clang 19.0.0git
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"
17using namespace clang;
18using namespace CodeGen;
19
20static 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
40void
41CodeGenVTables::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 = llvm::ArrayType::get(
46 CGM.GlobalsInt8PtrTy, Builder.getVTTComponents().size());
47
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 // Add inrange attribute to indicate that only the VTableIndex can be
81 // accessed.
82 unsigned ComponentSize =
83 CGM.getDataLayout().getTypeAllocSize(getVTableComponentType());
84 unsigned VTableSize = CGM.getDataLayout().getTypeAllocSize(
85 cast<llvm::StructType>(VTable->getValueType())
86 ->getElementType(AddressPoint.VTableIndex));
87 unsigned Offset = ComponentSize * AddressPoint.AddressPointIndex;
88 llvm::ConstantRange InRange(llvm::APInt(32, -Offset, true),
89 llvm::APInt(32, VTableSize - Offset, true));
90 llvm::Constant *Init = llvm::ConstantExpr::getGetElementPtr(
91 VTable->getValueType(), VTable, Idxs, /*InBounds=*/true, InRange);
92
93 VTTComponents.push_back(Init);
94 }
95
96 llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
97
98 VTT->setInitializer(Init);
99
100 // Set the correct linkage.
101 VTT->setLinkage(Linkage);
102
103 if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
104 VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
105
106 // Set the visibility. This will already have been set on the VTT declaration.
107 // Set it again, now that we have a definition, as the implicit visibility can
108 // apply differently to definitions.
109 CGM.setGVProperties(VTT, RD);
110}
111
112llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
113 assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
114
115 SmallString<256> OutName;
116 llvm::raw_svector_ostream Out(OutName);
117 cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
118 .mangleCXXVTT(RD, Out);
119 StringRef Name = OutName.str();
120
121 // This will also defer the definition of the VTT.
122 (void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());
123
124 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
125
126 llvm::ArrayType *ArrayType = llvm::ArrayType::get(
127 CGM.GlobalsInt8PtrTy, Builder.getVTTComponents().size());
128 llvm::Align Align = CGM.getDataLayout().getABITypeAlign(CGM.GlobalsInt8PtrTy);
129
130 llvm::GlobalVariable *GV = CGM.CreateOrReplaceCXXRuntimeVariable(
131 Name, ArrayType, llvm::GlobalValue::ExternalLinkage, Align);
132 GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
133 CGM.setGVProperties(GV, RD);
134 return GV;
135}
136
139 BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
140
141 SubVTTIndicesMapTy::iterator I = SubVTTIndices.find(ClassSubobjectPair);
142 if (I != SubVTTIndices.end())
143 return I->second;
144
145 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
146
147 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator
148 I = Builder.getSubVTTIndices().begin(),
149 E = Builder.getSubVTTIndices().end();
150 I != E; ++I) {
151 // Insert all indices.
152 BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);
153
154 SubVTTIndices.insert(std::make_pair(ClassSubobjectPair, I->second));
155 }
156
157 I = SubVTTIndices.find(ClassSubobjectPair);
158 assert(I != SubVTTIndices.end() && "Did not find index!");
159
160 return I->second;
161}
162
163uint64_t
166 SecondaryVirtualPointerIndicesMapTy::iterator I =
167 SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
168
169 if (I != SecondaryVirtualPointerIndices.end())
170 return I->second;
171
172 VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
173
174 // Insert all secondary vpointer indices.
175 for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
176 Builder.getSecondaryVirtualPointerIndices().begin(),
177 E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {
178 std::pair<const CXXRecordDecl *, BaseSubobject> Pair =
179 std::make_pair(RD, I->first);
180
181 SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
182 }
183
184 I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
185 assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");
186
187 return I->second;
188}
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
Represents an array type, per C99 6.7.5.2 - Array Declarators.
Definition: Type.h:3537
Represents a C++ struct/union/class.
Definition: DeclCXX.h:258
unsigned getNumVBases() const
Retrieves the number of virtual base classes of this class.
Definition: DeclCXX.h:634
CharUnits - This is an opaque type for sizes expressed in character units.
Definition: CharUnits.h:38
bool isZero() const
isZero - Test whether the quantity equals zero.
Definition: CharUnits.h:122
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...
MangleContext & getMangleContext()
Gets the mangle context.
Definition: CGCXXABI.h:113
This class organizes the cross-function state that is used while generating LLVM code.
void setGVProperties(llvm::GlobalValue *GV, GlobalDecl GD) const
Set visibility, dllimport/dllexport and dso_local.
llvm::Module & getModule() const
const llvm::DataLayout & getDataLayout() const
CGCXXABI & getCXXABI() const
ASTContext & getContext() const
llvm::GlobalVariable * CreateOrReplaceCXXRuntimeVariable(StringRef Name, llvm::Type *Ty, llvm::GlobalValue::LinkageTypes Linkage, llvm::Align Alignment)
Will return a global variable of the given type.
llvm::GlobalVariable * GetAddrOfVTT(const CXXRecordDecl *RD)
GetAddrOfVTT - Get the address of the VTT for the given record decl.
Definition: CGVTT.cpp:112
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:137
ItaniumVTableContext & getItaniumVTableContext()
Definition: CGVTables.h:91
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:891
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:164
void EmitVTTDefinition(llvm::GlobalVariable *VTT, llvm::GlobalVariable::LinkageTypes Linkage, const CXXRecordDecl *RD)
EmitVTTDefinition - Emit the definition of the given vtable.
Definition: CGVTT.cpp:41
const VTableLayout & getVTableLayout(const CXXRecordDecl *RD)
Class for building VTT layout information.
Definition: VTTBuilder.h:71
CharUnits getBaseOffset() const
Definition: VTTBuilder.h:48
bool isVirtual() const
Definition: VTTBuilder.h:52
const CXXRecordDecl * getBase() const
Definition: VTTBuilder.h:44
BaseSubobject getBaseSubobject() const
Definition: VTTBuilder.h:56
llvm::DenseMap< BaseSubobject, AddressPointLocation > AddressPointsMapTy
AddressPointLocation getAddressPoint(BaseSubobject Base) const
The JSON file list parser is used to communicate input to InstallAPI.
Linkage
Describes the different kinds of linkage (C++ [basic.link], C99 6.2.2) that an entity may have.
Definition: Linkage.h:24
llvm::PointerType * GlobalsInt8PtrTy