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
21namespace lld::wasm {
22
23class 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.
37class SymbolTable {
38public:
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 *addDefinedFunction(StringRef name, uint32_t flags, InputFile *file,
54 InputFunction *function);
55 Symbol *addDefinedData(StringRef name, uint32_t flags, InputFile *file,
56 InputChunk *segment, uint64_t address, uint64_t size);
57 Symbol *addDefinedGlobal(StringRef name, uint32_t flags, InputFile *file,
58 InputGlobal *g);
59 Symbol *addDefinedTag(StringRef name, uint32_t flags, InputFile *file,
60 InputTag *t);
61 Symbol *addDefinedTable(StringRef name, uint32_t flags, InputFile *file,
62 InputTable *t);
63
64 Symbol *addUndefinedFunction(StringRef name,
65 std::optional<StringRef> importName,
66 std::optional<StringRef> importModule,
67 uint32_t flags, InputFile *file,
68 const WasmSignature *signature,
69 bool isCalledDirectly);
70 Symbol *addUndefinedData(StringRef name, uint32_t flags, InputFile *file);
71 Symbol *addUndefinedGlobal(StringRef name,
72 std::optional<StringRef> importName,
73 std::optional<StringRef> importModule,
74 uint32_t flags, InputFile *file,
75 const WasmGlobalType *type);
76 Symbol *addUndefinedTable(StringRef name, std::optional<StringRef> importName,
77 std::optional<StringRef> importModule,
78 uint32_t flags, InputFile *file,
79 const WasmTableType *type);
80 Symbol *addUndefinedTag(StringRef name, std::optional<StringRef> importName,
81 std::optional<StringRef> importModule, uint32_t flags,
82 InputFile *file, const WasmSignature *sig);
83
84 TableSymbol *resolveIndirectFunctionTable(bool required);
85
86 void addLazy(StringRef name, InputFile *f);
87
88 bool addComdat(StringRef name);
89
90 DefinedData *addSyntheticDataSymbol(StringRef name, uint32_t flags);
91 DefinedGlobal *addSyntheticGlobal(StringRef name, uint32_t flags,
92 InputGlobal *global);
93 DefinedFunction *addSyntheticFunction(StringRef name, uint32_t flags,
94 InputFunction *function);
95 DefinedData *addOptionalDataSymbol(StringRef name, uint64_t value = 0);
96 DefinedGlobal *addOptionalGlobalSymbol(StringRef name, InputGlobal *global);
97 DefinedTable *addSyntheticTable(StringRef name, uint32_t flags,
98 InputTable *global);
99
100 void handleSymbolVariants();
101 void handleWeakUndefines();
102 DefinedFunction *createUndefinedStub(const WasmSignature &sig);
103
104private:
105 std::pair<Symbol *, bool> insert(StringRef name, const InputFile *file);
106 std::pair<Symbol *, bool> insertName(StringRef name);
107
108 bool getFunctionVariant(Symbol* sym, const WasmSignature *sig,
109 const InputFile *file, Symbol **out);
110 InputFunction *replaceWithUnreachable(Symbol *sym, const WasmSignature &sig,
111 StringRef debugName);
112 void replaceWithUndefined(Symbol *sym);
113
114 TableSymbol *createDefinedIndirectFunctionTable(StringRef name);
115 TableSymbol *createUndefinedIndirectFunctionTable(StringRef name);
116
117 // Maps symbol names to index into the symVector. -1 means that symbols
118 // is to not yet in the vector but it should have tracing enabled if it is
119 // ever added.
120 llvm::DenseMap<llvm::CachedHashStringRef, int> symMap;
121 std::vector<Symbol *> symVector;
122
123 // For certain symbols types, e.g. function symbols, we allow for multiple
124 // variants of the same symbol with different signatures.
125 llvm::DenseMap<llvm::CachedHashStringRef, std::vector<Symbol *>> symVariants;
126 llvm::DenseMap<WasmSignature, DefinedFunction *> stubFunctions;
127
128 // Comdat groups define "link once" sections. If two comdat groups have the
129 // same name, only one of them is linked, and the other is ignored. This set
130 // is used to uniquify them.
131 llvm::DenseSet<llvm::CachedHashStringRef> comdatGroups;
132
133 // For LTO.
134 std::unique_ptr<BitcodeCompiler> lto;
135};
136
137extern SymbolTable *symtab;
138
139} // namespace lld::wasm
140
141#endif
142

source code of lld/wasm/SymbolTable.h