1//===--- FileIndex.h - Index for files. ---------------------------- 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// FileIndex implements SymbolIndex for symbols from a set of files. Symbols are
10// maintained at source-file granularity (e.g. with ASTs), and files can be
11// updated dynamically.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_FILEINDEX_H
16#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_FILEINDEX_H
17
18#include "Headers.h"
19#include "clang-include-cleaner/Record.h"
20#include "index/Index.h"
21#include "index/Merge.h"
22#include "index/Ref.h"
23#include "index/Relation.h"
24#include "index/Serialization.h"
25#include "index/Symbol.h"
26#include "support/MemoryTree.h"
27#include "support/Path.h"
28#include "clang/Lex/Preprocessor.h"
29#include "llvm/ADT/DenseSet.h"
30#include "llvm/ADT/StringMap.h"
31#include "llvm/ADT/StringRef.h"
32#include <memory>
33#include <optional>
34#include <vector>
35
36namespace clang {
37class ASTContext;
38namespace clangd {
39class ParsedAST;
40
41/// Select between in-memory index implementations, which have tradeoffs.
42enum class IndexType {
43 // MemIndex is trivially cheap to build, but has poor query performance.
44 Light,
45 // Dex is relatively expensive to build and uses more memory, but is fast.
46 Heavy,
47};
48
49/// How to handle duplicated symbols across multiple files.
50enum class DuplicateHandling {
51 // Pick a random symbol. Less accurate but faster.
52 PickOne,
53 // Merge symbols. More accurate but slower.
54 Merge,
55};
56
57/// A container of slabs associated with a key. It can be updated at key
58/// granularity, replacing all slabs belonging to a key with a new set. Keys are
59/// usually file paths/uris.
60///
61/// This implements snapshot semantics. Each update will create a new snapshot
62/// for all slabs of the Key. Snapshots are managed with shared pointers that
63/// are shared between this class and the users. For each key, this class only
64/// stores a pointer pointing to the newest snapshot, and an outdated snapshot
65/// is deleted by the last owner of the snapshot, either this class or the
66/// symbol index.
67///
68/// The snapshot semantics keeps critical sections minimal since we only need
69/// locking when we swap or obtain references to snapshots.
70class FileSymbols {
71public:
72 FileSymbols(IndexContents IdxContents);
73 /// Updates all slabs associated with the \p Key.
74 /// If either is nullptr, corresponding data for \p Key will be removed.
75 /// If CountReferences is true, \p Refs will be used for counting references
76 /// during merging.
77 void update(llvm::StringRef Key, std::unique_ptr<SymbolSlab> Symbols,
78 std::unique_ptr<RefSlab> Refs,
79 std::unique_ptr<RelationSlab> Relations, bool CountReferences);
80
81 /// The index keeps the slabs alive.
82 /// Will count Symbol::References based on number of references in the main
83 /// files, while building the index with DuplicateHandling::Merge option.
84 /// Version is populated with an increasing sequence counter.
85 std::unique_ptr<SymbolIndex>
86 buildIndex(IndexType,
87 DuplicateHandling DuplicateHandle = DuplicateHandling::PickOne,
88 size_t *Version = nullptr);
89
90 void profile(MemoryTree &MT) const;
91
92private:
93 IndexContents IdxContents;
94
95 struct RefSlabAndCountReferences {
96 std::shared_ptr<RefSlab> Slab;
97 bool CountReferences = false;
98 };
99 mutable std::mutex Mutex;
100
101 size_t Version = 0;
102 llvm::StringMap<std::shared_ptr<SymbolSlab>> SymbolsSnapshot;
103 llvm::StringMap<RefSlabAndCountReferences> RefsSnapshot;
104 llvm::StringMap<std::shared_ptr<RelationSlab>> RelationsSnapshot;
105};
106
107/// This manages symbols from files and an in-memory index on all symbols.
108/// FIXME: Expose an interface to remove files that are closed.
