[DialectAsmPrinter] Add missing 'printAttributeWithoutType' member.

[lattner]

Summary

DialectAsmParser has a parseAttribute member that takes a
contextual type, but DialectAsmPrinter doesn't have the corresponding
member to take advantage of it. As such, custom attribute
implementations can't really use it. This adds the obvious missing
method which fills this hole.

[lattner]

I plan to land this as "obvious" after the smoke tests pass. Incidentally, there is a ton of duplication between DialectImplementation.h and OpImplemention.h, I wonder if there is a way to factor this better?

[mehdi_amini]

Any chance we can get a test op to use this?

[lattner]

Fix this to build.

[lattner]

Any chance we can get a test op to use this?

Oh sorry, didn't see this. Yes, I can add a test for this if needed, is circt using this enough? This isn't likely to break or regress.

If that's not enough, I'll have to add a custom attribute, because ops don't use this printer path (that's the root problem :)

mlir/include/mlir/IR/DialectImplementation.h

 public:
   DialectAsmPrinter() {}
   virtual ~DialectAsmPrinter();
   virtual raw_ostream &getStream() const = 0;
 
   /// Print the given attribute to the stream.
   virtual void printAttribute(Attribute attr) = 0;
 
+  /// Print the given attribute without its type. The corresponding parser must
+  /// provide a valid type for the attribute.
+  virtual void printAttributeWithoutType(Attribute attr) = 0;
+
   /// Print the given floating point value in a stabilized form that can be
   /// roundtripped through the IR. This is the companion to the 'parseFloat'
   /// hook on the DialectAsmParser.
   virtual void printFloat(const APFloat &value) = 0;
 
   /// Print the given type to the stream.
   virtual void printType(Type type) = 0;
 

mlir/lib/IR/AsmPrinter.cpp

public:
   CustomDialectAsmPrinter(ModulePrinter &printer) : printer(printer) {}
   ~CustomDialectAsmPrinter() override {}
 
   raw_ostream &getStream() const override { return printer.getStream(); }
 
   /// Print the given attribute to the stream.
   void printAttribute(Attribute attr) override { printer.printAttribute(attr); }
 
+  /// Print the given attribute without its type. The corresponding parser must
+  /// provide a valid type for the attribute.
+  void printAttributeWithoutType(Attribute attr) override {
+    printer.printAttribute(attr, ModulePrinter::AttrTypeElision::Must);
+  }
+
   /// Print the given floating point value in a stablized form.
   void printFloat(const APFloat &value) override {
     printFloatValue(value, getStream());
   }
 
   /// Print the given type to the stream.
   void printType(Type type) override { printer.printType(type); }