--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lld/ELF/SymbolTable.h	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,97 @@
+//===- SymbolTable.h --------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_ELF_SYMBOL_TABLE_H
+#define LLD_ELF_SYMBOL_TABLE_H
+
+#include "InputFiles.h"
+#include "Symbols.h"
+#include "lld/Common/Strings.h"
+#include "llvm/ADT/CachedHashString.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
+
+namespace lld {
+namespace elf {
+
+// SymbolTable is a bucket of all known symbols, including defined,
+// undefined, or lazy symbols (the last one is symbols in archive
+// files whose archive members are not yet loaded).
+//
+// We put all symbols of all files to a SymbolTable, and the
+// SymbolTable selects the "best" symbols if there are name
+// conflicts. For example, obviously, a defined symbol is better than
+// an undefined symbol. Or, if there's a conflict between a lazy and a
+// undefined, it'll read an archive member to read a real definition
+// to replace the lazy symbol. The logic is implemented in the
+// add*() functions, which are called by input files as they are parsed. There
+// is one add* function per symbol type.
+class SymbolTable {
+  struct FilterOutPlaceholder {
+    bool operator()(Symbol *S) const { return !S->isPlaceholder(); }
+  };
+  using iterator = llvm::filter_iterator<std::vector<Symbol *>::const_iterator,
+                                         FilterOutPlaceholder>;
+
+public:
+  llvm::iterator_range<iterator> symbols() const {
+    return llvm::make_filter_range(symVector, FilterOutPlaceholder());
+  }
+
+  void wrap(Symbol *sym, Symbol *real, Symbol *wrap);
+
+  Symbol *insert(StringRef name);
+
+  Symbol *addSymbol(const Symbol &newSym);
+
+  void scanVersionScript();
+
+  Symbol *find(StringRef name);
+
+  void handleDynamicList();
+
+  // Set of .so files to not link the same shared object file more than once.
+  llvm::DenseMap<StringRef, SharedFile *> soNames;
+
+  // Comdat groups define "link once" sections. If two comdat groups have the
+  // same name, only one of them is linked, and the other is ignored. This map
+  // is used to uniquify them.
+  llvm::DenseMap<llvm::CachedHashStringRef, const InputFile *> comdatGroups;
+
+private:
+  std::vector<Symbol *> findByVersion(SymbolVersion ver);
+  std::vector<Symbol *> findAllByVersion(SymbolVersion ver);
+
+  llvm::StringMap<std::vector<Symbol *>> &getDemangledSyms();
+  void assignExactVersion(SymbolVersion ver, uint16_t versionId,
+                          StringRef versionName);
+  void assignWildcardVersion(SymbolVersion ver, uint16_t versionId);
+
+  // The order the global symbols are in is not defined. We can use an arbitrary
+  // order, but it has to be reproducible. That is true even when cross linking.
+  // The default hashing of StringRef produces different results on 32 and 64
+  // bit systems so we use a map to a vector. That is arbitrary, deterministic
+  // but a bit inefficient.
+  // FIXME: Experiment with passing in a custom hashing or sorting the symbols
+  // once symbol resolution is finished.
+  llvm::DenseMap<llvm::CachedHashStringRef, int> symMap;
+  std::vector<Symbol *> symVector;
+
+  // A map from demangled symbol names to their symbol objects.
+  // This mapping is 1:N because two symbols with different versions
+  // can have the same name. We use this map to handle "extern C++ {}"
+  // directive in version scripts.
+  llvm::Optional<llvm::StringMap<std::vector<Symbol *>>> demangledSyms;
+};
+
+extern SymbolTable *symtab;
+
+} // namespace elf
+} // namespace lld
+
+#endif