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