[flang][NFC] Wrap TBAABuilder in unique_ptr

[springerm]

Summary

The fir::LLVMTypeConverter has a TBAABuilder. The current design prevents the type converter stored in conversion patterns from being const. This is generally dangerous because type conversion rules should not change during a dialect conversion.

This revision wraps the TBAABuilder in a unique_ptr. That way, the type converter itself can be const, but the TBAABuilder can still have mutable state. (What's important form an MLIR perspective is that the type conversion rules cannot change.)

This change is needed for D157601.

[springerm]

flang/include/flang/Optimizer/CodeGen/TypeConverter.h

149

Alternatively, this could be turned into a TBAABuilder * const.

[vzakhari]

There is the following comment in TypeConverter.cpp:LLVMTypeConverter::convertBoxType:

// TODO: send the box type and the converted LLVM structure layout
// to tbaaBuilder for proper creation of TBAATypeDescriptorOp.

In future, we may need the original and the converted box type to create more precise TBAA type descriptor. I am not sure if it will be convenient to do outside of the type converter. If you insist on making this change, please, make sure you remove the TODO comment.

[springerm]

keep TBAABuilder in type converter

[springerm]

In D157611#4578812, @vzakhari wrote:

There is the following comment in TypeConverter.cpp:LLVMTypeConverter::convertBoxType:

// TODO: send the box type and the converted LLVM structure layout
// to tbaaBuilder for proper creation of TBAATypeDescriptorOp.

In future, we may need the original and the converted box type to create more precise TBAA type descriptor. I am not sure if it will be convenient to do outside of the type converter. If you insist on making this change, please, make sure you remove the TODO comment.

OK, then let's keep the TBAABuilder there for the moment. Wrapping it in a unique_ptr also works. I just want to make sure that the base type conversion state (i.e., conversion rules) is immutable.

[springerm]

merged into D157601

flang/include/flang/Optimizer/CodeGen/TypeConverter.h

public:
   // Relay TBAA tag attachment to TBAABuilder.
   void attachTBAATag(mlir::LLVM::AliasAnalysisOpInterface op,
                      mlir::Type baseFIRType, mlir::Type accessFIRType,
                      mlir::LLVM::GEPOp gep);
 
 private:
   KindMapping kindMapping;
   std::unique_ptr<CodeGenSpecifics> specifics;
-  TBAABuilder tbaaBuilder;
+  std::unique_ptr<TBAABuilder> tbaaBuilder;
 };
 
 } // namespace fir
 
 #endif // FORTRAN_OPTIMIZER_CODEGEN_TYPECONVERTER_H

flang/lib/Optimizer/CodeGen/TypeConverter.cpp

: mlir::LLVMTypeConverter(module.getContext(),
                                     module.getContext());
                                 options.useOpaquePointers = false;
                                 return options;
                               }()),
       kindMapping(getKindMapping(module)),
       specifics(CodeGenSpecifics::get(module.getContext(),
                                       getTargetTriple(module),
                                       getKindMapping(module))),
-      tbaaBuilder(module->getContext(), applyTBAA) {
+      tbaaBuilder(
+          std::make_unique<TBAABuilder>(module->getContext(), applyTBAA)) {
   LLVM_DEBUG(llvm::dbgs() << "FIR type converter\n");
 
   // Each conversion should return a value of type mlir::Type.
   addConversion([&](BoxType box) { return convertBoxType(box); });
   addConversion([&](BoxCharType boxchar) {
     LLVM_DEBUG(llvm::dbgs() << "type convert: " << boxchar << '\n');
     return convertType(specifics->boxcharMemoryType(boxchar.getEleTy()));
   });
return mlir::LLVM::LLVMPointerType::get(
       mlir::IntegerType::get(&getContext(), 8));
 }
 
 // Relay TBAA tag attachment to TBAABuilder.
 void LLVMTypeConverter::attachTBAATag(mlir::LLVM::AliasAnalysisOpInterface op,
                                       mlir::Type baseFIRType,
                                       mlir::Type accessFIRType,
                                       mlir::LLVM::GEPOp gep) {
-  tbaaBuilder.attachTBAATag(op, baseFIRType, accessFIRType, gep);
+  tbaaBuilder->attachTBAATag(op, baseFIRType, accessFIRType, gep);
 }
 
 } // namespace fir