clang-tools 18.0.0git
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1//===--- Preamble.h - Reusing expensive parts of the AST ---------*- C++-*-===//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
9// The vast majority of code in a typical translation unit is in the headers
10// included at the top of the file.
12// The preamble optimization says that we can parse this code once, and reuse
13// the result multiple times. The preamble is invalidated by changes to the
14// code in the preamble region, to the compile command, or to files on disk.
16// This is the most important optimization in clangd: it allows operations like
17// code-completion to have sub-second latency. It is supported by the
18// PrecompiledPreamble functionality in clang, which wraps the techniques used
19// by PCH files, modules etc into a convenient interface.
25#include "CollectMacros.h"
26#include "Compiler.h"
27#include "Diagnostics.h"
28#include "FS.h"
29#include "Headers.h"
30#include "clang-include-cleaner/Record.h"
31#include "support/Path.h"
32#include "clang/Basic/SourceManager.h"
33#include "clang/Frontend/CompilerInvocation.h"
34#include "clang/Frontend/PrecompiledPreamble.h"
35#include "clang/Lex/Lexer.h"
36#include "clang/Tooling/CompilationDatabase.h"
37#include "llvm/ADT/ArrayRef.h"
38#include "llvm/ADT/StringRef.h"
40#include <cstddef>
41#include <functional>
42#include <memory>
43#include <string>
44#include <utility>
45#include <vector>
47namespace clang {
48namespace clangd {
50/// The captured AST context.
51/// Keeps necessary structs for an ASTContext and Preprocessor alive.
52/// This enables consuming them after context that produced the AST is gone.
53/// (e.g. indexing a preamble ast on a separate thread). ASTContext stored
54/// inside is still not thread-safe.
58 CapturedASTCtx(CompilerInstance &Clang)
59 : Invocation(Clang.getInvocationPtr()),
60 Diagnostics(Clang.getDiagnosticsPtr()), Target(Clang.getTargetPtr()),
61 AuxTarget(Clang.getAuxTarget()), FileMgr(Clang.getFileManagerPtr()),
62 SourceMgr(Clang.getSourceManagerPtr()), PP(Clang.getPreprocessorPtr()),
63 Context(Clang.getASTContextPtr()) {}
65 CapturedASTCtx(const CapturedASTCtx &) = delete;
70 ASTContext &getASTContext() { return *Context; }
71 Preprocessor &getPreprocessor() { return *PP; }
72 CompilerInvocation &getCompilerInvocation() { return *Invocation; }
73 FileManager &getFileManager() { return *FileMgr; }
74 void setStatCache(std::shared_ptr<PreambleFileStatusCache> StatCache) {
75 this->StatCache = StatCache;
76 }
79 std::shared_ptr<CompilerInvocation> Invocation;
80 IntrusiveRefCntPtr<DiagnosticsEngine> Diagnostics;
81 IntrusiveRefCntPtr<TargetInfo> Target;
82 IntrusiveRefCntPtr<TargetInfo> AuxTarget;
83 IntrusiveRefCntPtr<FileManager> FileMgr;
84 IntrusiveRefCntPtr<SourceManager> SourceMgr;
85 std::shared_ptr<Preprocessor> PP;
86 IntrusiveRefCntPtr<ASTContext> Context;
87 std::shared_ptr<PreambleFileStatusCache> StatCache;
90/// The parsed preamble and associated data.
92/// As we must avoid re-parsing the preamble, any information that can only
93/// be obtained during parsing must be eagerly captured and stored here.
95 PreambleData(PrecompiledPreamble Preamble) : Preamble(std::move(Preamble)) {}
97 // Version of the ParseInputs this preamble was built from.
98 std::string Version;
99 tooling::CompileCommand CompileCommand;
100 PrecompiledPreamble Preamble;
101 std::vector<Diag> Diags;
102 // Processes like code completions and go-to-definitions will need #include
103 // information, and their compile action skips preamble range.
105 // Captures #include-mapping information in #included headers.
106 std::shared_ptr<const include_cleaner::PragmaIncludes> Pragmas;
107 // Macros defined in the preamble section of the main file.
108 // Users care about headers vs main-file, not preamble vs non-preamble.
109 // These should be treated as main-file entities e.g. for code completion.
111 // Pragma marks defined in the preamble section of the main file.
112 std::vector<PragmaMark> Marks;
113 // Cache of FS operations performed when building the preamble.
114 // When reusing a preamble, this cache can be consumed to save IO.
115 std::shared_ptr<PreambleFileStatusCache> StatCache;
116 // Whether there was a (possibly-incomplete) include-guard on the main file.
117 // We need to propagate this information "by hand" to subsequent parses.
