contrib/llvm/tools/clang/lib/CodeGen/CGVTT.cpp

   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"
  18 using namespace clang;
  19 using namespace CodeGen;
  20
  21 #define D1(x)
  22
  23 llvm::Constant *GetAddrOfVTTVTable(CodeGenVTables &CGVT,
  24                                    const CXXRecordDecl *MostDerivedClass,
  25                                    const VTTVTable &VTable,
  26                                    llvm::GlobalVariable::LinkageTypes Linkage,
  27                        llvm::DenseMap<BaseSubobject, uint64_t> &AddressPoints) {
  28   if (VTable.getBase() == MostDerivedClass) {
  29     assert(VTable.getBaseOffset().isZero() &&
  30            "Most derived class vtable must have a zero offset!");
  31     // This is a regular vtable.
  32     return CGVT.GetAddrOfVTable(MostDerivedClass);
  33   }
  34
  35   return CGVT.GenerateConstructionVTable(MostDerivedClass,
  36                                          VTable.getBaseSubobject(),
  37                                          VTable.isVirtual(),
  38                                          Linkage,
  39                                          AddressPoints);
  40 }
  41
  42 void
  43 CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
  44                                   llvm::GlobalVariable::LinkageTypes Linkage,
  45                                   const CXXRecordDecl *RD) {
  46   VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true);
  47
  48   llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGM.getLLVMContext()),
  49              *Int64Ty = llvm::Type::getInt64Ty(CGM.getLLVMContext());
  50   llvm::ArrayType *ArrayType =
  51     llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
  52
  53   SmallVector<llvm::Constant *, 8> VTables;
  54   SmallVector<VTableAddressPointsMapTy, 8> VTableAddressPoints;
  55   for (const VTTVTable *i = Builder.getVTTVTables().begin(),
  56                        *e = Builder.getVTTVTables().end(); i != e; ++i) {
  57     VTableAddressPoints.push_back(VTableAddressPointsMapTy());
  58     VTables.push_back(GetAddrOfVTTVTable(*this, RD, *i, Linkage,
  59                                          VTableAddressPoints.back()));
  60   }
  61
  62   SmallVector<llvm::Constant *, 8> VTTComponents;
  63   for (const VTTComponent *i = Builder.getVTTComponents().begin(),
  64                           *e = Builder.getVTTComponents().end(); i != e; ++i) {
  65     const VTTVTable &VTTVT = Builder.getVTTVTables()[i->VTableIndex];
  66     llvm::Constant *VTable = VTables[i->VTableIndex];
  67     uint64_t AddressPoint;
  68     if (VTTVT.getBase() == RD) {
  69       // Just get the address point for the regular vtable.
  70       AddressPoint = VTContext.getVTableLayout(RD)
  71                               .getAddressPoint(i->VTableBase);
  72       assert(AddressPoint != 0 && "Did not find vtable address point!");
  73     } else {
  74       AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
  75       assert(AddressPoint != 0 && "Did not find ctor vtable address point!");
  76     }
  77
  78      llvm::Value *Idxs[] = {
  79        llvm::ConstantInt::get(Int64Ty, 0),
  80        llvm::ConstantInt::get(Int64Ty, AddressPoint)
  81      };
  82
  83      llvm::Constant *Init =
  84        llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Idxs);
  85
  86      Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
  87
  88      VTTComponents.push_back(Init);
  89   }
  90
  91   llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
  92
  93   VTT->setInitializer(Init);
  94
  95   // Set the correct linkage.
  96   VTT->setLinkage(Linkage);
  97
  98   // Set the right visibility.
  99   CGM.setTypeVisibility(VTT, RD, CodeGenModule::TVK_ForVTT);
 100 }
 101
 102 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
 103   assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
 104
 105   llvm::SmallString<256> OutName;
 106   llvm::raw_svector_ostream Out(OutName);
 107   CGM.getCXXABI().getMangleContext().mangleCXXVTT(RD, Out);
 108   Out.flush();
 109   StringRef Name = OutName.str();
 110
 111   // This will also defer the definition of the VTT.
 112   (void) GetAddrOfVTable(RD);
 113
 114   VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
 115
 116   llvm::Type *Int8PtrTy =
 117     llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
 118   llvm::ArrayType *ArrayType =
 119     llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
 120
 121   llvm::GlobalVariable *GV =
 122     CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType,
 123                                           llvm::GlobalValue::ExternalLinkage);
 124   GV->setUnnamedAddr(true);
 125   return GV;
 126 }
 127
 128 bool CodeGenVTables::needsVTTParameter(GlobalDecl GD) {
 129   const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
 130
 131   // We don't have any virtual bases, just return early.
 132   if (!MD->getParent()->getNumVBases())
 133     return false;
 134
 135   // Check if we have a base constructor.
 136   if (isa<CXXConstructorDecl>(MD) && GD.getCtorType() == Ctor_Base)
 137     return true;
 138
 139   // Check if we have a base destructor.
 140   if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
 141     return true;
 142
 143   return false;
 144 }
 145
 146 uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,
 147                                         BaseSubobject Base) {
 148   BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
 149
 150   SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
 151   if (I != SubVTTIndicies.end())
 152     return I->second;
 153
 154   VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
 155
 156   for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
 157        Builder.getSubVTTIndicies().begin(),
 158        E = Builder.getSubVTTIndicies().end(); I != E; ++I) {
 159     // Insert all indices.
 160     BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);
 161
 162     SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
 163   }
 164
 165   I = SubVTTIndicies.find(ClassSubobjectPair);
 166   assert(I != SubVTTIndicies.end() && "Did not find index!");
 167
 168   return I->second;
 169 }
 170
 171 uint64_t
 172 CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
 173                                                 BaseSubobject Base) {
 174   SecondaryVirtualPointerIndicesMapTy::iterator I =
 175     SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
 176
 177   if (I != SecondaryVirtualPointerIndices.end())
 178     return I->second;
 179
 180   VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
 181
 182   // Insert all secondary vpointer indices.
 183   for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
 184        Builder.getSecondaryVirtualPointerIndices().begin(),
 185        E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {
 186     std::pair<const CXXRecordDecl *, BaseSubobject> Pair =
 187       std::make_pair(RD, I->first);
 188
 189     SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
 190   }
 191
 192   I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
 193   assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");
 194
 195   return I->second;
 196 }
 197