Resolver.h revision 341825 
1//===- Core/Resolver.h - Resolves Atom References -------------------------===//
2//
3//                             The LLVM Linker
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef LLD_CORE_RESOLVER_H
11#define LLD_CORE_RESOLVER_H
12
13#include "lld/Core/ArchiveLibraryFile.h"
14#include "lld/Core/File.h"
15#include "lld/Core/SharedLibraryFile.h"
16#include "lld/Core/Simple.h"
17#include "lld/Core/SymbolTable.h"
18#include "llvm/ADT/DenseMap.h"
19#include "llvm/ADT/DenseSet.h"
20#include "llvm/Support/ErrorOr.h"
21#include <set>
22#include <unordered_map>
23#include <unordered_set>
24#include <vector>
25
26namespace lld {
27
28class Atom;
29class LinkingContext;
30
31/// The Resolver is responsible for merging all input object files
32/// and producing a merged graph.
33class Resolver {
34public:
35  Resolver(LinkingContext &ctx) : _ctx(ctx), _result(new MergedFile()) {}
36
37  // InputFiles::Handler methods
38  void doDefinedAtom(OwningAtomPtr<DefinedAtom> atom);
39  bool doUndefinedAtom(OwningAtomPtr<UndefinedAtom> atom);
40  void doSharedLibraryAtom(OwningAtomPtr<SharedLibraryAtom> atom);
41  void doAbsoluteAtom(OwningAtomPtr<AbsoluteAtom> atom);
42
43  // Handle files, this adds atoms from the current file thats
44  // being processed by the resolver
45  llvm::Expected<bool> handleFile(File &);
46
47  // Handle an archive library file.
48  llvm::Expected<bool> handleArchiveFile(File &);
49
50  // Handle a shared library file.
51  llvm::Error handleSharedLibrary(File &);
52
53  /// do work of merging and resolving and return list
54  bool resolve();
55
56  std::unique_ptr<SimpleFile> resultFile() { return std::move(_result); }
57
58private:
59  typedef std::function<llvm::Expected<bool>(StringRef)> UndefCallback;
60
61  bool undefinesAdded(int begin, int end);
62  File *getFile(int &index);
63
64  /// The main function that iterates over the files to resolve
65  bool resolveUndefines();
66  void updateReferences();
67  void deadStripOptimize();
68  bool checkUndefines();
69  void removeCoalescedAwayAtoms();
70  llvm::Expected<bool> forEachUndefines(File &file, UndefCallback callback);
71
72  void markLive(const Atom *atom);
73
74  class MergedFile : public SimpleFile {
75  public:
76    MergedFile() : SimpleFile("<linker-internal>", kindResolverMergedObject) {}
77    void addAtoms(llvm::MutableArrayRef<OwningAtomPtr<Atom>> atoms);
78  };
79
80  LinkingContext &_ctx;
81  SymbolTable _symbolTable;
82  std::vector<OwningAtomPtr<Atom>>     _atoms;
83  std::set<const Atom *>        _deadStripRoots;
84  llvm::DenseSet<const Atom *>  _liveAtoms;
85  llvm::DenseSet<const Atom *>  _deadAtoms;
86  std::unique_ptr<MergedFile>   _result;
87  std::unordered_multimap<const Atom *, const Atom *> _reverseRef;
88
89  // --start-group and --end-group
90  std::vector<File *> _files;
91  std::map<File *, bool> _newUndefinesAdded;
92
93  // List of undefined symbols.
94  std::vector<StringRef> _undefines;
95
96  // Start position in _undefines for each archive/shared library file.
97  // Symbols from index 0 to the start position are already searched before.
98  // Searching them again would never succeed. When we look for undefined
99  // symbols from an archive/shared library file, start from its start
100  // position to save time.
101  std::map<File *, size_t> _undefineIndex;
102};
103
104} // namespace lld
105
106#endif // LLD_CORE_RESOLVER_H
107