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, const CXXRecordDecl *MostDerivedClass,
23                   const VTTVTable &VTable,
24                   llvm::GlobalVariable::LinkageTypes Linkage,
25                   llvm::DenseMap<BaseSubobject, uint64_t> &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 CGVT.GetAddrOfVTable(MostDerivedClass);
31  }
32
33  return CGVT.GenerateConstructionVTable(MostDerivedClass,
34                                         VTable.getBaseSubobject(),
35                                         VTable.isVirtual(),
36                                         Linkage,
37                                         AddressPoints);
38}
39
40void
41CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
42                                  llvm::GlobalVariable::LinkageTypes Linkage,
43                                  const CXXRecordDecl *RD) {
44  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true);
45
46  llvm::Type *Int8PtrTy = CGM.Int8PtrTy, *Int64Ty = CGM.Int64Ty;
47  llvm::ArrayType *ArrayType =
48    llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
49
50  SmallVector<llvm::Constant *, 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, RD, *i, Linkage,
56                                         VTableAddressPoints.back()));
57  }
58
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::Constant *VTable = VTables[i->VTableIndex];
64    uint64_t AddressPoint;
65    if (VTTVT.getBase() == RD) {
66      // Just get the address point for the regular vtable.
67      AddressPoint = VTContext.getVTableLayout(RD)
68                              .getAddressPoint(i->VTableBase);
69      assert(AddressPoint != 0 && "Did not find vtable address point!");
70    } else {
71      AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
72      assert(AddressPoint != 0 && "Did not find ctor vtable address point!");
73    }
74
75     llvm::Value *Idxs[] = {
76       llvm::ConstantInt::get(Int64Ty, 0),
77       llvm::ConstantInt::get(Int64Ty, AddressPoint)
78     };
79
80     llvm::Constant *Init =
81       llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Idxs);
82
83     Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
84
85     VTTComponents.push_back(Init);
86  }
87
88  llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
89
90  VTT->setInitializer(Init);
91
92  // Set the correct linkage.
93  VTT->setLinkage(Linkage);
94
95  // Set the right visibility.
96  CGM.setTypeVisibility(VTT, RD, CodeGenModule::TVK_ForVTT);
97}
98
99llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
100  assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
101
102  SmallString<256> OutName;
103  llvm::raw_svector_ostream Out(OutName);
104  CGM.getCXXABI().getMangleContext().mangleCXXVTT(RD, Out);
105  Out.flush();
106  StringRef Name = OutName.str();
107
108  // This will also defer the definition of the VTT.
109  (void) GetAddrOfVTable(RD);
110
111  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
112
113  llvm::ArrayType *ArrayType =
114    llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
115
116  llvm::GlobalVariable *GV =
117    CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType,
118                                          llvm::GlobalValue::ExternalLinkage);
119  GV->setUnnamedAddr(true);
120  return GV;
121}
122
123bool CodeGenVTables::needsVTTParameter(GlobalDecl GD) {
124  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
125
126  // We don't have any virtual bases, just return early.
127  if (!MD->getParent()->getNumVBases())
128    return false;
129
130  // Check if we have a base constructor.
131  if (isa<CXXConstructorDecl>(MD) && GD.getCtorType() == Ctor_Base)
132    return true;
133
134  // Check if we have a base destructor.
135  if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
136    return true;
137
138  return false;
139}
140
141uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,
142                                        BaseSubobject Base) {
143  BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
144
145  SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
146  if (I != SubVTTIndicies.end())
147    return I->second;
148
149  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
150
151  for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
152       Builder.getSubVTTIndicies().begin(),
153       E = Builder.getSubVTTIndicies().end(); I != E; ++I) {
154    // Insert all indices.
155    BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);
156
157    SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
158  }
159
160  I = SubVTTIndicies.find(ClassSubobjectPair);
161  assert(I != SubVTTIndicies.end() && "Did not find index!");
162
163  return I->second;
164}
165
166uint64_t
167CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
168                                                BaseSubobject Base) {
169  SecondaryVirtualPointerIndicesMapTy::iterator I =
170    SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
171
172  if (I != SecondaryVirtualPointerIndices.end())
173    return I->second;
174
175  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
176
177  // Insert all secondary vpointer indices.
178  for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
179       Builder.getSecondaryVirtualPointerIndices().begin(),
180       E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {
181    std::pair<const CXXRecordDecl *, BaseSubobject> Pair =
182      std::make_pair(RD, I->first);
183
184    SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
185  }
186
187  I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
188  assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");
189
190  return I->second;
191}
192
193