is true, it does a transient update. I agree not to put it (we can also update the type, but the use cases I have seen add multiple arguments, so we will end up instantiating a lot of FunctionType's in the process which is not desirable).

[jurahul]

Remove FuncOp::getArgument()

mlir/include/mlir/IR/FunctionSupport.h

public:
   /// Note that the concrete class must define a method with the same name to
   /// hide this one if the concrete class does not use FunctionType for the
   /// function type under the hood.
   void setType(FunctionType newType);
 
   //===--------------------------------------------------------------------===//
   // Argument Handling
   //===--------------------------------------------------------------------===//
+  using BlockArgListType = Region::BlockArgListType;
 
   unsigned getNumArguments() {
     return static_cast<ConcreteType *>(this)->getNumFuncArguments();
   }
 
   unsigned getNumResults() {
     return static_cast<ConcreteType *>(this)->getNumFuncResults();
   }
 
   /// Gets argument.
   BlockArgument getArgument(unsigned idx) { return getBody().getArgument(idx); }
 
   /// Support argument iteration.
   using args_iterator = Region::args_iterator;
   args_iterator args_begin() { return getBody().args_begin(); }
   args_iterator args_end() { return getBody().args_end(); }
   Block::BlockArgListType getArguments() { return getBody().getArguments(); }
 
+  ValueTypeRange<BlockArgListType> getArgumentTypes() {
+    return getBody().getArgumentTypes();
+  }
+
   //===--------------------------------------------------------------------===//
   // Argument Attributes
   //===--------------------------------------------------------------------===//
 
   /// FunctionLike operations allow for attaching attributes to each of the
   /// respective function arguments. These argument attributes are stored as
   /// DictionaryAttrs in the main operation attribute dictionary. The name of
   /// these entries is `arg` followed by the index of the argument. These