[mlir] Allow adding extra class declarations to interfaces.

[rriddle]

Summary

This matches the similar feature on operation definitions.

[jpienaar]

mlir/include/mlir/IR/OpBase.td

1508

So these would be placed alongside methods ?

[rriddle]

mlir/include/mlir/IR/OpBase.td

1508

Yes. For the side effect interfaces I want to have several template methods available, which is something you can't do with "interface methods".

mlir/include/mlir/IR/OpBase.td

class OpInterface<string name> : OpInterfaceTrait<name> {
   // A human-readable description of what this interface does.
   string description = "";
 
   // The name given to the c++ interface class.
   string cppClassName = name;
 
   // The list of methods defined by this interface.
   list<InterfaceMethod> methods = [];
+
+  // An optional code block containing extra declarations to place in the
+  // interface declaration.
+  code extraClassDeclaration = "";
 }
 
 // Whether to declare the op interface methods in the op's header. This class
 // simply wraps an OpInterface but is used to indicate that the method
 // declarations should be generated.
 class DeclareOpInterfaceMethods<OpInterface interface> :
   OpInterface<interface.cppClassName> {
     let description = interface.description;

mlir/include/mlir/TableGen/OpInterfaces.h

public:
   StringRef getName() const;
 
   // Return the methods of this interface.
   ArrayRef<OpInterfaceMethod> getMethods() const;
 
   // Return the description of this method if it has one.
   llvm::Optional<StringRef> getDescription() const;
 
+  // Return the interfaces extra class declaration code.
+  llvm::Optional<StringRef> getExtraClassDeclaration() const;
+
   // Return the verify method body if it has one.
   llvm::Optional<StringRef> getVerify() const;
 
 private:
   // The TableGen definition of this interface.
   const llvm::Record *def;
 
   // The methods of this interface.
   SmallVector<OpInterfaceMethod, 8> methods;
 };
 
 } // end namespace tblgen
 } // end namespace mlir
 
 #endif // MLIR_TABLEGEN_OPINTERFACES_H_

mlir/lib/TableGen/OpInterfaces.cpp

 ArrayRef<OpInterfaceMethod> OpInterface::getMethods() const { return methods; }
 
 // Return the description of this method if it has one.
 llvm::Optional<StringRef> OpInterface::getDescription() const {
   auto value = def->getValueAsString("description");
   return value.empty() ? llvm::Optional<StringRef>() : value;
 }
 
+// Return the interfaces extra class declaration code.
+llvm::Optional<StringRef> OpInterface::getExtraClassDeclaration() const {
+  auto value = def->getValueAsString("extraClassDeclaration");
+  return value.empty() ? llvm::Optional<StringRef>() : value;
+}
+
 // Return the body for this method if it has one.
 llvm::Optional<StringRef> OpInterface::getVerify() const {
   auto value = def->getValueAsString("verify");
   return value.empty() ? llvm::Optional<StringRef>() : value;
 }

mlir/tools/mlir-tblgen/OpInterfacesGen.cpp

static void emitInterfaceDecl(OpInterface &interface, raw_ostream &os) {
   emitTraitDecl(interface, os, interfaceName, interfaceTraitsName);
 
   // Insert the method declarations.
   for (auto &method : interface.getMethods()) {
     os << "  " << method.getReturnType() << " ";
     emitMethodNameAndArgs(method, os, /*addOperationArg=*/false);
     os << ";\n";
   }
+
+  // Emit any extra declarations.
+  if (Optional<StringRef> extraDecls = interface.getExtraClassDeclaration())
+    os << *extraDecls << "\n";
+
   os << "};\n";
 }
 
 static bool emitInterfaceDecls(const RecordKeeper &recordKeeper,
                                raw_ostream &os) {
   llvm::emitSourceFileHeader("Operation Interface Declarations", os);
 
   for (const auto *def : getAllOpInterfaceDefinitions(recordKeeper)) {