[mlir][Linalg] Slightly adjust DestinationStyleOpInterface.

[akuegel]

Summary

Rename some interface methods to be consistent with the new accessor names.
This is a preparation for adding a ReduceOp, which then will implement
getIteratorTypes() and getOutputs() instead of iterator_types() and outputs().

[akuegel]

@nicolasvasilache I have extracted this change from https://reviews.llvm.org/D134731 as it is a potentially breaking change for downstream users.
Seems safer to have that in a separate patch.
More cleanup for this interface needs to be done in the future, but @pifon2a is already working on it, so I would prefer to keep this change limited to what we need for ReduceOp.

[pifon2a]

Thank you, Adrian!

[nicolasvasilache]

In D134868#3823335, @akuegel wrote:

@nicolasvasilache I have extracted this change from https://reviews.llvm.org/D134731 as it is a potentially breaking change for downstream users.
Seems safer to have that in a separate patch.
More cleanup for this interface needs to be done in the future, but @pifon2a is already working on it, so I would prefer to keep this change limited to what we need for ReduceOp.

Sounds great to me, thanks for improving this for all of us!

mlir/include/mlir/Dialect/Linalg/IR/LinalgInterfaces.td

InterfaceMethod<
       /*desc=*/[{
         Return the iterator types attribute within the current operation.
       }],
       /*retTy=*/"ArrayAttr",
       /*methodName=*/"iterator_types",
       /*args=*/(ins),
       /*methodBody=*/"",
       /*defaultImplementation=*/[{
-        return $_op.iterator_types();
+        return $_op.getIteratorTypes();
       }]
     >,
     InterfaceMethod<
       /*desc=*/[{
         Return iterator types in the current operation.
       }],
       /*retTy=*/"SmallVector<StringRef>",
       /*methodName=*/"getIteratorTypesArray",
let extraClassDeclaration = [{
     }
 
     int64_t getNumInputs() {
       return cast<DestinationStyleOpInterface>(*this->getOperation())
           .getNumInputs();
     }
 
     ValueRange outputs() {
-      return cast<DestinationStyleOpInterface>(*this->getOperation()).outputs();
+      return cast<DestinationStyleOpInterface>(*this->getOperation())
+          .getOutputs();
     }
 
     int64_t getNumOutputs() {
       return cast<DestinationStyleOpInterface>(*this->getOperation())
           .getNumOutputs();
     }
 
     int64_t getNumInputsAndOutputs() {
def LinalgStructuredInterface : OpInterface<"LinalgOp"> {
 
   let verify = [{ return detail::verifyStructuredOpInterface($_op); }];
   let verifyWithRegions = 1;
 }
 
 // The 'DestinationStyleOpInterface' provides access to the methods relevant
 // for destination-style ops. A destination-style operation has 'n' input
 // arguments and 'm' output arguments. Each op that wants to implement
-// DestinationStyleOpInterface needs to define inputs() and outputs() methods.
+// DestinationStyleOpInterface needs to define inputs() and getOutputs()
+// methods.
 def DestinationStyleOpInterface : OpInterface<"DestinationStyleOpInterface"> {
   let cppNamespace = "::mlir::linalg";
   let methods = [
     //===------------------------------------------------------------------===//
     // Num input/output arguments handling.
     //===------------------------------------------------------------------===//
     // `inputs` must be defined by each op that wants to implement the
     // DestinationStyleOpInterface.
InterfaceMethod<
       /*retTy=*/"int64_t",
       /*methodName=*/"getNumInputs",
       /*args=*/(ins),
       /*methodBody=*/"",
       /*defaultImplementation=*/[{
         return $_op.getInputs().size();
       }]
     >,
-    // `outputs` must be defined by each op that wants to implement the
+    // `getOutputs` must be defined by each op that wants to implement the
     // DestinationStyleOpInterface.
     InterfaceMethod<
       /*desc=*/[{
         Return the output shape operands.
       }],
       /*retTy=*/"ValueRange",
-      /*methodName=*/"outputs",
+      /*methodName=*/"getOutputs",
       /*args=*/(ins)
     >,
     InterfaceMethod<
       /*desc=*/[{
         Return the number of outputs.
       }],
       /*retTy=*/"int64_t",
       /*methodName=*/"getNumOutputs",
       /*args=*/(ins),
       /*methodBody=*/"",
       /*defaultImplementation=*/[{
-        return $_op.outputs().size();
+        return $_op.getOutputs().size();
       }]
     >,
     InterfaceMethod<
       /*desc=*/[{
         Return the number of inputs and outputs.
       }],
       /*retTy=*/"int64_t",
       /*methodName=*/"getNumInputsAndOutputs",