lld/wasm/SymbolTable.h

   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