clang-tools  8.0.0
FileIndex.h
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1 //===--- FileIndex.h - Index for files. ---------------------------- C++-*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // FileIndex implements SymbolIndex for symbols from a set of files. Symbols are
11 // maintained at source-file granuality (e.g. with ASTs), and files can be
12 // updated dynamically.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_FILEINDEX_H
17 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_FILEINDEX_H
18 
19 #include "ClangdUnit.h"
20 #include "Index.h"
21 #include "MemIndex.h"
22 #include "Merge.h"
23 #include "clang/Lex/Preprocessor.h"
24 #include <memory>
25 
26 namespace clang {
27 namespace clangd {
28 
29 /// Select between in-memory index implementations, which have tradeoffs.
30 enum class IndexType {
31  // MemIndex is trivially cheap to build, but has poor query performance.
32  Light,
33  // Dex is relatively expensive to build and uses more memory, but is fast.
34  Heavy,
35 };
36 
37 /// How to handle duplicated symbols across multiple files.
38 enum class DuplicateHandling {
39  // Pick a random symbol. Less accurate but faster.
40  PickOne,
41  // Merge symbols. More accurate but slower.
42  Merge,
43 };
44 
45 /// A container of Symbols from several source files. It can be updated
46 /// at source-file granularity, replacing all symbols from one file with a new
47 /// set.
48 ///
49 /// This implements a snapshot semantics for symbols in a file. Each update to a
50 /// file will create a new snapshot for all symbols in the file. Snapshots are
51 /// managed with shared pointers that are shared between this class and the
52 /// users. For each file, this class only stores a pointer pointing to the
53 /// newest snapshot, and an outdated snapshot is deleted by the last owner of
54 /// the snapshot, either this class or the symbol index.
55 ///
56 /// The snapshot semantics keeps critical sections minimal since we only need
57 /// locking when we swap or obtain references to snapshots.
58 class FileSymbols {
59 public:
60  /// Updates all symbols and refs in a file.
61  /// If either is nullptr, corresponding data for \p Path will be removed.
62  void update(PathRef Path, std::unique_ptr<SymbolSlab> Slab,
63  std::unique_ptr<RefSlab> Refs);
64 
65  // The index keeps the symbols alive.
66  std::unique_ptr<SymbolIndex>
67  buildIndex(IndexType,
69 
70 private:
71  mutable std::mutex Mutex;
72 
73  /// Stores the latest symbol snapshots for all active files.
74  llvm::StringMap<std::shared_ptr<SymbolSlab>> FileToSymbols;
75  /// Stores the latest ref snapshots for all active files.
76  llvm::StringMap<std::shared_ptr<RefSlab>> FileToRefs;
77 };
78 
79 /// This manages symbols from files and an in-memory index on all symbols.
80 /// FIXME: Expose an interface to remove files that are closed.
81 class FileIndex : public MergedIndex {
82 public:
83  FileIndex(bool UseDex = true);
84 
85  /// Update preamble symbols of file \p Path with all declarations in \p AST
86  /// and macros in \p PP.
87  void updatePreamble(PathRef Path, ASTContext &AST,
88  std::shared_ptr<Preprocessor> PP);
89 
90  /// Update symbols and references from main file \p Path with
91  /// `indexMainDecls`.
92  void updateMain(PathRef Path, ParsedAST &AST);
93 
94 private:
95  bool UseDex; // FIXME: this should be always on.
96 
97  // Contains information from each file's preamble only.
98  // These are large, but update fairly infrequently (preambles are stable).
99  // Missing information:
100  // - symbol refs (these are always "from the main file")
101  // - definition locations in the main file
102  //
103  // FIXME: Because the preambles for different TUs have large overlap and
104  // FileIndex doesn't deduplicate, this uses lots of extra RAM.
105  // The biggest obstacle in fixing this: the obvious approach of partitioning
106  // by declaring file (rather than main file) fails if headers provide
107  // different symbols based on preprocessor state.
108  FileSymbols PreambleSymbols;
109  SwapIndex PreambleIndex;
110 
111  // Contains information from each file's main AST.
112  // These are updated frequently (on file change), but are relatively small.
113  // Mostly contains:
114  // - refs to symbols declared in the preamble and referenced from main
115  // - symbols declared both in the main file and the preamble
116  // (Note that symbols *only* in the main file are not indexed).
117  FileSymbols MainFileSymbols;
118  SwapIndex MainFileIndex;
119 };
120 
121 /// Retrieves symbols and refs of local top level decls in \p AST (i.e.
122 /// `AST.getLocalTopLevelDecls()`).
123 /// Exposed to assist in unit tests.
124 std::pair<SymbolSlab, RefSlab> indexMainDecls(ParsedAST &AST);
125 
126 /// Idex declarations from \p AST and macros from \p PP that are declared in
127 /// included headers.
128 SymbolSlab indexHeaderSymbols(ASTContext &AST,
129  std::shared_ptr<Preprocessor> PP);
130 
131 } // namespace clangd
132 } // namespace clang
133 
134 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_FILEINDEX_H
SymbolSlab indexHeaderSymbols(ASTContext &AST, std::shared_ptr< Preprocessor > PP)
Idex declarations from AST and macros from PP that are declared in included headers.
Definition: FileIndex.cpp:80
IndexType
Select between in-memory index implementations, which have tradeoffs.
Definition: FileIndex.h:30
A container of Symbols from several source files.
Definition: FileIndex.h:58
This manages symbols from files and an in-memory index on all symbols.
Definition: FileIndex.h:81
llvm::StringRef PathRef
A typedef to represent a ref to file path.
Definition: Path.h:24
static llvm::cl::opt< bool > UseDex("use-dex-index", llvm::cl::desc("Use experimental Dex dynamic index."), llvm::cl::init(false), llvm::cl::Hidden)
DuplicateHandling
How to handle duplicated symbols across multiple files.
Definition: FileIndex.h:38
std::pair< SymbolSlab, RefSlab > indexMainDecls(ParsedAST &AST)
Retrieves symbols and refs of local top level decls in AST (i.e.
Definition: FileIndex.cpp:74
std::string Path
A typedef to represent a file path.
Definition: Path.h:21
Stores and provides access to parsed AST.
Definition: ClangdUnit.h:71
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//