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 
24 namespace clang {
25   class CXXRecordDecl;
26 
27 namespace CodeGen {
28   class CodeGenModule;
29   class ConstantArrayBuilder;
30   class ConstantStructBuilder;
31 
32 class 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 idx,
66                           llvm::Constant *rtti,
67                           unsigned &nextVTableThunkIndex);
68 
69 public:
70   /// Add vtable components for the given vtable layout to the given
71   /// global initializer.
72   void createVTableInitializer(ConstantStructBuilder &builder,
73                                const VTableLayout &layout,
74                                llvm::Constant *rtti);
75 
76   CodeGenVTables(CodeGenModule &CGM);
77 
78   ItaniumVTableContext &getItaniumVTableContext() {
79     return *cast<ItaniumVTableContext>(VTContext);
80   }
81 
82   MicrosoftVTableContext &getMicrosoftVTableContext() {
83     return *cast<MicrosoftVTableContext>(VTContext);
84   }
85 
86   /// getSubVTTIndex - Return the index of the sub-VTT for the base class of the
87   /// given record decl.
88   uint64_t getSubVTTIndex(const CXXRecordDecl *RD, BaseSubobject Base);
89 
90   /// getSecondaryVirtualPointerIndex - Return the index in the VTT where the
91   /// virtual pointer for the given subobject is located.
92   uint64_t getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
93                                            BaseSubobject Base);
94 
95   /// GenerateConstructionVTable - Generate a construction vtable for the given
96   /// base subobject.
97   llvm::GlobalVariable *
98   GenerateConstructionVTable(const CXXRecordDecl *RD, const BaseSubobject &Base,
99                              bool BaseIsVirtual,
100                              llvm::GlobalVariable::LinkageTypes Linkage,
101                              VTableAddressPointsMapTy& AddressPoints);
102 
103 
104   /// GetAddrOfVTT - Get the address of the VTT for the given record decl.
105   llvm::GlobalVariable *GetAddrOfVTT(const CXXRecordDecl *RD);
106 
107   /// EmitVTTDefinition - Emit the definition of the given vtable.
108   void EmitVTTDefinition(llvm::GlobalVariable *VTT,
109                          llvm::GlobalVariable::LinkageTypes Linkage,
110                          const CXXRecordDecl *RD);
111 
112   /// EmitThunks - Emit the associated thunks for the given global decl.
113   void EmitThunks(GlobalDecl GD);
114 
115   /// GenerateClassData - Generate all the class data required to be
116   /// generated upon definition of a KeyFunction.  This includes the
117   /// vtable, the RTTI data structure (if RTTI is enabled) and the VTT
118   /// (if the class has virtual bases).
119   void GenerateClassData(const CXXRecordDecl *RD);
120 
121   bool isVTableExternal(const CXXRecordDecl *RD);
122 
123   /// Returns the type of a vtable with the given layout. Normally a struct of
124   /// arrays of pointers, with one struct element for each vtable in the vtable
125   /// group.
126   llvm::Type *getVTableType(const VTableLayout &layout);
127 };
128 
129 } // end namespace CodeGen
130 } // end namespace clang
131 #endif
132