Peter Collingbourne | 5c551f7 | 2011-09-26 01:56:24 +0000 | [diff] [blame] | 1 | //===--- VTTBuilder.cpp - C++ VTT layout builder --------------------------===// |
| 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 generation of the layout of virtual table |
| 11 | // tables (VTT). |
| 12 | // |
| 13 | //===----------------------------------------------------------------------===// |
| 14 | |
| 15 | #include "clang/AST/VTTBuilder.h" |
Benjamin Kramer | d4f5198 | 2012-07-04 18:45:14 +0000 | [diff] [blame] | 16 | #include "clang/AST/ASTContext.h" |
Peter Collingbourne | 5c551f7 | 2011-09-26 01:56:24 +0000 | [diff] [blame] | 17 | #include "clang/AST/CXXInheritance.h" |
| 18 | #include "clang/AST/RecordLayout.h" |
| 19 | #include "clang/Basic/TargetInfo.h" |
| 20 | #include "llvm/Support/Format.h" |
| 21 | #include <algorithm> |
| 22 | #include <cstdio> |
| 23 | |
| 24 | using namespace clang; |
| 25 | |
| 26 | #define DUMP_OVERRIDERS 0 |
| 27 | |
| 28 | VTTBuilder::VTTBuilder(ASTContext &Ctx, |
| 29 | const CXXRecordDecl *MostDerivedClass, |
| 30 | bool GenerateDefinition) |
| 31 | : Ctx(Ctx), MostDerivedClass(MostDerivedClass), |
| 32 | MostDerivedClassLayout(Ctx.getASTRecordLayout(MostDerivedClass)), |
| 33 | GenerateDefinition(GenerateDefinition) { |
| 34 | // Lay out this VTT. |
| 35 | LayoutVTT(BaseSubobject(MostDerivedClass, CharUnits::Zero()), |
| 36 | /*BaseIsVirtual=*/false); |
| 37 | } |
| 38 | |
| 39 | void VTTBuilder::AddVTablePointer(BaseSubobject Base, uint64_t VTableIndex, |
| 40 | const CXXRecordDecl *VTableClass) { |
| 41 | // Store the vtable pointer index if we're generating the primary VTT. |
| 42 | if (VTableClass == MostDerivedClass) { |
| 43 | assert(!SecondaryVirtualPointerIndices.count(Base) && |
| 44 | "A virtual pointer index already exists for this base subobject!"); |
| 45 | SecondaryVirtualPointerIndices[Base] = VTTComponents.size(); |
| 46 | } |
| 47 | |
| 48 | if (!GenerateDefinition) { |
| 49 | VTTComponents.push_back(VTTComponent()); |
| 50 | return; |
| 51 | } |
| 52 | |
| 53 | VTTComponents.push_back(VTTComponent(VTableIndex, Base)); |
| 54 | } |
| 55 | |
| 56 | void VTTBuilder::LayoutSecondaryVTTs(BaseSubobject Base) { |
| 57 | const CXXRecordDecl *RD = Base.getBase(); |
| 58 | |
| 59 | for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), |
| 60 | E = RD->bases_end(); I != E; ++I) { |
| 61 | |
| 62 | // Don't layout virtual bases. |
| 63 | if (I->isVirtual()) |
| 64 | continue; |
| 65 | |
| 66 | const CXXRecordDecl *BaseDecl = |
| 67 | cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); |
| 68 | |
| 69 | const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD); |
| 70 | CharUnits BaseOffset = Base.getBaseOffset() + |
| 71 | Layout.getBaseClassOffset(BaseDecl); |
| 72 | |
| 73 | // Layout the VTT for this base. |
| 74 | LayoutVTT(BaseSubobject(BaseDecl, BaseOffset), /*BaseIsVirtual=*/false); |
| 75 | } |
| 76 | } |
| 77 | |
| 78 | void |
| 79 | VTTBuilder::LayoutSecondaryVirtualPointers(BaseSubobject Base, |
| 80 | bool BaseIsMorallyVirtual, |
| 81 | uint64_t VTableIndex, |
| 82 | const CXXRecordDecl *VTableClass, |
| 83 | VisitedVirtualBasesSetTy &VBases) { |
| 84 | const CXXRecordDecl *RD = Base.getBase(); |
| 85 | |
| 86 | // We're not interested in bases that don't have virtual bases, and not |
| 87 | // morally virtual bases. |
| 88 | if (!RD->getNumVBases() && !BaseIsMorallyVirtual) |
| 89 | return; |
| 90 | |
| 91 | for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), |
| 92 | E = RD->bases_end(); I != E; ++I) { |
| 93 | const CXXRecordDecl *BaseDecl = |
| 94 | cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); |
| 95 | |
| 96 | // Itanium C++ ABI 2.6.2: |
| 97 | // Secondary virtual pointers are present for all bases with either |
| 98 | // virtual bases or virtual function declarations overridden along a |
| 99 | // virtual path. |
| 100 | // |
| 101 | // If the base class is not dynamic, we don't want to add it, nor any |
| 102 | // of its base classes. |
| 103 | if (!BaseDecl->isDynamicClass()) |
| 104 | continue; |
| 105 | |
| 106 | bool BaseDeclIsMorallyVirtual = BaseIsMorallyVirtual; |
| 107 | bool BaseDeclIsNonVirtualPrimaryBase = false; |
