1 //===--- CGVTables.h - Emit LLVM Code for C++ vtables -----------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This contains code dealing with C++ code generation of virtual tables.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_LIB_CODEGEN_CGVTABLES_H
15 #define LLVM_CLANG_LIB_CODEGEN_CGVTABLES_H
16 
17 #include "clang/AST/BaseSubobject.h"
18 #include "clang/AST/CharUnits.h"
19 #include "clang/AST/GlobalDecl.h"
20 #include "clang/AST/VTableBuilder.h"
21 #include "clang/Basic/ABI.h"
22 #include "llvm/ADT/DenseMap.h"
23 #include "llvm/IR/GlobalVariable.h"
24 
25 namespace clang {
26   class CXXRecordDecl;
27 
28 namespace CodeGen {
29   class CodeGenModule;
30   class ConstantArrayBuilder;
31   class ConstantStructBuilder;
32 
33 class CodeGenVTables {
34   CodeGenModule &CGM;
35 
36   VTableContextBase *VTContext;
37 
38   /// VTableAddressPointsMapTy - Address points for a single vtable.
39   typedef VTableLayout::AddressPointsMapTy VTableAddressPointsMapTy;
40 
41   typedef std::pair<const CXXRecordDecl *, BaseSubobject> BaseSubobjectPairTy;
42   typedef llvm::DenseMap<BaseSubobjectPairTy, uint64_t> SubVTTIndiciesMapTy;
43 
44   /// SubVTTIndicies - Contains indices into the various sub-VTTs.
45   SubVTTIndiciesMapTy SubVTTIndicies;
46 
47   typedef llvm::DenseMap<BaseSubobjectPairTy, uint64_t>
48     SecondaryVirtualPointerIndicesMapTy;
49 
50   /// SecondaryVirtualPointerIndices - Contains the secondary virtual pointer
51   /// indices.
52   SecondaryVirtualPointerIndicesMapTy SecondaryVirtualPointerIndices;
53 
54   /// Cache for the pure virtual member call function.
55   llvm::Constant *PureVirtualFn = nullptr;
56 
57   /// Cache for the deleted virtual member call function.
58   llvm::Constant *DeletedVirtualFn = nullptr;
59 
60   /// emitThunk - Emit a single thunk.
61   void emitThunk(GlobalDecl GD, const ThunkInfo &Thunk, bool ForVTable);
62 
63   /// maybeEmitThunkForVTable - Emit the given thunk for the vtable if needed by
64   /// the ABI.
65   void maybeEmitThunkForVTable(GlobalDecl GD, const ThunkInfo &Thunk);
66 
67   void addVTableComponent(ConstantArrayBuilder &builder,
68                           const VTableLayout &layout, unsigned idx,
69                           llvm::Constant *rtti,
70                           unsigned &nextVTableThunkIndex);
71 
72 public:
73   /// Add vtable components for the given vtable layout to the given
74   /// global initializer.
75   void createVTableInitializer(ConstantStructBuilder &builder,
76                                const VTableLayout &layout,
77                                llvm::Constant *rtti);
78 
79   CodeGenVTables(CodeGenModule &CGM);
80 
81   ItaniumVTableContext &getItaniumVTableContext() {
82     return *cast<ItaniumVTableContext>(VTContext);
83   }
84 
85   MicrosoftVTableContext &getMicrosoftVTableContext() {
86     return *cast<MicrosoftVTableContext>(VTContext);
87   }
88 
89   /// getSubVTTIndex - Return the index of the sub-VTT for the base class of the
90   /// given record decl.
91   uint64_t getSubVTTIndex(const CXXRecordDecl *RD, BaseSubobject Base);
92 
93   /// getSecondaryVirtualPointerIndex - Return the index in the VTT where the
94   /// virtual pointer for the given subobject is located.
95   uint64_t getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
96                                            BaseSubobject Base);
97 
98   /// GenerateConstructionVTable - Generate a construction vtable for the given
99   /// base subobject.
100   llvm::GlobalVariable *
101   GenerateConstructionVTable(const CXXRecordDecl *RD, const BaseSubobject &Base,
102                              bool BaseIsVirtual,
103                              llvm::GlobalVariable::LinkageTypes Linkage,
104                              VTableAddressPointsMapTy& AddressPoints);
105 
106 
107   /// GetAddrOfVTT - Get the address of the VTT for the given record decl.
108   llvm::GlobalVariable *GetAddrOfVTT(const CXXRecordDecl *RD);
109 
110   /// EmitVTTDefinition - Emit the definition of the given vtable.
111   void EmitVTTDefinition(llvm::GlobalVariable *VTT,
112                          llvm::GlobalVariable::LinkageTypes Linkage,
113                          const CXXRecordDecl *RD);
114 
115   /// EmitThunks - Emit the associated thunks for the given global decl.
116   void EmitThunks(GlobalDecl GD);
117 
118   /// GenerateClassData - Generate all the class data required to be
119   /// generated upon definition of a KeyFunction.  This includes the
120   /// vtable, the RTTI data structure (if RTTI is enabled) and the VTT
121   /// (if the class has virtual bases).
122   void GenerateClassData(const CXXRecordDecl *RD);
123 
124   bool isVTableExternal(const CXXRecordDecl *RD);
125 
126   /// Returns the type of a vtable with the given layout. Normally a struct of
127   /// arrays of pointers, with one struct element for each vtable in the vtable
128   /// group.
129   llvm::Type *getVTableType(const VTableLayout &layout);
130 };
131 
132 } // end namespace CodeGen
133 } // end namespace clang
134 #endif
135