122 std::function<void(CapturedASTCtx ASTCtx,
123 std::shared_ptr<const include_cleaner::PragmaIncludes>)>;
125/// Timings and statistics from the premble build. Unlike PreambleData, these
126/// do not need to be stored for later, but can be useful for logging, metrics,
127/// etc.
129 /// Total wall time it took to build preamble, in seconds.
131 /// Time spent in filesystem operations during the build, in seconds.
134 /// Estimate of the memory used while building the preamble.
135 /// This memory has been released when buildPreamble returns.
136 /// For example, this includes the size of the in-memory AST (ASTContext).
137 size_t BuildSize;
138 /// The serialized size of the preamble.
139 /// This storage is needed while the preamble is used (but may be on disk).
143/// Build a preamble for the new inputs unless an old one can be reused.
144/// If \p PreambleCallback is set, it will be run on top of the AST while
145/// building the preamble.
146/// If Stats is not non-null, build statistics will be exported there.
147std::shared_ptr<const PreambleData>
148buildPreamble(PathRef FileName, CompilerInvocation CI,
149 const ParseInputs &Inputs, bool StoreInMemory,
150 PreambleParsedCallback PreambleCallback,
151 PreambleBuildStats *Stats = nullptr);
153/// Returns true if \p Preamble is reusable for \p Inputs. Note that it will
154/// return true when some missing headers are now available.
155/// FIXME: Should return more information about the delta between \p Preamble
156/// and \p Inputs, e.g. new headers.
158 const ParseInputs &Inputs, PathRef FileName,
159 const CompilerInvocation &CI);
161/// Stores information required to parse a TU using a (possibly stale) Baseline
162/// preamble. Later on this information can be injected into the main file by
163/// updating compiler invocation with \c apply. This injected section
164/// approximately reflects additions to the preamble in Modified contents, e.g.
165/// new include directives.
169 /// \p Preamble is used verbatim.
171 /// Builds a patch that contains new PP directives introduced to the preamble
172 /// section of \p Modified compared to \p Baseline.
173 /// FIXME: This only handles include directives, we should at least handle
174 /// define/undef.
175 static PreamblePatch createFullPatch(llvm::StringRef FileName,
176 const ParseInputs &Modified,
177 const PreambleData &Baseline);
178 static PreamblePatch createMacroPatch(llvm::StringRef FileName,
179 const ParseInputs &Modified,
180 const PreambleData &Baseline);
181 /// Returns the FileEntry for the preamble patch of MainFilePath in SM, if
182 /// any.
183 static OptionalFileEntryRef getPatchEntry(llvm::StringRef MainFilePath,
184 const SourceManager &SM);
186 /// Adjusts CI (which compiles the modified inputs) to be used with the
187 /// baseline preamble. This is done by inserting an artificial include to the
188 /// \p CI that contains new directives calculated in create.
189 void apply(CompilerInvocation &CI) const;
191 /// Returns #include directives from the \c Modified preamble that were
192 /// resolved using the \c Baseline preamble. This covers the new locations of
193 /// inclusions that were moved around, but not inclusions of new files. Those
194 /// will be recorded when parsing the main file: the includes in the injected
195 /// section will be resolved back to their spelled positions in the main file
196 /// using the presumed-location mechanism.
197 std::vector<Inclusion> preambleIncludes() const;
199 /// Returns preamble bounds for the Modified.
200 PreambleBounds modifiedBounds() const { return ModifiedBounds; }
202 /// Returns textual patch contents.
203 llvm::StringRef text() const { return PatchContents; }
205 /// Returns diag locations for Modified contents.
206 llvm::ArrayRef<Diag> patchedDiags() const { return PatchedDiags; }
208 static constexpr llvm::StringLiteral HeaderName = "__preamble_patch__.h";
210 llvm::ArrayRef<PragmaMark> marks() const;
211 const MainFileMacros &mainFileMacros() const;
214 static PreamblePatch create(llvm::StringRef FileName,
215 const ParseInputs &Modified,
216 const PreambleData &Baseline,
219 PreamblePatch() = default;
220 std::string PatchContents;
221 std::string PatchFileName;
222 // Includes that are present in both Baseline and Modified. Used for
223 // patching includes of baseline preamble.
224 std::vector<Inclusion> PreambleIncludes;
225 // Diags that were attached to a line preserved in Modified contents.
226 std::vector<Diag> PatchedDiags;
227 PreambleBounds ModifiedBounds = {0, false};
228 const PreambleData *Baseline = nullptr;
229 std::vector<PragmaMark> PatchedMarks;
230 MainFileMacros PatchedMacros;
233} // namespace clangd
234} // namespace clang
std::unique_ptr< CompilerInstance > Clang
StringRef FileName
std::unique_ptr< CompilerInvocation > CI
A context is an immutable container for per-request data that must be propagated through layers that ...
Definition: Context.h:69
Stores information required to parse a TU using a (possibly stale) Baseline preamble.
