//===--- CGVTables.h - Emit LLVM Code for C++ vtables -----------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This contains code dealing with C++ code generation of virtual tables.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_LIB_CODEGEN_CGVTABLES_H

#define LLVM_CLANG_LIB_CODEGEN_CGVTABLES_H

#include "clang/AST/BaseSubobject.h"

#include "clang/AST/CharUnits.h"

#include "clang/AST/GlobalDecl.h"

#include "clang/AST/VTableBuilder.h"

#include "clang/Basic/ABI.h"

#include "llvm/ADT/DenseMap.h"

#include "llvm/IR/GlobalVariable.h"

namespace clang {

  class CXXRecordDecl;

namespace CodeGen {

  class CodeGenModule;

  class ConstantArrayBuilder;

  class ConstantStructBuilder;

class CodeGenVTables {

  CodeGenModule &CGM;

  VTableContextBase *VTContext;

  /// VTableAddressPointsMapTy - Address points for a single vtable.

  typedef VTableLayout::AddressPointsMapTy VTableAddressPointsMapTy;

  typedef std::pair<const CXXRecordDecl *, BaseSubobject> BaseSubobjectPairTy;

  typedef llvm::DenseMap<BaseSubobjectPairTy, uint64_t> SubVTTIndiciesMapTy;

  /// SubVTTIndicies - Contains indices into the various sub-VTTs.

  SubVTTIndiciesMapTy SubVTTIndicies;

  typedef llvm::DenseMap<BaseSubobjectPairTy, uint64_t>

    SecondaryVirtualPointerIndicesMapTy;

  /// SecondaryVirtualPointerIndices - Contains the secondary virtual pointer

  /// indices.

  SecondaryVirtualPointerIndicesMapTy SecondaryVirtualPointerIndices;

  /// Cache for the pure virtual member call function.

  llvm::Constant *PureVirtualFn = nullptr;

  /// Cache for the deleted virtual member call function.

  llvm::Constant *DeletedVirtualFn = nullptr;

  /// Get the address of a thunk and emit it if necessary.

  llvm::Constant *maybeEmitThunk(GlobalDecl GD,

                                 const ThunkInfo &ThunkAdjustments,

                                 bool ForVTable);

  void addVTableComponent(ConstantArrayBuilder &builder,

                          const VTableLayout &layout, unsigned componentIndex,

                          llvm::Constant *rtti, unsigned &nextVTableThunkIndex,

                          unsigned vtableAddressPoint,

                          bool vtableHasLocalLinkage);

  /// Add a 32-bit offset to a component relative to the vtable when using the

  /// relative vtables ABI. The array builder points to the start of the vtable.

  void addRelativeComponent(ConstantArrayBuilder &builder,

                            llvm::Constant *component,

                            unsigned vtableAddressPoint,

                            bool vtableHasLocalLinkage,

                            bool isCompleteDtor) const;

  /// Create a dso_local stub that will be used for a relative reference in the

  /// relative vtable layout. This stub will just be a tail call to the original

  /// function and propagate any function attributes from the original. If the

  /// original function is already dso_local, the original is returned instead

  /// and a stub is not created.

  llvm::Function *

  getOrCreateRelativeStub(llvm::Function *func,

                          llvm::GlobalValue::LinkageTypes stubLinkage,

                          bool isCompleteDtor) const;

  bool useRelativeLayout() const;

  llvm::Type *getVTableComponentType() const;

public:

  /// Add vtable components for the given vtable layout to the given

  /// global initializer.

  void createVTableInitializer(ConstantStructBuilder &builder,

                               const VTableLayout &layout, llvm::Constant *rtti,

                               bool vtableHasLocalLinkage);

  CodeGenVTables(CodeGenModule &CGM);

  ItaniumVTableContext &getItaniumVTableContext() {

    return *cast<ItaniumVTableContext>(VTContext);

  }

  MicrosoftVTableContext &getMicrosoftVTableContext() {

    return *cast<MicrosoftVTableContext>(VTContext);

  }

  /// getSubVTTIndex - Return the index of the sub-VTT for the base class of the

  /// given record decl.

  uint64_t getSubVTTIndex(const CXXRecordDecl *RD, BaseSubobject Base);

  /// getSecondaryVirtualPointerIndex - Return the index in the VTT where the

  /// virtual pointer for the given subobject is located.

  uint64_t getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,

                                           BaseSubobject Base);

  /// GenerateConstructionVTable - Generate a construction vtable for the given

  /// base subobject.

  llvm::GlobalVariable *

  GenerateConstructionVTable(const CXXRecordDecl *RD, const BaseSubobject &Base,

                             bool BaseIsVirtual,

                             llvm::GlobalVariable::LinkageTypes Linkage,

                             VTableAddressPointsMapTy& AddressPoints);

  /// GetAddrOfVTT - Get the address of the VTT for the given record decl.

  llvm::GlobalVariable *GetAddrOfVTT(const CXXRecordDecl *RD);

  /// EmitVTTDefinition - Emit the definition of the given vtable.

  void EmitVTTDefinition(llvm::GlobalVariable *VTT,

                         llvm::GlobalVariable::LinkageTypes Linkage,

                         const CXXRecordDecl *RD);

  /// EmitThunks - Emit the associated thunks for the given global decl.

  void EmitThunks(GlobalDecl GD);

  /// GenerateClassData - Generate all the class data required to be

  /// generated upon definition of a KeyFunction.  This includes the

  /// vtable, the RTTI data structure (if RTTI is enabled) and the VTT

  /// (if the class has virtual bases).

  void GenerateClassData(const CXXRecordDecl *RD);

  bool isVTableExternal(const CXXRecordDecl *RD);

  /// Returns the type of a vtable with the given layout. Normally a struct of

  /// arrays of pointers, with one struct element for each vtable in the vtable

  /// group.

  llvm::Type *getVTableType(const VTableLayout &layout);

  /// Generate a public facing alias for the vtable and make the vtable either

  /// hidden or private. The alias will have the original linkage and visibility

  /// of the vtable. This is used for cases under the relative vtables ABI

  /// when a vtable may not be dso_local.

  void GenerateRelativeVTableAlias(llvm::GlobalVariable *VTable,

                                   llvm::StringRef AliasNameRef);

};

} // end namespace CodeGen

} // end namespace clang

#endif