Clang Project

clang_source_code/lib/CodeGen/CGVTT.cpp
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"
17using namespace clang;
18using namespace CodeGen;
19
20static llvm::GlobalVariable *
21GetAddrOfVTTVTable(CodeGenVTables &CGVT, CodeGenModule &CGM,
22                   const CXXRecordDecl *MostDerivedClass,
23                   const VTTVTable &VTable,
24                   llvm::GlobalVariable::LinkageTypes Linkage,
25                   VTableLayout::AddressPointsMapTy &AddressPoints) {
26  if (VTable.getBase() == MostDerivedClass) {
27     (0) . __assert_fail ("VTable.getBaseOffset().isZero() && \"Most derived class vtable must have a zero offset!\"", "/home/seafit/code_projects/clang_source/clang/lib/CodeGen/CGVTT.cpp", 28, __PRETTY_FUNCTION__))" file_link="../../../include/assert.h.html#88" macro="true">assert(VTable.getBaseOffset().isZero() &&
28 (0) . __assert_fail ("VTable.getBaseOffset().isZero() && \"Most derived class vtable must have a zero offset!\"", "/home/seafit/code_projects/clang_source/clang/lib/CodeGen/CGVTT.cpp", 28, __PRETTY_FUNCTION__))" file_link="../../../include/assert.h.html#88" macro="true">           "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
46  llvm::Type *Int8PtrTy = CGM.Int8PtrTy, *Int32Ty = CGM.Int32Ty;
47  llvm::ArrayType *ArrayType =
48    llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
49
50  SmallVector<llvm::GlobalVariable *, 8> VTables;
51  SmallVector<VTableAddressPointsMapTy, 8> VTableAddressPoints;
52  for (const VTTVTable *i = Builder.getVTTVTables().begin(),
53                       *e = Builder.getVTTVTables().end(); i != e; ++i) {
54    VTableAddressPoints.push_back(VTableAddressPointsMapTy());
55    VTables.push_back(GetAddrOfVTTVTable(*this, CGM, RD, *i, Linkage,
56                                         VTableAddressPoints.back()));
57  }
58
59  SmallVector<llvm::Constant *, 8> VTTComponents;
60  for (const VTTComponent *i = Builder.getVTTComponents().begin(),
61                          *e = Builder.getVTTComponents().end(); i != e; ++i) {
62    const VTTVTable &VTTVT = Builder.getVTTVTables()[i->VTableIndex];
63    llvm::GlobalVariable *VTable = VTables[i->VTableIndex];
64    VTableLayout::AddressPointLocation AddressPoint;
65    if (VTTVT.getBase() == RD) {
66      // Just get the address point for the regular vtable.
67      AddressPoint =
68          getItaniumVTableContext().getVTableLayout(RD).getAddressPoint(
69              i->VTableBase);
70    } else {
71      AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
72       (0) . __assert_fail ("AddressPoint.AddressPointIndex != 0 && \"Did not find ctor vtable address point!\"", "/home/seafit/code_projects/clang_source/clang/lib/CodeGen/CGVTT.cpp", 73, __PRETTY_FUNCTION__))" file_link="../../../include/assert.h.html#88" macro="true">assert(AddressPoint.AddressPointIndex != 0 &&
73 (0) . __assert_fail ("AddressPoint.AddressPointIndex != 0 && \"Did not find ctor vtable address point!\"", "/home/seafit/code_projects/clang_source/clang/lib/CodeGen/CGVTT.cpp", 73, __PRETTY_FUNCTION__))" file_link="../../../include/assert.h.html#88" macro="true">             "Did not find ctor vtable address point!");
74    }
75
76     llvm::Value *Idxs[] = {
77       llvm::ConstantInt::get(Int32Ty, 0),
78       llvm::ConstantInt::get(Int32Ty, AddressPoint.VTableIndex),
79       llvm::ConstantInt::get(Int32Ty, AddressPoint.AddressPointIndex),
80     };
81
82     llvm::Constant *Init = llvm::ConstantExpr::getGetElementPtr(
83         VTable->getValueType(), VTable, Idxs, /*InBounds=*/true,
84         /*InRangeIndex=*/1);
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  if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
99    VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
100
101  // Set the right visibility.
102  CGM.setGVProperties(VTT, RD);
103}
104
105llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
106   (0) . __assert_fail ("RD->getNumVBases() && \"Only classes with virtual bases need a VTT\"", "/home/seafit/code_projects/clang_source/clang/lib/CodeGen/CGVTT.cpp", 106, __PRETTY_FUNCTION__))" file_link="../../../include/assert.h.html#88" macro="true">assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
107
108  SmallString<256> OutName;
109  llvm::raw_svector_ostream Out(OutName);
110  cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
111      .mangleCXXVTT(RD, Out);
112  StringRef Name = OutName.str();
113
114  // This will also defer the definition of the VTT.
115  (void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());
116
117  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
118
119  llvm::ArrayType *ArrayType =
120    llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
121  unsigned Align = CGM.getDataLayout().getABITypeAlignment(CGM.Int8PtrTy);
122
123  llvm::GlobalVariable *GV = CGM.CreateOrReplaceCXXRuntimeVariable(
124      Name, ArrayType, llvm::GlobalValue::ExternalLinkage, Align);
125  GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
126  return GV;
127}
128
129uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,
130                                        BaseSubobject Base) {
131  BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
132
133  SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
134  if (I != SubVTTIndicies.end())
135    return I->second;
136
137  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
138
139  for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
140       Builder.getSubVTTIndicies().begin(),
141       E = Builder.getSubVTTIndicies().end(); I != E; ++I) {
142    // Insert all indices.
143    BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);
144
145    SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
146  }
147
148  I = SubVTTIndicies.find(ClassSubobjectPair);
149   (0) . __assert_fail ("I != SubVTTIndicies.end() && \"Did not find index!\"", "/home/seafit/code_projects/clang_source/clang/lib/CodeGen/CGVTT.cpp", 149, __PRETTY_FUNCTION__))" file_link="../../../include/assert.h.html#88" macro="true">assert(I != SubVTTIndicies.end() && "Did not find index!");
150
151  return I->second;
152}
153
154uint64_t
155CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
156                                                BaseSubobject Base) {
157  SecondaryVirtualPointerIndicesMapTy::iterator I =
158    SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
159
160  if (I != SecondaryVirtualPointerIndices.end())
161    return I->second;
162
163  VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
164
165  // Insert all secondary vpointer indices.
166  for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
167       Builder.getSecondaryVirtualPointerIndices().begin(),
168       E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {
169    std::pair<const CXXRecordDecl *, BaseSubobject> Pair =
170      std::make_pair(RD, I->first);
171
172    SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
173  }
174
175  I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
176   (0) . __assert_fail ("I != SecondaryVirtualPointerIndices.end() && \"Did not find index!\"", "/home/seafit/code_projects/clang_source/clang/lib/CodeGen/CGVTT.cpp", 176, __PRETTY_FUNCTION__))" file_link="../../../include/assert.h.html#88" macro="true">assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");
177
178  return I->second;
179}
180
clang::CodeGen::CodeGenVTables::EmitVTTDefinition
clang::CodeGen::CodeGenVTables::GetAddrOfVTT
clang::CodeGen::CodeGenVTables::getSubVTTIndex
clang::CodeGen::CodeGenVTables::getSecondaryVirtualPointerIndex
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