e9262edf0d
Placeholders (-y and redirectSymbols removed versioned symbols) are very rare and the check just makes symbol table iteration slower. Most iterations filter out placeholders anyway, so this change just drops the filter behavior. For "Add symbols to symtabs", we need to ensure that redirectSymbols sets isUsedInRegularObj to false when making a symbol placeholder, to avoid an assertion failure in SymbolTableSection<ELFT>::writeTo. My .text is 2KiB smaller. The speed-up linking chrome is 0.x%.
92 lines
3.5 KiB
C++
92 lines
3.5 KiB
C++
//===- SymbolTable.h --------------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLD_ELF_SYMBOL_TABLE_H
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#define LLD_ELF_SYMBOL_TABLE_H
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#include "InputFiles.h"
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#include "Symbols.h"
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#include "lld/Common/Strings.h"
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#include "llvm/ADT/CachedHashString.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/STLExtras.h"
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namespace lld {
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namespace elf {
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// SymbolTable is a bucket of all known symbols, including defined,
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// undefined, or lazy symbols (the last one is symbols in archive
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// files whose archive members are not yet loaded).
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//
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// We put all symbols of all files to a SymbolTable, and the
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// SymbolTable selects the "best" symbols if there are name
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// conflicts. For example, obviously, a defined symbol is better than
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// an undefined symbol. Or, if there's a conflict between a lazy and a
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// undefined, it'll read an archive member to read a real definition
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// to replace the lazy symbol. The logic is implemented in the
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// add*() functions, which are called by input files as they are parsed. There
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// is one add* function per symbol type.
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class SymbolTable {
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public:
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ArrayRef<Symbol *> symbols() const { return symVector; }
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void wrap(Symbol *sym, Symbol *real, Symbol *wrap);
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Symbol *insert(StringRef name);
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Symbol *addSymbol(const Symbol &newSym);
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void scanVersionScript();
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Symbol *find(StringRef name);
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void handleDynamicList();
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// Set of .so files to not link the same shared object file more than once.
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llvm::DenseMap<StringRef, SharedFile *> soNames;
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// Comdat groups define "link once" sections. If two comdat groups have the
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// same name, only one of them is linked, and the other is ignored. This map
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// is used to uniquify them.
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llvm::DenseMap<llvm::CachedHashStringRef, const InputFile *> comdatGroups;
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private:
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SmallVector<Symbol *, 0> findByVersion(SymbolVersion ver);
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SmallVector<Symbol *, 0> findAllByVersion(SymbolVersion ver,
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bool includeNonDefault);
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llvm::StringMap<SmallVector<Symbol *, 0>> &getDemangledSyms();
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bool assignExactVersion(SymbolVersion ver, uint16_t versionId,
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StringRef versionName, bool includeNonDefault);
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void assignWildcardVersion(SymbolVersion ver, uint16_t versionId,
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bool includeNonDefault);
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// The order the global symbols are in is not defined. We can use an arbitrary
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// order, but it has to be reproducible. That is true even when cross linking.
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// The default hashing of StringRef produces different results on 32 and 64
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// bit systems so we use a map to a vector. That is arbitrary, deterministic
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// but a bit inefficient.
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// FIXME: Experiment with passing in a custom hashing or sorting the symbols
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// once symbol resolution is finished.
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llvm::DenseMap<llvm::CachedHashStringRef, int> symMap;
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SmallVector<Symbol *, 0> symVector;
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// A map from demangled symbol names to their symbol objects.
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// This mapping is 1:N because two symbols with different versions
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// can have the same name. We use this map to handle "extern C++ {}"
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// directive in version scripts.
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llvm::Optional<llvm::StringMap<SmallVector<Symbol *, 0>>> demangledSyms;
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};
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extern std::unique_ptr<SymbolTable> symtab;
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} // namespace elf
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} // namespace lld
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#endif
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