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" 18using namespace clang; 19using namespace CodeGen; 20 21static llvm::Constant * 22GetAddrOfVTTVTable(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 41void 42CodeGenVTables::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 ItaniumVTContext.getVTableLayout(RD).getAddressPoint(i->VTableBase); 70 assert(AddressPoint != 0 && "Did not find vtable address point!"); 71 } else { 72 AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase); 73 assert(AddressPoint != 0 && "Did not find ctor vtable address point!"); 74 } 75 76 llvm::Value *Idxs[] = { 77 llvm::ConstantInt::get(Int64Ty, 0), 78 llvm::ConstantInt::get(Int64Ty, AddressPoint) 79 }; 80 81 llvm::Constant *Init = 82 llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Idxs); 83 84 Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy); 85 86 VTTComponents.push_back(Init); 87 } 88 89 llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents); 90 91 VTT->setInitializer(Init); 92 93 // Set the correct linkage. 94 VTT->setLinkage(Linkage); 95 96 // Set the right visibility. 97 CGM.setTypeVisibility(VTT, RD, CodeGenModule::TVK_ForVTT); 98} 99 100llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) { 101 assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT"); 102 103 SmallString<256> OutName; 104 llvm::raw_svector_ostream Out(OutName); 105 cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext()) 106 .mangleCXXVTT(RD, Out); 107 Out.flush(); 108 StringRef Name = OutName.str(); 109 110 // This will also defer the definition of the VTT. 111 (void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits()); 112 113 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false); 114 115 llvm::ArrayType *ArrayType = 116 llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size()); 117 118 llvm::GlobalVariable *GV = 119 CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType, 120 llvm::GlobalValue::ExternalLinkage); 121 GV->setUnnamedAddr(true); 122 return GV; 123} 124 125uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD, 126 BaseSubobject Base) { 127 BaseSubobjectPairTy ClassSubobjectPair(RD, Base); 128 129 SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair); 130 if (I != SubVTTIndicies.end()) 131 return I->second; 132 133 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false); 134 135 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I = 136 Builder.getSubVTTIndicies().begin(), 137 E = Builder.getSubVTTIndicies().end(); I != E; ++I) { 138 // Insert all indices. 139 BaseSubobjectPairTy ClassSubobjectPair(RD, I->first); 140 141 SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second)); 142 } 143 144 I = SubVTTIndicies.find(ClassSubobjectPair); 145 assert(I != SubVTTIndicies.end() && "Did not find index!"); 146 147 return I->second; 148} 149 150uint64_t 151CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD, 152 BaseSubobject Base) { 153 SecondaryVirtualPointerIndicesMapTy::iterator I = 154 SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base)); 155 156 if (I != SecondaryVirtualPointerIndices.end()) 157 return I->second; 158 159 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false); 160 161 // Insert all secondary vpointer indices. 162 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I = 163 Builder.getSecondaryVirtualPointerIndices().begin(), 164 E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) { 165 std::pair<const CXXRecordDecl *, BaseSubobject> Pair = 166 std::make_pair(RD, I->first); 167 168 SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second)); 169 } 170 171 I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base)); 172 assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!"); 173 174 return I->second; 175} 176 177