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1 //===------- ItaniumCXXABI.cpp - AST support for the Itanium C++ ABI ------===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8 //
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9 // This provides C++ AST support targeting the Itanium C++ ABI, which is
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10 // documented at:
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11 // http://www.codesourcery.com/public/cxx-abi/abi.html
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12 // http://www.codesourcery.com/public/cxx-abi/abi-eh.html
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13 //
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14 // It also supports the closely-related ARM C++ ABI, documented at:
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15 // http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf
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16 //
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17 //===----------------------------------------------------------------------===//
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18
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19 #include "CXXABI.h"
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20 #include "clang/AST/ASTContext.h"
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21 #include "clang/AST/DeclCXX.h"
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22 #include "clang/AST/Mangle.h"
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23 #include "clang/AST/MangleNumberingContext.h"
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24 #include "clang/AST/RecordLayout.h"
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25 #include "clang/AST/Type.h"
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26 #include "clang/Basic/TargetInfo.h"
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27 #include "llvm/ADT/FoldingSet.h"
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28 #include "llvm/ADT/iterator.h"
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29
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30 using namespace clang;
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31
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32 namespace {
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33
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34 /// According to Itanium C++ ABI 5.1.2:
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35 /// the name of an anonymous union is considered to be
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36 /// the name of the first named data member found by a pre-order,
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37 /// depth-first, declaration-order walk of the data members of
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38 /// the anonymous union.
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39 /// If there is no such data member (i.e., if all of the data members
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40 /// in the union are unnamed), then there is no way for a program to
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41 /// refer to the anonymous union, and there is therefore no need to mangle its name.
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42 ///
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43 /// Returns the name of anonymous union VarDecl or nullptr if it is not found.
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44 static const IdentifierInfo *findAnonymousUnionVarDeclName(const VarDecl& VD) {
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45 const RecordType *RT = VD.getType()->getAs<RecordType>();
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46 assert(RT && "type of VarDecl is expected to be RecordType.");
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47 assert(RT->getDecl()->isUnion() && "RecordType is expected to be a union.");
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48 if (const FieldDecl *FD = RT->getDecl()->findFirstNamedDataMember()) {
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49 return FD->getIdentifier();
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50 }
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51
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52 return nullptr;
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53 }
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54
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55 /// The name of a decomposition declaration.
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56 struct DecompositionDeclName {
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57 using BindingArray = ArrayRef<const BindingDecl*>;
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58
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59 /// Representative example of a set of bindings with these names.
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60 BindingArray Bindings;
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61
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62 /// Iterators over the sequence of identifiers in the name.
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63 struct Iterator
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64 : llvm::iterator_adaptor_base<Iterator, BindingArray::const_iterator,
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65 std::random_access_iterator_tag,
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66 const IdentifierInfo *> {
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67 Iterator(BindingArray::const_iterator It) : iterator_adaptor_base(It) {}
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68 const IdentifierInfo *operator*() const {
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69 return (*this->I)->getIdentifier();
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70 }
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71 };
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72 Iterator begin() const { return Iterator(Bindings.begin()); }
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73 Iterator end() const { return Iterator(Bindings.end()); }
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74 };
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75 }
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76
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77 namespace llvm {
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78 template<typename T> bool isDenseMapKeyEmpty(T V) {
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79 return llvm::DenseMapInfo<T>::isEqual(
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80 V, llvm::DenseMapInfo<T>::getEmptyKey());
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81 }
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82 template<typename T> bool isDenseMapKeyTombstone(T V) {
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83 return llvm::DenseMapInfo<T>::isEqual(
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84 V, llvm::DenseMapInfo<T>::getTombstoneKey());
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85 }
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86
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87 template<typename T>
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88 Optional<bool> areDenseMapKeysEqualSpecialValues(T LHS, T RHS) {
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89 bool LHSEmpty = isDenseMapKeyEmpty(LHS);
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90 bool RHSEmpty = isDenseMapKeyEmpty(RHS);
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91 if (LHSEmpty || RHSEmpty)
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92 return LHSEmpty && RHSEmpty;
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93
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94 bool LHSTombstone = isDenseMapKeyTombstone(LHS);
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95 bool RHSTombstone = isDenseMapKeyTombstone(RHS);
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96 if (LHSTombstone || RHSTombstone)
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97 return LHSTombstone && RHSTombstone;
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98
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99 return None;
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100 }
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101
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102 template<>
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103 struct DenseMapInfo<DecompositionDeclName> {
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104 using ArrayInfo = llvm::DenseMapInfo<ArrayRef<const BindingDecl*>>;
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105 static DecompositionDeclName getEmptyKey() {
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106 return {ArrayInfo::getEmptyKey()};
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107 }
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108 static DecompositionDeclName getTombstoneKey() {
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109 return {ArrayInfo::getTombstoneKey()};
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110 }
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111 static unsigned getHashValue(DecompositionDeclName Key) {
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112 assert(!isEqual(Key, getEmptyKey()) && !isEqual(Key, getTombstoneKey()));
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113 return llvm::hash_combine_range(Key.begin(), Key.end());
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114 }
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115 static bool isEqual(DecompositionDeclName LHS, DecompositionDeclName RHS) {
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116 if (Optional<bool> Result = areDenseMapKeysEqualSpecialValues(
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117 LHS.Bindings, RHS.Bindings))
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118 return *Result;
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119
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120 return LHS.Bindings.size() == RHS.Bindings.size() &&
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121 std::equal(LHS.begin(), LHS.end(), RHS.begin());
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122 }
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123 };
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124 }
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125
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126 namespace {
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127
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128 /// Keeps track of the mangled names of lambda expressions and block
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129 /// literals within a particular context.
