195 lines · cpp
1//===--- CGVTT.cpp - Emit LLVM Code for C++ VTTs --------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This contains code dealing with C++ code generation of VTTs (vtable tables).10//11//===----------------------------------------------------------------------===//12 13#include "CodeGenModule.h"14#include "CGCXXABI.h"15#include "clang/AST/RecordLayout.h"16#include "clang/AST/VTTBuilder.h"17using namespace clang;18using namespace CodeGen;19 20static llvm::GlobalVariable *21GetAddrOfVTTVTable(CodeGenVTables &CGVT, CodeGenModule &CGM,22 const CXXRecordDecl *MostDerivedClass,23 const VTTVTable &VTable,24 llvm::GlobalVariable::LinkageTypes Linkage,25 VTableLayout::AddressPointsMapTy &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 CGM.getCXXABI().getAddrOfVTable(MostDerivedClass, CharUnits());31 }32 33 return CGVT.GenerateConstructionVTable(MostDerivedClass,34 VTable.getBaseSubobject(),35 VTable.isVirtual(),36 Linkage,37 AddressPoints);38}39 40void41CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,42 llvm::GlobalVariable::LinkageTypes Linkage,43 const CXXRecordDecl *RD) {44 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true);45 llvm::ArrayType *ArrayType = llvm::ArrayType::get(46 CGM.GlobalsInt8PtrTy, Builder.getVTTComponents().size());47 48 SmallVector<llvm::GlobalVariable *, 8> VTables;49 SmallVector<VTableAddressPointsMapTy, 8> VTableAddressPoints;50 for (const VTTVTable *i = Builder.getVTTVTables().begin(),51 *e = Builder.getVTTVTables().end(); i != e; ++i) {52 VTableAddressPoints.push_back(VTableAddressPointsMapTy());53 VTables.push_back(GetAddrOfVTTVTable(*this, CGM, RD, *i, Linkage,54 VTableAddressPoints.back()));55 }56 57 SmallVector<llvm::Constant *, 8> VTTComponents;58 for (const VTTComponent *i = Builder.getVTTComponents().begin(),59 *e = Builder.getVTTComponents().end(); i != e; ++i) {60 const VTTVTable &VTTVT = Builder.getVTTVTables()[i->VTableIndex];61 llvm::GlobalVariable *VTable = VTables[i->VTableIndex];62 VTableLayout::AddressPointLocation AddressPoint;63 if (VTTVT.getBase() == RD) {64 // Just get the address point for the regular vtable.65 AddressPoint =66 getItaniumVTableContext().getVTableLayout(RD).getAddressPoint(67 i->VTableBase);68 } else {69 AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);70 assert(AddressPoint.AddressPointIndex != 0 &&71 "Did not find ctor vtable address point!");72 }73 74 llvm::Value *Idxs[] = {75 llvm::ConstantInt::get(CGM.Int32Ty, 0),76 llvm::ConstantInt::get(CGM.Int32Ty, AddressPoint.VTableIndex),77 llvm::ConstantInt::get(CGM.Int32Ty, AddressPoint.AddressPointIndex),78 };79 80 // Add inrange attribute to indicate that only the VTableIndex can be81 // accessed.82 unsigned ComponentSize =83 CGM.getDataLayout().getTypeAllocSize(getVTableComponentType());84 unsigned VTableSize = CGM.getDataLayout().getTypeAllocSize(85 cast<llvm::StructType>(VTable->getValueType())86 ->getElementType(AddressPoint.VTableIndex));87 unsigned Offset = ComponentSize * AddressPoint.AddressPointIndex;88 llvm::ConstantRange InRange(89 llvm::APInt(32, (int)-Offset, true),90 llvm::APInt(32, (int)(VTableSize - Offset), true));91 llvm::Constant *Init = llvm::ConstantExpr::getGetElementPtr(92 VTable->getValueType(), VTable, Idxs, /*InBounds=*/true, InRange);93 94 if (const auto &Schema =95 CGM.getCodeGenOpts().PointerAuth.CXXVTTVTablePointers)96 Init = CGM.getConstantSignedPointer(Init, Schema, nullptr, GlobalDecl(),97 QualType());98 99 VTTComponents.push_back(Init);100 }101 102 llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);103 104 VTT->setInitializer(Init);105 106 // Set the correct linkage.107 VTT->setLinkage(Linkage);108 109 if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())110 VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));111 112 // Set the visibility. This will already have been set on the VTT declaration.113 // Set it again, now that we have a definition, as the implicit visibility can114 // apply differently to definitions.115 CGM.setGVProperties(VTT, RD);116}117 118llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {119 assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");120 121 SmallString<256> OutName;122 llvm::raw_svector_ostream Out(OutName);123 cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())124 .mangleCXXVTT(RD, Out);125 StringRef Name = OutName.str();126 127 // This will also defer the definition of the VTT.128 (void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());129 130 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);131 132 llvm::ArrayType *ArrayType = llvm::ArrayType::get(133 CGM.GlobalsInt8PtrTy, Builder.getVTTComponents().size());134 llvm::Align Align = CGM.getDataLayout().getABITypeAlign(CGM.GlobalsInt8PtrTy);135 136 llvm::GlobalVariable *GV = CGM.CreateOrReplaceCXXRuntimeVariable(137 Name, ArrayType, llvm::GlobalValue::ExternalLinkage, Align);138 GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);139 CGM.setGVProperties(GV, RD);140 return GV;141}142 143uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,144 BaseSubobject Base) {145 BaseSubobjectPairTy ClassSubobjectPair(RD, Base);146 147 SubVTTIndicesMapTy::iterator I = SubVTTIndices.find(ClassSubobjectPair);148 if (I != SubVTTIndices.end())149 return I->second;150 151 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);152 153 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator154 I = Builder.getSubVTTIndices().begin(),155 E = Builder.getSubVTTIndices().end();156 I != E; ++I) {157 // Insert all indices.158 BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);159 160 SubVTTIndices.insert(std::make_pair(ClassSubobjectPair, I->second));161 }162 163 I = SubVTTIndices.find(ClassSubobjectPair);164 assert(I != SubVTTIndices.end() && "Did not find index!");165 166 return I->second;167}168 169uint64_t170CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,171 BaseSubobject Base) {172 SecondaryVirtualPointerIndicesMapTy::iterator I =173 SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));174 175 if (I != SecondaryVirtualPointerIndices.end())176 return I->second;177 178 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);179 180 // Insert all secondary vpointer indices.181 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =182 Builder.getSecondaryVirtualPointerIndices().begin(),183 E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {184 std::pair<const CXXRecordDecl *, BaseSubobject> Pair =185 std::make_pair(RD, I->first);186 187 SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));188 }189 190 I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));191 assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");192 193 return I->second;194}195