clang  16.0.0git
CGVTT.cpp
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1 //===--- CGVTT.cpp - Emit LLVM Code for C++ VTTs --------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This contains code dealing with C++ code generation of VTTs (vtable tables).
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "CodeGenModule.h"
14 #include "CGCXXABI.h"
15 #include "clang/AST/RecordLayout.h"
16 #include "clang/AST/VTTBuilder.h"
17 using namespace clang;
18 using namespace CodeGen;
19 
20 static llvm::GlobalVariable *
22  const CXXRecordDecl *MostDerivedClass,
23  const VTTVTable &VTable,
24  llvm::GlobalVariable::LinkageTypes Linkage,
25  VTableLayout::AddressPointsMapTy &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 CGM.getCXXABI().getAddrOfVTable(MostDerivedClass, CharUnits());
31  }
32 
33  return CGVT.GenerateConstructionVTable(MostDerivedClass,
34  VTable.getBaseSubobject(),
35  VTable.isVirtual(),
36  Linkage,
37  AddressPoints);
38 }
39 
40 void
41 CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
42  llvm::GlobalVariable::LinkageTypes Linkage,
43  const CXXRecordDecl *RD) {
44  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true);
45  llvm::ArrayType *ArrayType =
46  llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
47 
49  SmallVector<VTableAddressPointsMapTy, 8> VTableAddressPoints;
50  for (const VTTVTable *i = Builder.getVTTVTables().begin(),
51  *e = Builder.getVTTVTables().end(); i != e; ++i) {
52  VTableAddressPoints.push_back(VTableAddressPointsMapTy());
53  VTables.push_back(GetAddrOfVTTVTable(*this, CGM, RD, *i, Linkage,
54  VTableAddressPoints.back()));
55  }
56 
58  for (const VTTComponent *i = Builder.getVTTComponents().begin(),
59  *e = Builder.getVTTComponents().end(); i != e; ++i) {
60  const VTTVTable &VTTVT = Builder.getVTTVTables()[i->VTableIndex];
61  llvm::GlobalVariable *VTable = VTables[i->VTableIndex];
63  if (VTTVT.getBase() == RD) {
64  // Just get the address point for the regular vtable.
65  AddressPoint =
67  i->VTableBase);
68  } else {
69  AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
70  assert(AddressPoint.AddressPointIndex != 0 &&
71  "Did not find ctor vtable address point!");
72  }
73 
74  llvm::Value *Idxs[] = {
75  llvm::ConstantInt::get(CGM.Int32Ty, 0),
76  llvm::ConstantInt::get(CGM.Int32Ty, AddressPoint.VTableIndex),
77  llvm::ConstantInt::get(CGM.Int32Ty, AddressPoint.AddressPointIndex),
78  };
79 
80  llvm::Constant *Init = llvm::ConstantExpr::getGetElementPtr(
81  VTable->getValueType(), VTable, Idxs, /*InBounds=*/true,
82  /*InRangeIndex=*/1);
83 
84  Init = llvm::ConstantExpr::getPointerBitCastOrAddrSpaceCast(Init,
85  CGM.Int8PtrTy);
86 
87  VTTComponents.push_back(Init);
88  }
89 
90  llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
91 
92  VTT->setInitializer(Init);
93 
94  // Set the correct linkage.
95  VTT->setLinkage(Linkage);
96 
97  if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
98  VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
99 }
100 
101 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
102  assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
103 
104  SmallString<256> OutName;
105  llvm::raw_svector_ostream Out(OutName);
106  cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
107  .mangleCXXVTT(RD, Out);
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  unsigned Align = CGM.getDataLayout().getABITypeAlignment(CGM.Int8PtrTy);
118 
119  llvm::GlobalVariable *GV = CGM.CreateOrReplaceCXXRuntimeVariable(
121  GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
122  CGM.setGVProperties(GV, RD);
123  return GV;
124 }
125 
128  BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
129 
130  SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
131  if (I != SubVTTIndicies.end())
132  return I->second;
133 
134  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
135 
136  for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
137  Builder.getSubVTTIndicies().begin(),
138  E = Builder.getSubVTTIndicies().end(); I != E; ++I) {
139  // Insert all indices.
