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 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());
  32   }
  33
  34   return CGVT.GenerateConstructionVTable(MostDerivedClass,
  35                                          VTable.getBaseSubobject(),
  36                                          VTable.isVirtual(),
  37                                          Linkage,
  38                                          AddressPoints);
  39 }
  40
  41 void
  42 CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
  43                                   llvm::GlobalVariable::LinkageTypes Linkage,
  44                                   const CXXRecordDecl *RD) {
  45   VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true);
  46
  47   llvm::Type *Int8PtrTy = CGM.Int8PtrTy, *Int64Ty = CGM.Int64Ty;
  48   llvm::ArrayType *ArrayType =
  49     llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
  50
  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()));
  58   }
  59
  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.
  68       AddressPoint =
  69           ItaniumVTContext.getVTableLayout(RD).getAddressPoint(i->VTableBase);
  70       assert(AddressPoint != 0 && "Did not find vtable address point!");
  71     } else {
  72       AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
  73       assert(AddressPoint != 0 && "Did not find ctor vtable address point!");
  74     }
  75
  76      llvm::Value *Idxs[] = {
  77        llvm::ConstantInt::get(Int64Ty, 0),
  78        llvm::ConstantInt::get(Int64Ty, AddressPoint)
  79      };
  80
  81      llvm::Constant *Init =
  82        llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Idxs);
  83
  84      Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
  85
  86      VTTComponents.push_back(Init);
  87   }
  88
  89   llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
  90
  91   VTT->setInitializer(Init);
  92
  93   // Set the correct linkage.
  94   VTT->setLinkage(Linkage);
  95
  96   // Set the right visibility.
  97   CGM.setTypeVisibility(VTT, RD, CodeGenModule::TVK_ForVTT);
  98 }
  99
 100 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
 101   assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
 102
 103   SmallString<256> OutName;
 104   llvm::raw_svector_ostream Out(OutName);
 105   cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
 106       .mangleCXXVTT(RD, Out);
 107   Out.flush();
 108   StringRef Name = OutName.str();
 109
 110   // This will also defer the definition of the VTT.
 111   (void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());
 112
 113   VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
 114
 115   llvm::ArrayType *ArrayType =
 116     llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
 117
 118   llvm::GlobalVariable *GV =
 119     CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType,
 120                                           llvm::GlobalValue::ExternalLinkage);
 121   GV->setUnnamedAddr(true);
 122   return GV;
 123 }
 124
 125 uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,
 126                                         BaseSubobject Base) {
 127   BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
 128
 129   SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
 130   if (I != SubVTTIndicies.end())
 131     return I->second;
 132
 133   VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
 134
 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);
 140
 141     SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
 142   }
 143
 144   I = SubVTTIndicies.find(ClassSubobjectPair);
 145   assert(I != SubVTTIndicies.end() && "Did not find index!");
 146
 147   return I->second;
 148 }
 149
 150 uint64_t
 151 CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
 152                                                 BaseSubobject Base) {
 153   SecondaryVirtualPointerIndicesMapTy::iterator I =
 154     SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
 155
 156   if (I != SecondaryVirtualPointerIndices.end())
 157     return I->second;
 158
 159   VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
 160
 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);
 167
 168     SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
 169   }
 170
 171   I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
 172   assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");
 173
 174   return I->second;
 175 }
 176