[mlir][linalg] Add a FillOpInterface.

Add a FillOpInterface similar to the contraction and convolution op interfaces. The FillOpInterface is a preparation step to replace linalg.fill by its OpDSL version linalg.fill_tensor. The interface implements the `value()`, `output()`, and `result()` methods that by default are not available on linalg.fill_tensor.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D120725

mlir/python/mlir/dialects/linalg/opdsl/lang/comprehension.py

@@ -686,6 +686,7 @@ class OpInterfaceDef:
 
 ContractionOpInterface = OpInterfaceDef("LinalgContractionOpInterface")
 ConvolutionOpInterface = OpInterfaceDef("LinalgConvolutionOpInterface")
+FillOpInterface = OpInterfaceDef("LinalgFillOpInterface")
 
 
 class OpMetadataDef(YAMLObject):

mlir/python/mlir/dialects/linalg/opdsl/ops/core_named_ops.py

@@ -671,6 +671,7 @@ def fill_tensor(value=ScalarDef(T1), O=TensorDef(U, output=True)):
   accesses only and is thus rank polymorphic. Numeric casting is performed on
   the value operand, promoting it to the same data type as the output.
   """
+  implements(FillOpInterface)
   O[None] = TypeFn.cast_signed(U, value)