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::GlobalVariable *
GetAddrOfVTTVTable(CodeGenVTables & CGVT,CodeGenModule & CGM,const CXXRecordDecl * MostDerivedClass,const VTTVTable & VTable,llvm::GlobalVariable::LinkageTypes Linkage,VTableLayout::AddressPointsMapTy & AddressPoints)22 GetAddrOfVTTVTable(CodeGenVTables &CGVT, CodeGenModule &CGM,
23 const CXXRecordDecl *MostDerivedClass,
24 const VTTVTable &VTable,
25 llvm::GlobalVariable::LinkageTypes Linkage,
26 VTableLayout::AddressPointsMapTy &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, *Int32Ty = CGM.Int32Ty;
48 llvm::ArrayType *ArrayType =
49 llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
50
51 SmallVector<llvm::GlobalVariable *, 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::GlobalVariable *VTable = VTables[i->VTableIndex];
65 VTableLayout::AddressPointLocation 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 } else {
72 AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
73 assert(AddressPoint.AddressPointIndex != 0 &&
74 "Did not find ctor vtable address point!");
75 }
76
77 llvm::Value *Idxs[] = {
78 llvm::ConstantInt::get(Int32Ty, 0),
79 llvm::ConstantInt::get(Int32Ty, AddressPoint.VTableIndex),
80 llvm::ConstantInt::get(Int32Ty, AddressPoint.AddressPointIndex),
81 };
82
83 llvm::Constant *Init = llvm::ConstantExpr::getGetElementPtr(
84 VTable->getValueType(), VTable, Idxs, /*InBounds=*/true,
85 /*InRangeIndex=*/1);
86
87 Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
88
89 VTTComponents.push_back(Init);
90 }
91
92 llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
93
94 VTT->setInitializer(Init);
95
96 // Set the correct linkage.
97 VTT->setLinkage(Linkage);
98
99 if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
100 VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
101
102 // Set the right visibility.
103 CGM.setGVProperties(VTT, RD);
104 }
105
GetAddrOfVTT(const CXXRecordDecl * RD)106 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
107 assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
108
109 SmallString<256> OutName;
110 llvm::raw_svector_ostream Out(OutName);
111 cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
112 .mangleCXXVTT(RD, Out);
113 StringRef Name = OutName.str();
114
115 // This will also defer the definition of the VTT.
116 (void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());
117
118 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
119
120 llvm::ArrayType *ArrayType =
121 llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
122
123 llvm::GlobalVariable *GV =
124 CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType,
125 llvm::GlobalValue::ExternalLinkage);
126 GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
127 return GV;
128 }
129
getSubVTTIndex(const CXXRecordDecl * RD,BaseSubobject Base)130 uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,
131 BaseSubobject Base) {
132 BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
133
134 SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
135 if (I != SubVTTIndicies.end())
136 return I->second;
137
138 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
139
140 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
141 Builder.getSubVTTIndicies().begin(),
142 E = Builder.getSubVTTIndicies().end(); I != E; ++I) {
143 // Insert all indices.
144 BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);
145
146 SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
147 }
148
149 I = SubVTTIndicies.find(ClassSubobjectPair);
150 assert(I != SubVTTIndicies.end() && "Did not find index!");
151
152 return I->second;
153 }
154
155 uint64_t
getSecondaryVirtualPointerIndex(const CXXRecordDecl * RD,BaseSubobject Base)156 CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
157 BaseSubobject Base) {
158 SecondaryVirtualPointerIndicesMapTy::iterator I =
159 SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
160
161 if (I != SecondaryVirtualPointerIndices.end())
162 return I->second;
163
164 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
165
166 // Insert all secondary vpointer indices.
167 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
168 Builder.getSecondaryVirtualPointerIndices().begin(),
169 E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {
170 std::pair<const CXXRecordDecl *, BaseSubobject> Pair =
171 std::make_pair(RD, I->first);
172
173 SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
174 }
175
176 I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
177 assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");
178
179 return I->second;
180 }
181