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1 //===- SymbolTable.h --------------------------------------------*- C++ -*-===//
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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 #ifndef LLD_WASM_SYMBOL_TABLE_H
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10 #define LLD_WASM_SYMBOL_TABLE_H
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11
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12 #include "InputFiles.h"
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13 #include "LTO.h"
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14 #include "Symbols.h"
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15 #include "lld/Common/LLVM.h"
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16 #include "llvm/ADT/CachedHashString.h"
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17 #include "llvm/ADT/DenseSet.h"
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173
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18 #include "llvm/ADT/Optional.h"
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19 #include "llvm/BinaryFormat/WasmTraits.h"
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20
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21 namespace lld {
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22 namespace wasm {
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23
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24 class InputSegment;
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25
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26 // SymbolTable is a bucket of all known symbols, including defined,
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27 // undefined, or lazy symbols (the last one is symbols in archive
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28 // files whose archive members are not yet loaded).
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29 //
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30 // We put all symbols of all files to a SymbolTable, and the
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31 // SymbolTable selects the "best" symbols if there are name
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32 // conflicts. For example, obviously, a defined symbol is better than
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33 // an undefined symbol. Or, if there's a conflict between a lazy and a
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34 // undefined, it'll read an archive member to read a real definition
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35 // to replace the lazy symbol. The logic is implemented in the
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36 // add*() functions, which are called by input files as they are parsed.
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37 // There is one add* function per symbol type.
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38 class SymbolTable {
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39 public:
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40 void wrap(Symbol *sym, Symbol *real, Symbol *wrap);
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41
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42 void addFile(InputFile *file);
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43
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44 void addCombinedLTOObject();
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45
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46 ArrayRef<Symbol *> getSymbols() const { return symVector; }
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47
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48 Symbol *find(StringRef name);
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49
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50 void replace(StringRef name, Symbol* sym);
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51
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52 void trace(StringRef name);
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53
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54 Symbol *addDefinedFunction(StringRef name, uint32_t flags, InputFile *file,
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55 InputFunction *function);
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56 Symbol *addDefinedData(StringRef name, uint32_t flags, InputFile *file,
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57 InputChunk *segment, uint64_t address, uint64_t size);
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58 Symbol *addDefinedGlobal(StringRef name, uint32_t flags, InputFile *file,
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59 InputGlobal *g);
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60 Symbol *addDefinedTag(StringRef name, uint32_t flags, InputFile *file,
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61 InputTag *t);
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62 Symbol *addDefinedTable(StringRef name, uint32_t flags, InputFile *file,
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63 InputTable *t);
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64
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65 Symbol *addUndefinedFunction(StringRef name,
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66 llvm::Optional<StringRef> importName,
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67 llvm::Optional<StringRef> importModule,
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68 uint32_t flags, InputFile *file,
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69 const WasmSignature *signature,
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70 bool isCalledDirectly);
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71 Symbol *addUndefinedData(StringRef name, uint32_t flags, InputFile *file);
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72 Symbol *addUndefinedGlobal(StringRef name,
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73 llvm::Optional<StringRef> importName,
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74 llvm::Optional<StringRef> importModule,
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75 uint32_t flags, InputFile *file,
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76 const WasmGlobalType *type);
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77 Symbol *addUndefinedTable(StringRef name,
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78 llvm::Optional<StringRef> importName,
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79 llvm::Optional<StringRef> importModule,
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80 uint32_t flags, InputFile *file,
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81 const WasmTableType *type);
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82
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83 TableSymbol *resolveIndirectFunctionTable(bool required);
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84
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85 void addLazy(ArchiveFile *f, const llvm::object::Archive::Symbol *sym);
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86
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87 bool addComdat(StringRef name);
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88
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89 DefinedData *addSyntheticDataSymbol(StringRef name, uint32_t flags);
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90 DefinedGlobal *addSyntheticGlobal(StringRef name, uint32_t flags,
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91 InputGlobal *global);
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92 DefinedFunction *addSyntheticFunction(StringRef name, uint32_t flags,
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93 InputFunction *function);
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94 DefinedData *addOptionalDataSymbol(StringRef name, uint64_t value = 0);
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95 DefinedGlobal *addOptionalGlobalSymbol(StringRef name, InputGlobal *global);
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96 DefinedTable *addSyntheticTable(StringRef name, uint32_t flags,
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97 InputTable *global);
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98
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99 void handleSymbolVariants();
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100 void handleWeakUndefines();
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101 DefinedFunction *createUndefinedStub(const WasmSignature &sig);
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102
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103 std::vector<ObjFile *> objectFiles;
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104 std::vector<SharedFile *> sharedFiles;
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105 std::vector<BitcodeFile *> bitcodeFiles;
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106 std::vector<InputFunction *> syntheticFunctions;
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107 std::vector<InputGlobal *> syntheticGlobals;
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108 std::vector<InputTable *> syntheticTables;
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109
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110 private:
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111 std::pair<Symbol *, bool> insert(StringRef name, const InputFile *file);
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112 std::pair<Symbol *, bool> insertName(StringRef name);
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113
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114 bool getFunctionVariant(Symbol* sym, const WasmSignature *sig,
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115 const InputFile *file, Symbol **out);
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116 InputFunction *replaceWithUnreachable(Symbol *sym, const WasmSignature &sig,
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117 StringRef debugName);
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118 void replaceWithUndefined(Symbol *sym);
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119
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120 TableSymbol *createDefinedIndirectFunctionTable(StringRef name);
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121 TableSymbol *createUndefinedIndirectFunctionTable(StringRef name);
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122
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123 // Maps symbol names to index into the symVector. -1 means that symbols
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124 // is to not yet in the vector but it should have tracing enabled if it is
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125 // ever added.
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126 llvm::DenseMap<llvm::CachedHashStringRef, int> symMap;
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127 std::vector<Symbol *> symVector;
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128
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129 // For certain symbols types, e.g. function symbols, we allow for multiple
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130 // variants of the same symbol with different signatures.
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131 llvm::DenseMap<llvm::CachedHashStringRef, std::vector<Symbol *>> symVariants;
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132 llvm::DenseMap<WasmSignature, DefinedFunction *> stubFunctions;
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133
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134 // Comdat groups define "link once" sections. If two comdat groups have the
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135 // same name, only one of them is linked, and the other is ignored. This set
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136 // is used to uniquify them.
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137 llvm::DenseSet<llvm::CachedHashStringRef> comdatGroups;
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138
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139 // For LTO.
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140 std::unique_ptr<BitcodeCompiler> lto;
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141 };
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142
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143 extern SymbolTable *symtab;
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144
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145 } // namespace wasm
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146 } // namespace lld
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147
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148 #endif
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