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 #define D1(x) 22 23 llvm::Constant *GetAddrOfVTTVTable(CodeGenVTables &CGVT, 24 const CXXRecordDecl *MostDerivedClass, 25 const VTTVTable &VTable, 26 llvm::GlobalVariable::LinkageTypes Linkage, 27 llvm::DenseMap<BaseSubobject, uint64_t> &AddressPoints) { 28 if (VTable.getBase() == MostDerivedClass) { 29 assert(VTable.getBaseOffset().isZero() && 30 "Most derived class vtable must have a zero offset!"); 31 // This is a regular vtable. 32 return CGVT.GetAddrOfVTable(MostDerivedClass); 33 } 34 35 return CGVT.GenerateConstructionVTable(MostDerivedClass, 36 VTable.getBaseSubobject(), 37 VTable.isVirtual(), 38 Linkage, 39 AddressPoints); 40 } 41 42 void 43 CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT, 44 llvm::GlobalVariable::LinkageTypes Linkage, 45 const CXXRecordDecl *RD) { 46 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true); 47 48 llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGM.getLLVMContext()), 49 *Int64Ty = llvm::Type::getInt64Ty(CGM.getLLVMContext()); 50 llvm::ArrayType *ArrayType = 51 llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size()); 52 53 SmallVector<llvm::Constant *, 8> VTables; 54 SmallVector<VTableAddressPointsMapTy, 8> VTableAddressPoints; 55 for (const VTTVTable *i = Builder.getVTTVTables().begin(), 56 *e = Builder.getVTTVTables().end(); i != e; ++i) { 57 VTableAddressPoints.push_back(VTableAddressPointsMapTy()); 58 VTables.push_back(GetAddrOfVTTVTable(*this, RD, *i, Linkage, 59 VTableAddressPoints.back())); 60 } 61 62 SmallVector<llvm::Constant *, 8> VTTComponents; 63 for (const VTTComponent *i = Builder.getVTTComponents().begin(), 64 *e = Builder.getVTTComponents().end(); i != e; ++i) { 65 const VTTVTable &VTTVT = Builder.getVTTVTables()[i->VTableIndex]; 66 llvm::Constant *VTable = VTables[i->VTableIndex]; 67 uint64_t AddressPoint; 68 if (VTTVT.getBase() == RD) { 69 // Just get the address point for the regular vtable. 70 AddressPoint = VTContext.getVTableLayout(RD) 71 .getAddressPoint(i->VTableBase); 72 assert(AddressPoint != 0 && "Did not find vtable address point!"); 73 } else { 74 AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase); 75 assert(AddressPoint != 0 && "Did not find ctor vtable address point!"); 76 } 77 78 llvm::Value *Idxs[] = { 79 llvm::ConstantInt::get(Int64Ty, 0), 80 llvm::ConstantInt::get(Int64Ty, AddressPoint) 81 }; 82 83 llvm::Constant *Init = 84 llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Idxs); 85 86 Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy); 87 88 VTTComponents.push_back(Init); 89 } 90 91 llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents); 92 93 VTT->setInitializer(Init); 94 95 // Set the correct linkage. 96 VTT->setLinkage(Linkage); 97 98 // Set the right visibility. 99 CGM.setTypeVisibility(VTT, RD, CodeGenModule::TVK_ForVTT); 100 } 101 102 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) { 103 assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT"); 104 105 llvm::SmallString<256> OutName; 106 llvm::raw_svector_ostream Out(OutName); 107 CGM.getCXXABI().getMangleContext().mangleCXXVTT(RD, Out); 108 Out.flush(); 109 StringRef Name = OutName.str(); 110 111 // This will also defer the definition of the VTT. 112 (void) GetAddrOfVTable(RD); 113 114 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false); 115 116 llvm::Type *Int8PtrTy = 117 llvm::Type::getInt8PtrTy(CGM.getLLVMContext()); 118 llvm::ArrayType *ArrayType = 119 llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size()); 120 121 llvm::GlobalVariable *GV = 122 CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType, 123 llvm::GlobalValue::ExternalLinkage); 124 GV->setUnnamedAddr(true); 125 return GV; 126 } 127 128 bool CodeGenVTables::needsVTTParameter(GlobalDecl GD) { 129 const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); 130 131 // We don't have any virtual bases, just return early. 132 if (!MD->getParent()->getNumVBases()) 133 return false; 134 135 // Check if we have a base constructor. 136 if (isa<CXXConstructorDecl>(MD) && GD.getCtorType() == Ctor_Base) 137 return true; 138 139 // Check if we have a base destructor. 140 if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base) 141 return true; 142 143 return false; 144 } 145 146 uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD, 147 BaseSubobject Base) { 148 BaseSubobjectPairTy ClassSubobjectPair(RD, Base); 149 150 SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair); 151 if (I != SubVTTIndicies.end()) 152 return I->second; 153 154 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false); 155 156 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I = 157 Builder.getSubVTTIndicies().begin(), 158 E = Builder.getSubVTTIndicies().end(); I != E; ++I) { 159 // Insert all indices. 160 BaseSubobjectPairTy ClassSubobjectPair(RD, I->first); 161 162 SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second)); 163 } 164 165 I = SubVTTIndicies.find(ClassSubobjectPair); 166 assert(I != SubVTTIndicies.end() && "Did not find index!"); 167 168 return I->second; 169 } 170 171 uint64_t 172 CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD, 173 BaseSubobject Base) { 174 SecondaryVirtualPointerIndicesMapTy::iterator I = 175 SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base)); 176 177 if (I != SecondaryVirtualPointerIndices.end()) 178 return I->second; 179 180 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false); 181 182 // Insert all secondary vpointer indices. 183 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I = 184 Builder.getSecondaryVirtualPointerIndices().begin(), 185 E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) { 186 std::pair<const CXXRecordDecl *, BaseSubobject> Pair = 187 std::make_pair(RD, I->first); 188 189 SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second)); 190 } 191 192 I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base)); 193 assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!"); 194 195 return I->second; 196 } 197 198
