1//===--- CGVTables.h - Emit LLVM Code for C++ vtables -----------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This contains code dealing with C++ code generation of virtual tables.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_CLANG_LIB_CODEGEN_CGVTABLES_H
14#define LLVM_CLANG_LIB_CODEGEN_CGVTABLES_H
15
16#include "clang/AST/BaseSubobject.h"
17#include "clang/AST/CharUnits.h"
18#include "clang/AST/GlobalDecl.h"
19#include "clang/AST/VTableBuilder.h"
20#include "clang/Basic/ABI.h"
21#include "llvm/ADT/DenseMap.h"
22#include "llvm/IR/GlobalVariable.h"
23
24namespace clang {
25  class CXXRecordDecl;
26
27namespace CodeGen {
28  class CodeGenModule;
29  class ConstantArrayBuilder;
30  class ConstantStructBuilder;
31
32class CodeGenVTables {
33  CodeGenModule &CGM;
34
35  VTableContextBase *VTContext;
36
37  /// VTableAddressPointsMapTy - Address points for a single vtable.
38  typedef VTableLayout::AddressPointsMapTy VTableAddressPointsMapTy;
39
40  typedef std::pair<const CXXRecordDecl *, BaseSubobject> BaseSubobjectPairTy;
41  typedef llvm::DenseMap<BaseSubobjectPairTy, uint64_t> SubVTTIndiciesMapTy;
42
43  /// SubVTTIndicies - Contains indices into the various sub-VTTs.
44  SubVTTIndiciesMapTy SubVTTIndicies;
45
46  typedef llvm::DenseMap<BaseSubobjectPairTy, uint64_t>
47    SecondaryVirtualPointerIndicesMapTy;
48
49  /// SecondaryVirtualPointerIndices - Contains the secondary virtual pointer
50  /// indices.
51  SecondaryVirtualPointerIndicesMapTy SecondaryVirtualPointerIndices;
52
53  /// Cache for the pure virtual member call function.
54  llvm::Constant *PureVirtualFn = nullptr;
55
56  /// Cache for the deleted virtual member call function.
57  llvm::Constant *DeletedVirtualFn = nullptr;
58
59  /// Get the address of a thunk and emit it if necessary.
60  llvm::Constant *maybeEmitThunk(GlobalDecl GD,
61                                 const ThunkInfo &ThunkAdjustments,
62                                 bool ForVTable);
63
64  void addVTableComponent(ConstantArrayBuilder &builder,
65                          const VTableLayout &layout, unsigned componentIndex,
66                          llvm::Constant *rtti, unsigned &nextVTableThunkIndex,
67                          unsigned vtableAddressPoint,
68                          bool vtableHasLocalLinkage);
69
70  /// Add a 32-bit offset to a component relative to the vtable when using the
71  /// relative vtables ABI. The array builder points to the start of the vtable.
72  void addRelativeComponent(ConstantArrayBuilder &builder,
73                            llvm::Constant *component,
74                            unsigned vtableAddressPoint,
75                            bool vtableHasLocalLinkage,
76                            bool isCompleteDtor) const;
77
78  /// Create a dso_local stub that will be used for a relative reference in the
79  /// relative vtable layout. This stub will just be a tail call to the original
80  /// function and propagate any function attributes from the original. If the
81  /// original function is already dso_local, the original is returned instead
82  /// and a stub is not created.
83  llvm::Function *
84  getOrCreateRelativeStub(llvm::Function *func,
85                          llvm::GlobalValue::LinkageTypes stubLinkage,
86                          bool isCompleteDtor) const;
87
88  bool useRelativeLayout() const;
89
90  llvm::Type *getVTableComponentType() const;
91
92public:
93  /// Add vtable components for the given vtable layout to the given
94  /// global initializer.
95  void createVTableInitializer(ConstantStructBuilder &builder,
96                               const VTableLayout &layout, llvm::Constant *rtti,
97                               bool vtableHasLocalLinkage);
98
99  CodeGenVTables(CodeGenModule &CGM);
100
101  ItaniumVTableContext &getItaniumVTableContext() {
102    return *cast<ItaniumVTableContext>(VTContext);
103  }
104
105  MicrosoftVTableContext &getMicrosoftVTableContext() {
106    return *cast<MicrosoftVTableContext>(VTContext);
107  }
108
109  /// getSubVTTIndex - Return the index of the sub-VTT for the base class of the
110  /// given record decl.
111  uint64_t getSubVTTIndex(const CXXRecordDecl *RD, BaseSubobject Base);
112
113  /// getSecondaryVirtualPointerIndex - Return the index in the VTT where the
114  /// virtual pointer for the given subobject is located.
115  uint64_t getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
116                                           BaseSubobject Base);
117
118  /// GenerateConstructionVTable - Generate a construction vtable for the given
119  /// base subobject.
120  llvm::GlobalVariable *
121  GenerateConstructionVTable(const CXXRecordDecl *RD, const BaseSubobject &Base,
122                             bool BaseIsVirtual,
123                             llvm::GlobalVariable::LinkageTypes Linkage,
124                             VTableAddressPointsMapTy& AddressPoints);
125
126
127  /// GetAddrOfVTT - Get the address of the VTT for the given record decl.
128  llvm::GlobalVariable *GetAddrOfVTT(const CXXRecordDecl *RD);
129
130  /// EmitVTTDefinition - Emit the definition of the given vtable.
131  void EmitVTTDefinition(llvm::GlobalVariable *VTT,
132                         llvm::GlobalVariable::LinkageTypes Linkage,
133                         const CXXRecordDecl *RD);
134
135  /// EmitThunks - Emit the associated thunks for the given global decl.
136  void EmitThunks(GlobalDecl GD);
137
138  /// GenerateClassData - Generate all the class data required to be
139  /// generated upon definition of a KeyFunction.  This includes the
140  /// vtable, the RTTI data structure (if RTTI is enabled) and the VTT
141  /// (if the class has virtual bases).
142  void GenerateClassData(const CXXRecordDecl *RD);
143
144  bool isVTableExternal(const CXXRecordDecl *RD);
145
146  /// Returns the type of a vtable with the given layout. Normally a struct of
147  /// arrays of pointers, with one struct element for each vtable in the vtable
148  /// group.
149  llvm::Type *getVTableType(const VTableLayout &layout);
150
151  /// Generate a public facing alias for the vtable and make the vtable either
152  /// hidden or private. The alias will have the original linkage and visibility
153  /// of the vtable. This is used for cases under the relative vtables ABI
154  /// when a vtable may not be dso_local.
155  void GenerateRelativeVTableAlias(llvm::GlobalVariable *VTable,
156                                   llvm::StringRef AliasNameRef);
157};
158
159} // end namespace CodeGen
160} // end namespace clang
161#endif
162