Definition: Preamble.h:166
static OptionalFileEntryRef getPatchEntry(llvm::StringRef MainFilePath, const SourceManager &SM)
Returns the FileEntry for the preamble patch of MainFilePath in SM, if any.
Definition: Preamble.cpp:956
const MainFileMacros & mainFileMacros() const
Definition: Preamble.cpp:950
llvm::ArrayRef< PragmaMark > marks() const
Definition: Preamble.cpp:944
void apply(CompilerInvocation &CI) const
Adjusts CI (which compiles the modified inputs) to be used with the baseline preamble.
Definition: Preamble.cpp:915
static PreamblePatch unmodified(const PreambleData &Preamble)
Preamble is used verbatim.
Definition: Preamble.cpp:935
llvm::ArrayRef< Diag > patchedDiags() const
Returns diag locations for Modified contents.
Definition: Preamble.h:206
llvm::StringRef text() const
Returns textual patch contents.
Definition: Preamble.h:203
static PreamblePatch createMacroPatch(llvm::StringRef FileName, const ParseInputs &Modified, const PreambleData &Baseline)
Definition: Preamble.cpp:909
static PreamblePatch createFullPatch(llvm::StringRef FileName, const ParseInputs &Modified, const PreambleData &Baseline)
Builds a patch that contains new PP directives introduced to the preamble section of Modified compare...
Definition: Preamble.cpp:903
static constexpr llvm::StringLiteral HeaderName
Definition: Preamble.h:208
std::vector< Inclusion > preambleIncludes() const
Returns #include directives from the Modified preamble that were resolved using the Baseline preamble...
Definition: Preamble.cpp:931
PreambleBounds modifiedBounds() const
Returns preamble bounds for the Modified.
Definition: Preamble.h:200
std::function< void(CapturedASTCtx ASTCtx, std::shared_ptr< const include_cleaner::PragmaIncludes >)> PreambleParsedCallback
Definition: Preamble.h:123
bool isPreambleCompatible(const PreambleData &Preamble, const ParseInputs &Inputs, PathRef FileName, const CompilerInvocation &CI)
Returns true if Preamble is reusable for Inputs.
Definition: Preamble.cpp:730
std::shared_ptr< const PreambleData > buildPreamble(PathRef FileName, CompilerInvocation CI, const ParseInputs &Inputs, bool StoreInMemory, PreambleParsedCallback PreambleCallback, PreambleBuildStats *Stats)
Build a preamble for the new inputs unless an old one can be reused.
Definition: Preamble.cpp:591
llvm::StringRef PathRef
A typedef to represent a ref to file path.
Definition: Path.h:29
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
The captured AST context.
Definition: Preamble.h:56
CapturedASTCtx & operator=(CapturedASTCtx &&)=default
CapturedASTCtx & operator=(const CapturedASTCtx &)=delete
CapturedASTCtx(const CapturedASTCtx &)=delete
void setStatCache(std::shared_ptr< PreambleFileStatusCache > StatCache)
Definition: Preamble.h:74
CapturedASTCtx(CompilerInstance &Clang)
Definition: Preamble.h:58
CapturedASTCtx(CapturedASTCtx &&)=default
CompilerInvocation & getCompilerInvocation()
Definition: Preamble.h:72
Preprocessor & getPreprocessor()
Definition: Preamble.h:71
FileManager & getFileManager()
Definition: Preamble.h:73
ASTContext & getASTContext()
Definition: Preamble.h:70
Information required to run clang, e.g. to parse AST or do code completion.
Definition: Compiler.h:48
Timings and statistics from the premble build.
Definition: Preamble.h:128
double FileSystemTime
Time spent in filesystem operations during the build, in seconds.
Definition: Preamble.h:132
size_t BuildSize
Estimate of the memory used while building the preamble.
Definition: Preamble.h:137
double TotalBuildTime
Total wall time it took to build preamble, in seconds.
Definition: Preamble.h:130
size_t SerializedSize
The serialized size of the preamble.
Definition: Preamble.h:140
The parsed preamble and associated data.
Definition: Preamble.h:94
std::vector< Diag > Diags
Definition: Preamble.h:101
std::vector< PragmaMark > Marks
Definition: Preamble.h:112
PrecompiledPreamble Preamble
Definition: Preamble.h:100
std::shared_ptr< const include_cleaner::PragmaIncludes > Pragmas
Definition: Preamble.h:106
PreambleData(PrecompiledPreamble Preamble)
Definition: Preamble.h:95
std::shared_ptr< PreambleFileStatusCache > StatCache
Definition: Preamble.h:115
tooling::CompileCommand CompileCommand
Definition: Preamble.h:99
IncludeStructure Includes
Definition: Preamble.h:104
MainFileMacros Macros
Definition: Preamble.h:110