140  BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);
141 
142  SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
143  }
144 
145  I = SubVTTIndicies.find(ClassSubobjectPair);
146  assert(I != SubVTTIndicies.end() && "Did not find index!");
147 
148  return I->second;
149 }
150 
151 uint64_t
154  SecondaryVirtualPointerIndicesMapTy::iterator I =
155  SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
156 
157  if (I != SecondaryVirtualPointerIndices.end())
158  return I->second;
159 
160  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
161 
162  // Insert all secondary vpointer indices.
163  for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
164  Builder.getSecondaryVirtualPointerIndices().begin(),
165  E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {
166  std::pair<const CXXRecordDecl *, BaseSubobject> Pair =
167  std::make_pair(RD, I->first);
168 
169  SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
170  }
171 
172  I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
173  assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");
174 
175  return I->second;
176 }
clang::CodeGen::CodeGenTypeCache::Int8PtrTy
llvm::PointerType * Int8PtrTy
Definition: CodeGenTypeCache.h:57
VTTBuilder.h
llvm::SmallVector
Definition: LLVM.h:38
clang::VTTVTable::getBaseSubobject
BaseSubobject getBaseSubobject() const
Definition: VTTBuilder.h:56
clang::CodeGen::CGCXXABI::getMangleContext
MangleContext & getMangleContext()
Gets the mangle context.
Definition: CGCXXABI.h:117
clang::CodeGen::CodeGenVTables::GenerateConstructionVTable
llvm::GlobalVariable * GenerateConstructionVTable(const CXXRecordDecl *RD, const BaseSubobject &Base, bool BaseIsVirtual, llvm::GlobalVariable::LinkageTypes Linkage, VTableAddressPointsMapTy &AddressPoints)
GenerateConstructionVTable - Generate a construction vtable for the given base subobject.
Definition: CGVTables.cpp:864
clang::CodeGen::CodeGenModule::getContext
ASTContext & getContext() const
Definition: CodeGenModule.h:722
clang::CodeGen::CodeGenVTables::GetAddrOfVTT
llvm::GlobalVariable * GetAddrOfVTT(const CXXRecordDecl *RD)
GetAddrOfVTT - Get the address of the VTT for the given record decl.
Definition: CGVTT.cpp:101
GetAddrOfVTTVTable
static llvm::GlobalVariable * GetAddrOfVTTVTable(CodeGenVTables &CGVT, CodeGenModule &CGM, const CXXRecordDecl *MostDerivedClass, const VTTVTable &VTable, llvm::GlobalVariable::LinkageTypes Linkage, VTableLayout::AddressPointsMapTy &AddressPoints)
Definition: CGVTT.cpp:21
clang::VTTBuilder
Class for building VTT layout information.
Definition: VTTBuilder.h:71
clang::VTTVTable::getBase
const CXXRecordDecl * getBase() const
Definition: VTTBuilder.h:44
clang::CodeGen::CGCXXABI::getAddrOfVTable
virtual llvm::GlobalVariable * getAddrOfVTable(const CXXRecordDecl *RD, CharUnits VPtrOffset)=0
Get the address of the vtable for the given record decl which should be used for the vptr at the give...
clang::VTTComponent
Definition: VTTBuilder.h:61
clang::VTableLayout::AddressPointLocation
Definition: VTableBuilder.h:236
clang::Linkage
Linkage
Describes the different kinds of linkage (C++ [basic.link], C99 6.2.2) that an entity may have.
Definition: Linkage.h:23
clang::CodeGen::CodeGenVTables::getSecondaryVirtualPointerIndex
uint64_t getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD, BaseSubobject Base)
getSecondaryVirtualPointerIndex - Return the index in the VTT where the virtual pointer for the given...
Definition: CGVTT.cpp:152
hlsl::uint64_t
unsigned long uint64_t
Definition: hlsl_basic_types.h:25
clang::BaseSubobject
Definition: BaseSubobject.h:30
clang::ArrayType
Represents an array type, per C99 6.7.5.2 - Array Declarators.
