1 //===- VTTBuilder.h - C++ VTT layout builder --------------------*- 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 generation of the layout of virtual table
10 // tables (VTT).
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_AST_VTTBUILDER_H
15 #define LLVM_CLANG_AST_VTTBUILDER_H
16 
17 #include "clang/AST/BaseSubobject.h"
18 #include "clang/AST/CharUnits.h"
19 #include "clang/Basic/LLVM.h"
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/PointerIntPair.h"
22 #include "llvm/ADT/SmallPtrSet.h"
23 #include "llvm/ADT/SmallVector.h"
24 #include <cstdint>
25 
26 namespace clang {
27 
28 class ASTContext;
29 class ASTRecordLayout;
30 class CXXRecordDecl;
31 
32 class VTTVTable {
33   llvm::PointerIntPair<const CXXRecordDecl *, 1, bool> BaseAndIsVirtual;
34   CharUnits BaseOffset;
35 
36 public:
37   VTTVTable() = default;
VTTVTable(const CXXRecordDecl * Base,CharUnits BaseOffset,bool BaseIsVirtual)38   VTTVTable(const CXXRecordDecl *Base, CharUnits BaseOffset, bool BaseIsVirtual)
39       : BaseAndIsVirtual(Base, BaseIsVirtual), BaseOffset(BaseOffset) {}
VTTVTable(BaseSubobject Base,bool BaseIsVirtual)40   VTTVTable(BaseSubobject Base, bool BaseIsVirtual)
41       : BaseAndIsVirtual(Base.getBase(), BaseIsVirtual),
42         BaseOffset(Base.getBaseOffset()) {}
43 
getBase()44   const CXXRecordDecl *getBase() const {
45     return BaseAndIsVirtual.getPointer();
46   }
47 
getBaseOffset()48   CharUnits getBaseOffset() const {
49     return BaseOffset;
50   }
51 
isVirtual()52   bool isVirtual() const {
53     return BaseAndIsVirtual.getInt();
54   }
55 
getBaseSubobject()56   BaseSubobject getBaseSubobject() const {
57     return BaseSubobject(getBase(), getBaseOffset());
58   }
59 };
60 
61 struct VTTComponent {
62   uint64_t VTableIndex;
63   BaseSubobject VTableBase;
64 
65   VTTComponent() = default;
VTTComponentVTTComponent66   VTTComponent(uint64_t VTableIndex, BaseSubobject VTableBase)
67      : VTableIndex(VTableIndex), VTableBase(VTableBase) {}
68 };
69 
70 /// Class for building VTT layout information.
71 class VTTBuilder {
72   ASTContext &Ctx;
73 
74   /// The most derived class for which we're building this vtable.
75   const CXXRecordDecl *MostDerivedClass;
76 
77   using VTTVTablesVectorTy = SmallVector<VTTVTable, 64>;
78 
79   /// The VTT vtables.
80   VTTVTablesVectorTy VTTVTables;
81 
82   using VTTComponentsVectorTy = SmallVector<VTTComponent, 64>;
83 
84   /// The VTT components.
85   VTTComponentsVectorTy VTTComponents;
86 
87   /// The AST record layout of the most derived class.
88   const ASTRecordLayout &MostDerivedClassLayout;
89 
90   using VisitedVirtualBasesSetTy = llvm::SmallPtrSet<const CXXRecordDecl *, 4>;
91 
92   using AddressPointsMapTy = llvm::DenseMap<BaseSubobject, uint64_t>;
93 
94   /// The sub-VTT indices for the bases of the most derived class.
95   llvm::DenseMap<BaseSubobject, uint64_t> SubVTTIndicies;
96 
97   /// The secondary virtual pointer indices of all subobjects of
98   /// the most derived class.
99   llvm::DenseMap<BaseSubobject, uint64_t> SecondaryVirtualPointerIndices;
100 
101   /// Whether the VTT builder should generate LLVM IR for the VTT.
102   bool GenerateDefinition;
103 
104   /// Add a vtable pointer to the VTT currently being built.
105   void AddVTablePointer(BaseSubobject Base, uint64_t VTableIndex,
106                         const CXXRecordDecl *VTableClass);
107 
108   /// Lay out the secondary VTTs of the given base subobject.
109   void LayoutSecondaryVTTs(BaseSubobject Base);
110 
111   /// Lay out the secondary virtual pointers for the given base
112   /// subobject.
113   ///
114   /// \param BaseIsMorallyVirtual whether the base subobject is a virtual base
115   /// or a direct or indirect base of a virtual base.
116   void LayoutSecondaryVirtualPointers(BaseSubobject Base,
117                                       bool BaseIsMorallyVirtual,
118                                       uint64_t VTableIndex,
119                                       const CXXRecordDecl *VTableClass,
120                                       VisitedVirtualBasesSetTy &VBases);
121 
122   /// Lay out the secondary virtual pointers for the given base
123   /// subobject.
124   void LayoutSecondaryVirtualPointers(BaseSubobject Base,
125                                       uint64_t VTableIndex);
126 
127   /// Lay out the VTTs for the virtual base classes of the given
128   /// record declaration.
129   void LayoutVirtualVTTs(const CXXRecordDecl *RD,
130                          VisitedVirtualBasesSetTy &VBases);
131 
132   /// Lay out the VTT for the given subobject, including any
133   /// secondary VTTs, secondary virtual pointers and virtual VTTs.
134   void LayoutVTT(BaseSubobject Base, bool BaseIsVirtual);
135 
136 public:
137   VTTBuilder(ASTContext &Ctx, const CXXRecordDecl *MostDerivedClass,
138              bool GenerateDefinition);
139 
140   // Returns a reference to the VTT components.
getVTTComponents()141   const VTTComponentsVectorTy &getVTTComponents() const {
142     return VTTComponents;
143   }
144 
145   // Returns a reference to the VTT vtables.
getVTTVTables()146   const VTTVTablesVectorTy &getVTTVTables() const {
147     return VTTVTables;
148   }
149 
150   /// Returns a reference to the sub-VTT indices.
getSubVTTIndicies()151   const llvm::DenseMap<BaseSubobject, uint64_t> &getSubVTTIndicies() const {
152     return SubVTTIndicies;
153   }
154 
155   /// Returns a reference to the secondary virtual pointer indices.
156   const llvm::DenseMap<BaseSubobject, uint64_t> &
getSecondaryVirtualPointerIndices()157   getSecondaryVirtualPointerIndices() const {
158     return SecondaryVirtualPointerIndices;
159   }
160 };
161 
162 } // namespace clang
163 
164 #endif // LLVM_CLANG_AST_VTTBUILDER_H
165