[mlir][ods] Default-valued/optional parameters have default arguments

[Mogball]

Summary

Gives attribute and type C++ getters default-valued arguments for
optional ({}) and default-valued parameters.

Depends on D118544

[Mogball]

this on longer works because of the inclusion of $_ctx in the default value format

mlir/test/mlir-tblgen/attrdefs.td

def F_ParamWithAccessorTypeAttr : TestAttr<"ParamWithAccessorType"> {
   let parameters = (ins AttrParameter<"std::string", "", "StringRef">:$param);
 }
 
 // DECL-LABEL: class ParamWithAccessorTypeAttr
 // DECL: StringRef getParam()
 // DEF: ParamWithAccessorTypeAttrStorage
 // DEF: ParamWithAccessorTypeAttrStorage(std::string param)
 // DEF: StringRef ParamWithAccessorTypeAttr::getParam()
+
+
+def G_OptionalAndDefaultValuedParams
+    : TestAttr<"OptionalAndDefaultValuedParams"> {
+  let parameters = (ins OptionalParameter<"int *">:$a,
+                        DefaultValuedParameter<"int", "5">:$b);
+}
+
+// DECL-LABEL: class OptionalAndDefaultValuedParamsAttr
+// DECL: get(::mlir::MLIRContext *context, int *a = {}, int b = 5);

mlir/tools/mlir-tblgen/AttrOrTypeDefGen.cpp

 
 //===----------------------------------------------------------------------===//
 // Builder Emission
 
 SmallVector<MethodParameter>
 DefGen::getBuilderParams(std::initializer_list<MethodParameter> prefix) const {
   SmallVector<MethodParameter> builderParams;
   builderParams.append(prefix.begin(), prefix.end());
-  for (auto &param : params)
+  // Optional/default-valued parameters at the end of the parameter list can be
+  // given default arguments in C++.
+  auto paramsReverse = llvm::reverse(params);
+  auto lastOptional =
+      llvm::find_if(paramsReverse, [](const AttrOrTypeParameter &param) {
+        return !param.isOptional();
+      });
+  for (const AttrOrTypeParameter &param :
+       llvm::reverse(llvm::make_range(lastOptional, paramsReverse.end())))
     builderParams.emplace_back(param.getCppType(), param.getName());
+  for (const AttrOrTypeParameter &param :
+       llvm::reverse(llvm::make_range(paramsReverse.begin(), lastOptional))) {
+    Optional<StringRef> defaultValue = param.getDefaultValue();
+    builderParams.emplace_back(param.getCppType(), param.getName(),
+                               defaultValue ? *defaultValue : "{}");
+  }
   return builderParams;
 }
 
 void DefGen::emitDefaultBuilder() {
   Method *m = defCls.addStaticMethod(
       def.getCppClassName(), "get",
       getBuilderParams({{"::mlir::MLIRContext *", "context"}}));
   MethodBody &body = m->body().indent();