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