1 //===--- CGVTT.cpp - Emit LLVM Code for C++ VTTs --------------------------===//
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 VTTs (vtable tables).
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "CodeGenModule.h"
15 #include "CGCXXABI.h"
16 #include "clang/AST/RecordLayout.h"
17 #include "clang/AST/VTTBuilder.h"
18 using namespace clang;
19 using namespace CodeGen;
20
21 static llvm::Constant *
GetAddrOfVTTVTable(CodeGenVTables & CGVT,CodeGenModule & CGM,const CXXRecordDecl * MostDerivedClass,const VTTVTable & VTable,llvm::GlobalVariable::LinkageTypes Linkage,llvm::DenseMap<BaseSubobject,uint64_t> & AddressPoints)22 GetAddrOfVTTVTable(CodeGenVTables &CGVT, CodeGenModule &CGM,
23 const CXXRecordDecl *MostDerivedClass,
24 const VTTVTable &VTable,
25 llvm::GlobalVariable::LinkageTypes Linkage,
26 llvm::DenseMap<BaseSubobject, uint64_t> &AddressPoints) {
27 if (VTable.getBase() == MostDerivedClass) {
28 assert(VTable.getBaseOffset().isZero() &&
29 "Most derived class vtable must have a zero offset!");
30 // This is a regular vtable.
31 return CGM.getCXXABI().getAddrOfVTable(MostDerivedClass, CharUnits());
32 }
33
34 return CGVT.GenerateConstructionVTable(MostDerivedClass,
35 VTable.getBaseSubobject(),
36 VTable.isVirtual(),
37 Linkage,
38 AddressPoints);
39 }
40
41 void
EmitVTTDefinition(llvm::GlobalVariable * VTT,llvm::GlobalVariable::LinkageTypes Linkage,const CXXRecordDecl * RD)42 CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
43 llvm::GlobalVariable::LinkageTypes Linkage,
44 const CXXRecordDecl *RD) {
45 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true);
46
47 llvm::Type *Int8PtrTy = CGM.Int8PtrTy, *Int64Ty = CGM.Int64Ty;
48 llvm::ArrayType *ArrayType =
49 llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
50
51 SmallVector<llvm::Constant *, 8> VTables;
52 SmallVector<VTableAddressPointsMapTy, 8> VTableAddressPoints;
53 for (const VTTVTable *i = Builder.getVTTVTables().begin(),
54 *e = Builder.getVTTVTables().end(); i != e; ++i) {
55 VTableAddressPoints.push_back(VTableAddressPointsMapTy());
56 VTables.push_back(GetAddrOfVTTVTable(*this, CGM, RD, *i, Linkage,
57 VTableAddressPoints.back()));
58 }
59
60 SmallVector<llvm::Constant *, 8> VTTComponents;
61 for (const VTTComponent *i = Builder.getVTTComponents().begin(),
62 *e = Builder.getVTTComponents().end(); i != e; ++i) {
63 const VTTVTable &VTTVT = Builder.getVTTVTables()[i->VTableIndex];
64 llvm::Constant *VTable = VTables[i->VTableIndex];
65 uint64_t AddressPoint;
66 if (VTTVT.getBase() == RD) {
67 // Just get the address point for the regular vtable.
68 AddressPoint =
69 getItaniumVTableContext().getVTableLayout(RD).getAddressPoint(
70 i->VTableBase);
71 assert(AddressPoint != 0 && "Did not find vtable address point!");
72 } else {
73 AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
74 assert(AddressPoint != 0 && "Did not find ctor vtable address point!");
75 }
76
77 llvm::Value *Idxs[] = {
78 llvm::ConstantInt::get(Int64Ty, 0),
79 llvm::ConstantInt::get(Int64Ty, AddressPoint)
80 };
81
82 llvm::Constant *Init =
83 llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Idxs);
84
85 Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
86
87 VTTComponents.push_back(Init);
88 }
89
90 llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
91
92 VTT->setInitializer(Init);
93
94 // Set the correct linkage.
95 VTT->setLinkage(Linkage);
96
97 // Set the right visibility.
98 CGM.setGlobalVisibility(VTT, RD);
99 }
100
GetAddrOfVTT(const CXXRecordDecl * RD)101 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
102 assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
103
104 SmallString<256> OutName;
105 llvm::raw_svector_ostream Out(OutName);
106 cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
107 .mangleCXXVTT(RD, Out);
108 Out.flush();
109 StringRef Name = OutName.str();
110
111 // This will also defer the definition of the VTT.
112 (void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());
113
114 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
115
116 llvm::ArrayType *ArrayType =
117 llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
118
119 llvm::GlobalVariable *GV =
120 CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType,
121 llvm::GlobalValue::ExternalLinkage);
122 GV->setUnnamedAddr(true);
123 return GV;
124 }
125
getSubVTTIndex(const CXXRecordDecl * RD,BaseSubobject Base)126 uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,
127 BaseSubobject Base) {
128 BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
129
130 SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
131 if (I != SubVTTIndicies.end())
132 return I->second;
133
134 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
135
136 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
137 Builder.getSubVTTIndicies().begin(),
138 E = Builder.getSubVTTIndicies().end(); I != E; ++I) {
139 // Insert all indices.
140 BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);
141
142 SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
143 }
144
145 I = SubVTTIndicies.find(ClassSubobjectPair);
146 assert(I != SubVTTIndicies.end() && "Did not find index!");
147
148 return I->second;
149 }
150
151 uint64_t
getSecondaryVirtualPointerIndex(const CXXRecordDecl * RD,BaseSubobject Base)152 CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
153 BaseSubobject Base) {
154 SecondaryVirtualPointerIndicesMapTy::iterator I =
155 SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
156
157 if (I != SecondaryVirtualPointerIndices.end())
158 return I->second;
159
160 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
161
162 // Insert all secondary vpointer indices.
163 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
164 Builder.getSecondaryVirtualPointerIndices().begin(),
165 E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {
166 std::pair<const CXXRecordDecl *, BaseSubobject> Pair =
167 std::make_pair(RD, I->first);
168
169 SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
170 }
171
172 I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
173 assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");
174
175 return I->second;
176 }
177
178