1 //===--- CGVTT.cpp - Emit LLVM Code for C++ VTTs --------------------------===//
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-exception
7 //===----------------------------------------------------------------------===//
9 // This contains code dealing with C++ code generation of VTTs (vtable tables).
11 //===----------------------------------------------------------------------===//
13 #include "CodeGenModule.h"
15 #include "clang/AST/RecordLayout.h"
16 #include "clang/AST/VTTBuilder.h"
17 using namespace clang;
18 using namespace CodeGen;
20 static llvm::GlobalVariable *
21 GetAddrOfVTTVTable(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());
33 return CGVT.GenerateConstructionVTable(MostDerivedClass,
34 VTable.getBaseSubobject(),
41 CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
42 llvm::GlobalVariable::LinkageTypes Linkage,
43 const CXXRecordDecl *RD) {
44 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true);
46 llvm::Type *Int8PtrTy = CGM.Int8PtrTy, *Int32Ty = CGM.Int32Ty;
47 llvm::ArrayType *ArrayType =
48 llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
50 SmallVector<llvm::GlobalVariable *, 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, CGM, RD, *i, Linkage,
56 VTableAddressPoints.back()));
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::GlobalVariable *VTable = VTables[i->VTableIndex];
64 VTableLayout::AddressPointLocation AddressPoint;
65 if (VTTVT.getBase() == RD) {
66 // Just get the address point for the regular vtable.
68 getItaniumVTableContext().getVTableLayout(RD).getAddressPoint(
71 AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
72 assert(AddressPoint.AddressPointIndex != 0 &&
73 "Did not find ctor vtable address point!");
76 llvm::Value *Idxs[] = {
77 llvm::ConstantInt::get(Int32Ty, 0),
78 llvm::ConstantInt::get(Int32Ty, AddressPoint.VTableIndex),
79 llvm::ConstantInt::get(Int32Ty, AddressPoint.AddressPointIndex),
82 llvm::Constant *Init = llvm::ConstantExpr::getGetElementPtr(
83 VTable->getValueType(), VTable, Idxs, /*InBounds=*/true,
86 Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
88 VTTComponents.push_back(Init);
91 llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
93 VTT->setInitializer(Init);
95 // Set the correct linkage.
96 VTT->setLinkage(Linkage);
98 if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
99 VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
101 // Set the right visibility.
102 CGM.setGVProperties(VTT, RD);
105 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
106 assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
108 SmallString<256> OutName;
109 llvm::raw_svector_ostream Out(OutName);
110 cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
111 .mangleCXXVTT(RD, Out);
112 StringRef Name = OutName.str();
114 // This will also defer the definition of the VTT.
115 (void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());
117 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
119 llvm::ArrayType *ArrayType =
120 llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
121 unsigned Align = CGM.getDataLayout().getABITypeAlignment(CGM.Int8PtrTy);
123 llvm::GlobalVariable *GV = CGM.CreateOrReplaceCXXRuntimeVariable(
124 Name, ArrayType, llvm::GlobalValue::ExternalLinkage, Align);
125 GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
129 uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,
130 BaseSubobject Base) {
131 BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
133 SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
134 if (I != SubVTTIndicies.end())
137 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
139 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
140 Builder.getSubVTTIndicies().begin(),
141 E = Builder.getSubVTTIndicies().end(); I != E; ++I) {
142 // Insert all indices.
143 BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);
145 SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
148 I = SubVTTIndicies.find(ClassSubobjectPair);
149 assert(I != SubVTTIndicies.end() && "Did not find index!");
155 CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
156 BaseSubobject Base) {
157 SecondaryVirtualPointerIndicesMapTy::iterator I =
158 SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
160 if (I != SecondaryVirtualPointerIndices.end())
163 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
165 // Insert all secondary vpointer indices.
166 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
167 Builder.getSecondaryVirtualPointerIndices().begin(),
168 E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {
169 std::pair<const CXXRecordDecl *, BaseSubobject> Pair =
170 std::make_pair(RD, I->first);
172 SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
175 I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
176 assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");