1 //===--- CGVTT.cpp - Emit LLVM Code for C++ VTTs --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This contains code dealing with C++ code generation of VTTs (vtable tables).
12 //===----------------------------------------------------------------------===//
14 #include "CodeGenModule.h"
16 #include "clang/AST/RecordLayout.h"
17 #include "clang/AST/VTTBuilder.h"
18 using namespace clang;
19 using namespace CodeGen;
21 static llvm::GlobalVariable *
22 GetAddrOfVTTVTable(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());
34 return CGVT.GenerateConstructionVTable(MostDerivedClass,
35 VTable.getBaseSubobject(),
42 CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
43 llvm::GlobalVariable::LinkageTypes Linkage,
44 const CXXRecordDecl *RD) {
45 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true);
47 llvm::Type *Int8PtrTy = CGM.Int8PtrTy, *Int64Ty = CGM.Int64Ty;
48 llvm::ArrayType *ArrayType =
49 llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
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()));
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 uint64_t AddressPoint;
66 if (VTTVT.getBase() == RD) {
67 // Just get the address point for the regular vtable.
69 getItaniumVTableContext().getVTableLayout(RD).getAddressPoint(
71 assert(AddressPoint != 0 && "Did not find vtable address point!");
73 AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
74 assert(AddressPoint != 0 && "Did not find ctor vtable address point!");
77 llvm::Value *Idxs[] = {
78 llvm::ConstantInt::get(Int64Ty, 0),
79 llvm::ConstantInt::get(Int64Ty, AddressPoint)
82 llvm::Constant *Init = llvm::ConstantExpr::getInBoundsGetElementPtr(
83 VTable->getValueType(), VTable, Idxs);
85 Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
87 VTTComponents.push_back(Init);
90 llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
92 VTT->setInitializer(Init);
94 // Set the correct linkage.
95 VTT->setLinkage(Linkage);
97 if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
98 VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
100 // Set the right visibility.
101 CGM.setGlobalVisibility(VTT, RD);
104 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
105 assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
107 SmallString<256> OutName;
108 llvm::raw_svector_ostream Out(OutName);
109 cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
110 .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());
122 llvm::GlobalVariable *GV =
123 CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType,
124 llvm::GlobalValue::ExternalLinkage);
125 GV->setUnnamedAddr(true);
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!");