Definition: Type.h:3012
clang::VTTVTable::getBaseOffset
CharUnits getBaseOffset() const
Definition: VTTBuilder.h:48
clang::CodeGen::CodeGenModule::getModule
llvm::Module & getModule() const
Definition: CodeGenModule.h:732
llvm::SmallString
Definition: LLVM.h:37
Base
CodeGenModule.h
clang::VTableLayout::AddressPointLocation::VTableIndex
unsigned VTableIndex
Definition: VTableBuilder.h:237
clang::VTableLayout::AddressPointLocation::AddressPointIndex
unsigned AddressPointIndex
Definition: VTableBuilder.h:237
clang::CodeGen::CodeGenTypeCache::Int32Ty
llvm::IntegerType * Int32Ty
Definition: CodeGenTypeCache.h:37
clang::VTableLayout::AddressPointsMapTy
llvm::DenseMap< BaseSubobject, AddressPointLocation > AddressPointsMapTy
Definition: VTableBuilder.h:240
clang::CodeGen::CodeGenVTables::EmitVTTDefinition
void EmitVTTDefinition(llvm::GlobalVariable *VTT, llvm::GlobalVariable::LinkageTypes Linkage, const CXXRecordDecl *RD)
EmitVTTDefinition - Emit the definition of the given vtable.
Definition: CGVTT.cpp:41
clang::CodeGen::CodeGenModule::getDataLayout
const llvm::DataLayout & getDataLayout() const
Definition: CodeGenModule.h:734
clang::CXXRecordDecl
Represents a C++ struct/union/class.
Definition: DeclCXX.h:254
clang::VTTVTable::isVirtual
bool isVirtual() const
Definition: VTTBuilder.h:52
clang::CXXRecordDecl::getNumVBases
unsigned getNumVBases() const
Retrieves the number of virtual base classes of this class.
Definition: DeclCXX.h:612
clang::VTableLayout::getAddressPoint
AddressPointLocation getAddressPoint(BaseSubobject Base) const
Definition: VTableBuilder.h:280
clang::CharUnits::isZero
bool isZero() const
isZero - Test whether the quantity equals zero.
Definition: CharUnits.h:116
clang::CodeGen::CodeGenModule::getCXXABI
CGCXXABI & getCXXABI() const
Definition: CodeGenModule.h:742
clang::CodeGen::CodeGenModule
This class organizes the cross-function state that is used while generating LLVM code.
Definition: CodeGenModule.h:279
clang::CodeGen::CodeGenVTables::getSubVTTIndex
uint64_t getSubVTTIndex(const CXXRecordDecl *RD, BaseSubobject Base)
getSubVTTIndex - Return the index of the sub-VTT for the base class of the given record decl.
Definition: CGVTT.cpp:126
clang::CodeGen::CodeGenModule::supportsCOMDAT
bool supportsCOMDAT() const
Definition: TargetInfo.cpp:12063
CGCXXABI.h
clang::VTTVTable
Definition: VTTBuilder.h:32
clang
Definition: CalledOnceCheck.h:17
clang::ExternalLinkage
@ ExternalLinkage
External linkage, which indicates that the entity can be referred to from other translation units.
Definition: Linkage.h:59
clang::ItaniumVTableContext::getVTableLayout
const VTableLayout & getVTableLayout(const CXXRecordDecl *RD)
Definition: VTableBuilder.h:403
clang::CodeGen::CodeGenVTables
Definition: CGVTables.h:32
clang::CharUnits
CharUnits - This is an opaque type for sizes expressed in character units.
Definition: CharUnits.h:38
clang::CodeGen::CodeGenVTables::getItaniumVTableContext
ItaniumVTableContext & getItaniumVTableContext()
Definition: CGVTables.h:101
clang::CodeGen::CodeGenModule::CreateOrReplaceCXXRuntimeVariable
llvm::GlobalVariable * CreateOrReplaceCXXRuntimeVariable(StringRef Name, llvm::Type *Ty, llvm::GlobalValue::LinkageTypes Linkage, unsigned Alignment)
Will return a global variable of the given type.
Definition: CodeGenModule.cpp:4496
clang::CodeGen::CodeGenModule::setGVProperties
void setGVProperties(llvm::GlobalValue *GV, GlobalDecl GD) const
Set visibility, dllimport/dllexport and dso_local.
Definition: CodeGenModule.cpp:1255
RecordLayout.h