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130 class ItaniumNumberingContext : public MangleNumberingContext {
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131 ItaniumMangleContext *Mangler;
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132 llvm::StringMap<unsigned> LambdaManglingNumbers;
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133 unsigned BlockManglingNumber = 0;
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134 llvm::DenseMap<const IdentifierInfo *, unsigned> VarManglingNumbers;
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135 llvm::DenseMap<const IdentifierInfo *, unsigned> TagManglingNumbers;
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136 llvm::DenseMap<DecompositionDeclName, unsigned>
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137 DecompsitionDeclManglingNumbers;
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138
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139 public:
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140 ItaniumNumberingContext(ItaniumMangleContext *Mangler) : Mangler(Mangler) {}
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141
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142 unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {
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143 const CXXRecordDecl *Lambda = CallOperator->getParent();
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144 assert(Lambda->isLambda());
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145
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146 // Computation of the <lambda-sig> is non-trivial and subtle. Rather than
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147 // duplicating it here, just mangle the <lambda-sig> directly.
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148 llvm::SmallString<128> LambdaSig;
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149 llvm::raw_svector_ostream Out(LambdaSig);
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150 Mangler->mangleLambdaSig(Lambda, Out);
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151
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152 return ++LambdaManglingNumbers[LambdaSig];
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153 }
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154
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155 unsigned getManglingNumber(const BlockDecl *BD) override {
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156 return ++BlockManglingNumber;
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157 }
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158
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159 unsigned getStaticLocalNumber(const VarDecl *VD) override {
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160 return 0;
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161 }
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162
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163 /// Variable decls are numbered by identifier.
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164 unsigned getManglingNumber(const VarDecl *VD, unsigned) override {
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165 if (auto *DD = dyn_cast<DecompositionDecl>(VD)) {
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166 DecompositionDeclName Name{DD->bindings()};
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167 return ++DecompsitionDeclManglingNumbers[Name];
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168 }
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169
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170 const IdentifierInfo *Identifier = VD->getIdentifier();
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171 if (!Identifier) {
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172 // VarDecl without an identifier represents an anonymous union
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173 // declaration.
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174 Identifier = findAnonymousUnionVarDeclName(*VD);
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175 }
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176 return ++VarManglingNumbers[Identifier];
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177 }
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178
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179 unsigned getManglingNumber(const TagDecl *TD, unsigned) override {
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180 return ++TagManglingNumbers[TD->getIdentifier()];
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181 }
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182 };
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183
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184 class ItaniumCXXABI : public CXXABI {
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185 private:
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186 std::unique_ptr<MangleContext> Mangler;
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187 protected:
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188 ASTContext &Context;
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189 public:
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190 ItaniumCXXABI(ASTContext &Ctx)
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191 : Mangler(Ctx.createMangleContext()), Context(Ctx) {}
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192
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193 MemberPointerInfo
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194 getMemberPointerInfo(const MemberPointerType *MPT) const override {
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195 const TargetInfo &Target = Context.getTargetInfo();
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196 TargetInfo::IntType PtrDiff = Target.getPtrDiffType(0);
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197 MemberPointerInfo MPI;
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198 MPI.Width = Target.getTypeWidth(PtrDiff);
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199 MPI.Align = Target.getTypeAlign(PtrDiff);
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200 MPI.HasPadding = false;
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201 if (MPT->isMemberFunctionPointer())
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202 MPI.Width *= 2;
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203 return MPI;
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204 }
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205
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206 CallingConv getDefaultMethodCallConv(bool isVariadic) const override {
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207 const llvm::Triple &T = Context.getTargetInfo().getTriple();
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208 if (!isVariadic && T.isWindowsGNUEnvironment() &&
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209 T.getArch() == llvm::Triple::x86)
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210 return CC_X86ThisCall;
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211 return Context.getTargetInfo().getDefaultCallingConv();
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212 }
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213
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214 // We cheat and just check that the class has a vtable pointer, and that it's
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215 // only big enough to have a vtable pointer and nothing more (or less).
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216 bool isNearlyEmpty(const CXXRecordDecl *RD) const override {
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217
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218 // Check that the class has a vtable pointer.
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219 if (!RD->isDynamicClass())
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220 return false;
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221
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222 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
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223 CharUnits PointerSize =
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224 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
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225 return Layout.getNonVirtualSize() == PointerSize;
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226 }
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227
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228 const CXXConstructorDecl *
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229 getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {
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230 return nullptr;
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231 }
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232
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233 void addCopyConstructorForExceptionObject(CXXRecordDecl *RD,
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234 CXXConstructorDecl *CD) override {}
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235
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236 void addTypedefNameForUnnamedTagDecl(TagDecl *TD,
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237 TypedefNameDecl *DD) override {}
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238
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239 TypedefNameDecl *getTypedefNameForUnnamedTagDecl(const TagDecl *TD) override {
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240 return nullptr;
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241 }
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242
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243 void addDeclaratorForUnnamedTagDecl(TagDecl *TD,
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244 DeclaratorDecl *DD) override {}
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245
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246 DeclaratorDecl *getDeclaratorForUnnamedTagDecl(const TagDecl *TD) override {
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247 return nullptr;
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248 }
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249
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250 std::unique_ptr<MangleNumberingContext>
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251 createMangleNumberingContext() const override {
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252 return std::make_unique<ItaniumNumberingContext>(
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253 cast<ItaniumMangleContext>(Mangler.get()));
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254 }
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255 };
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256 }
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257
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258 CXXABI *clang::CreateItaniumCXXABI(ASTContext &Ctx) {
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259 return new ItaniumCXXABI(Ctx);
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260 }
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