109class FileIndex : public MergedIndex {
110public:
111 FileIndex();
112
113 /// Update preamble symbols of file \p Path with all declarations in \p AST
114 /// and macros in \p PP.
115 void updatePreamble(PathRef Path, llvm::StringRef Version, ASTContext &AST,
116 Preprocessor &PP,
117 const include_cleaner::PragmaIncludes &PI);
118 void updatePreamble(IndexFileIn);
119
120 /// Update symbols and references from main file \p Path with
121 /// `indexMainDecls`.
122 void updateMain(PathRef Path, ParsedAST &AST);
123
124 void profile(MemoryTree &MT) const;
125
126private:
127 // Contains information from each file's preamble only. Symbols and relations
128 // are sharded per declaration file to deduplicate multiple symbols and reduce
129 // memory usage.
130 // Missing information:
131 // - symbol refs (these are always "from the main file")
132 // - definition locations in the main file
133 //
134 // Note that we store only one version of a header, hence symbols appearing in
135 // different PP states will be missing.
136 FileSymbols PreambleSymbols;
137 SwapIndex PreambleIndex;
138
139 // Contains information from each file's main AST.
140 // These are updated frequently (on file change), but are relatively small.
141 // Mostly contains:
142 // - refs to symbols declared in the preamble and referenced from main
143 // - symbols declared both in the main file and the preamble
144 // (Note that symbols *only* in the main file are not indexed).
145 FileSymbols MainFileSymbols;
146 SwapIndex MainFileIndex;
147
148 // While both the FileIndex and SwapIndex are threadsafe, we need to track
149 // versions to ensure that we don't overwrite newer indexes with older ones.
150 std::mutex UpdateIndexMu;
151 unsigned MainIndexVersion = 0;
152 unsigned PreambleIndexVersion = 0;
153};
154
155using SlabTuple = std::tuple<SymbolSlab, RefSlab, RelationSlab>;
156
157/// Retrieves symbols and refs of local top level decls in \p AST (i.e.
158/// `AST.getLocalTopLevelDecls()`).
159/// Exposed to assist in unit tests.
160SlabTuple indexMainDecls(ParsedAST &AST);
161
162/// Index declarations from \p AST and macros from \p PP that are declared in
163/// included headers.
164SlabTuple indexHeaderSymbols(llvm::StringRef Version, ASTContext &AST,
165 Preprocessor &PP,
166 const include_cleaner::PragmaIncludes &PI);
167
168/// Takes slabs coming from a TU (multiple files) and shards them per
169/// declaration location.
170struct FileShardedIndex {
171 /// \p HintPath is used to convert file URIs stored in symbols into absolute
172 /// paths.
173 explicit FileShardedIndex(IndexFileIn Input);
174
175 /// Returns uris for all files that has a shard.
176 std::vector<llvm::StringRef> getAllSources() const;
177
178 /// Generates index shard for the \p Uri. Note that this function results in
179 /// a copy of all the relevant data.
180 /// Returned index will always have Symbol/Refs/Relation Slabs set, even if
181 /// they are empty.
182 std::optional<IndexFileIn> getShard(llvm::StringRef Uri) const;
183
184private:
185 // Contains all the information that belongs to a single file.
186 struct FileShard {
187 // Either declared or defined in the file.
188 llvm::DenseSet<const Symbol *> Symbols;
189 // Reference occurs in the file.
190 llvm::DenseSet<const Ref *> Refs;
191 // Subject is declared in the file.
192 llvm::DenseSet<const Relation *> Relations;
193 // Contains edges for only the direct includes.
194 IncludeGraph IG;
195 };
196
197 // Keeps all the information alive.
198 const IndexFileIn Index;
199 // Mapping from URIs to slab information.
200 llvm::StringMap<FileShard> Shards;
201 // Used to build RefSlabs.
202 llvm::DenseMap<const Ref *, SymbolID> RefToSymID;
203};
204
205} // namespace clangd
206} // namespace clang
207
208#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_FILEINDEX_H
209

source code of clang-tools-extra/clangd/index/FileIndex.h