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::Constant *
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::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()));
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.
69 ItaniumVTContext.getVTableLayout(RD).getAddressPoint(i->VTableBase);
70 assert(AddressPoint != 0 && "Did not find vtable address point!");
72 AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
73 assert(AddressPoint != 0 && "Did not find ctor vtable address point!");
76 llvm::Value *Idxs[] = {
77 llvm::ConstantInt::get(Int64Ty, 0),
78 llvm::ConstantInt::get(Int64Ty, AddressPoint)
81 llvm::Constant *Init =
82 llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Idxs);
84 Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
86 VTTComponents.push_back(Init);
89 llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
91 VTT->setInitializer(Init);
93 // Set the correct linkage.
94 VTT->setLinkage(Linkage);
96 // Set the right visibility.
97 CGM.setTypeVisibility(VTT, RD, CodeGenModule::TVK_ForVTT);
100 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
101 assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
103 SmallString<256> OutName;
104 llvm::raw_svector_ostream Out(OutName);
105 cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
106 .mangleCXXVTT(RD, Out);
108 StringRef Name = OutName.str();
110 // This will also defer the definition of the VTT.
111 (void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());
113 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
115 llvm::ArrayType *ArrayType =
116 llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
118 llvm::GlobalVariable *GV =
119 CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType,
120 llvm::GlobalValue::ExternalLinkage);
121 GV->setUnnamedAddr(true);
125 uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,
126 BaseSubobject Base) {
127 BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
129 SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
130 if (I != SubVTTIndicies.end())
133 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
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);
141 SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
144 I = SubVTTIndicies.find(ClassSubobjectPair);
145 assert(I != SubVTTIndicies.end() && "Did not find index!");
151 CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
152 BaseSubobject Base) {
153 SecondaryVirtualPointerIndicesMapTy::iterator I =
154 SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
156 if (I != SecondaryVirtualPointerIndices.end())
159 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
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);
168 SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
171 I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
172 assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");