[mlir] Fix RankedTensorType::walkImmediateSubElements method

[vinograd47]

Summary

Add 'enconding' attribute visitor.
Without it ASM printer doesn't use attribute aliases for 'enconding'.

[rriddle]

mlir/lib/IR/BuiltinTypes.cpp

518–519

Please avoid recalculating the same thing.

[rriddle]

LGTM. May be good to add a test for this, e.g. testing assembly format alias generation for the encoding field.

[vinograd47]

Fixed review remarks.

[vinograd47]

@rriddle I've fixed your remarks.

mlir/lib/IR/BuiltinTypes.cpp

if (failed(v.verifyEncoding(shape, elementType, emitError)))
       return failure();
   return checkTensorElementType(emitError, elementType);
 }
 
 void RankedTensorType::walkImmediateSubElements(
     function_ref<void(Attribute)> walkAttrsFn,
     function_ref<void(Type)> walkTypesFn) const {
   walkTypesFn(getElementType());
+  if (getEncoding())
+    walkAttrsFn(getEncoding());
 }
 
 //===----------------------------------------------------------------------===//
 // UnrankedTensorType
 //===----------------------------------------------------------------------===//
 
 LogicalResult
 UnrankedTensorType::verify(function_ref<InFlightDiagnostic()> emitError,