| 108 | CharUnits BaseOffset; |
| 109 | if (I->isVirtual()) { |
| 110 | // Ignore virtual bases that we've already visited. |
| 111 | if (!VBases.insert(BaseDecl)) |
| 112 | continue; |
| 113 | |
| 114 | BaseOffset = MostDerivedClassLayout.getVBaseClassOffset(BaseDecl); |
| 115 | BaseDeclIsMorallyVirtual = true; |
| 116 | } else { |
| 117 | const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD); |
| 118 | |
| 119 | BaseOffset = Base.getBaseOffset() + |
| 120 | Layout.getBaseClassOffset(BaseDecl); |
| 121 | |
| 122 | if (!Layout.isPrimaryBaseVirtual() && |
| 123 | Layout.getPrimaryBase() == BaseDecl) |
| 124 | BaseDeclIsNonVirtualPrimaryBase = true; |
| 125 | } |
| 126 | |
| 127 | // Itanium C++ ABI 2.6.2: |
| 128 | // Secondary virtual pointers: for each base class X which (a) has virtual |
| 129 | // bases or is reachable along a virtual path from D, and (b) is not a |
| 130 | // non-virtual primary base, the address of the virtual table for X-in-D |
| 131 | // or an appropriate construction virtual table. |
| 132 | if (!BaseDeclIsNonVirtualPrimaryBase && |
| 133 | (BaseDecl->getNumVBases() || BaseDeclIsMorallyVirtual)) { |
| 134 | // Add the vtable pointer. |
| 135 | AddVTablePointer(BaseSubobject(BaseDecl, BaseOffset), VTableIndex, |
| 136 | VTableClass); |
| 137 | } |
| 138 | |
| 139 | // And lay out the secondary virtual pointers for the base class. |
| 140 | LayoutSecondaryVirtualPointers(BaseSubobject(BaseDecl, BaseOffset), |
| 141 | BaseDeclIsMorallyVirtual, VTableIndex, |
| 142 | VTableClass, VBases); |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | void |
| 147 | VTTBuilder::LayoutSecondaryVirtualPointers(BaseSubobject Base, |
| 148 | uint64_t VTableIndex) { |
| 149 | VisitedVirtualBasesSetTy VBases; |
| 150 | LayoutSecondaryVirtualPointers(Base, /*BaseIsMorallyVirtual=*/false, |
| 151 | VTableIndex, Base.getBase(), VBases); |
| 152 | } |
| 153 | |
| 154 | void VTTBuilder::LayoutVirtualVTTs(const CXXRecordDecl *RD, |
| 155 | VisitedVirtualBasesSetTy &VBases) { |
| 156 | for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), |
| 157 | E = RD->bases_end(); I != E; ++I) { |
| 158 | const CXXRecordDecl *BaseDecl = |
| 159 | cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); |
| 160 | |
| 161 | // Check if this is a virtual base. |
| 162 | if (I->isVirtual()) { |
| 163 | // Check if we've seen this base before. |
| 164 | if (!VBases.insert(BaseDecl)) |
| 165 | continue; |
| 166 | |
| 167 | CharUnits BaseOffset = |
| 168 | MostDerivedClassLayout.getVBaseClassOffset(BaseDecl); |
| 169 | |
| 170 | LayoutVTT(BaseSubobject(BaseDecl, BaseOffset), /*BaseIsVirtual=*/true); |
| 171 | } |
| 172 | |
| 173 | // We only need to layout virtual VTTs for this base if it actually has |
| 174 | // virtual bases. |
| 175 | if (BaseDecl->getNumVBases()) |
| 176 | LayoutVirtualVTTs(BaseDecl, VBases); |
| 177 | } |
| 178 | } |
| 179 | |
| 180 | void VTTBuilder::LayoutVTT(BaseSubobject Base, bool BaseIsVirtual) { |
| 181 | const CXXRecordDecl *RD = Base.getBase(); |
| 182 | |
| 183 | // Itanium C++ ABI 2.6.2: |
| 184 | // An array of virtual table addresses, called the VTT, is declared for |
| 185 | // each class type that has indirect or direct virtual base classes. |
| 186 | if (RD->getNumVBases() == 0) |
| 187 | return; |
| 188 | |
| 189 | bool IsPrimaryVTT = Base.getBase() == MostDerivedClass; |
| 190 | |
| 191 | if (!IsPrimaryVTT) { |
| 192 | // Remember the sub-VTT index. |
| 193 | SubVTTIndicies[Base] = VTTComponents.size(); |
| 194 | } |
| 195 | |
| 196 | uint64_t VTableIndex = VTTVTables.size(); |
| 197 | VTTVTables.push_back(VTTVTable(Base, BaseIsVirtual)); |
| 198 | |
| 199 | // Add the primary vtable pointer. |
| 200 | AddVTablePointer(Base, VTableIndex, RD); |
| 201 | |
| 202 | // Add the secondary VTTs. |
| 203 | LayoutSecondaryVTTs(Base); |
| 204 | |
| 205 | // Add the secondary virtual pointers. |
| 206 | LayoutSecondaryVirtualPointers(Base, VTableIndex); |
| 207 | |
| 208 | // If this is the primary VTT, we want to lay out virtual VTTs as well. |
| 209 | if (IsPrimaryVTT) { |
| 210 | VisitedVirtualBasesSetTy VBases; |
| 211 | LayoutVirtualVTTs(Base.getBase(), VBases); |
| 212 | } |
| 213 | } |