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PrecompiledPreamble.h
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1 //===--- PrecompiledPreamble.h - Build precompiled preambles ----*- 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 // Helper class to build precompiled preamble.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_FRONTEND_PRECOMPILED_PREAMBLE_H
15 #define LLVM_CLANG_FRONTEND_PRECOMPILED_PREAMBLE_H
16 
17 #include "clang/Lex/Lexer.h"
18 #include "clang/Lex/Preprocessor.h"
19 #include "llvm/ADT/IntrusiveRefCntPtr.h"
20 #include "llvm/Support/AlignOf.h"
21 #include "llvm/Support/MD5.h"
22 #include <cstddef>
23 #include <memory>
24 #include <system_error>
25 #include <type_traits>
26 
27 namespace llvm {
28 class MemoryBuffer;
29 }
30 
31 namespace clang {
32 namespace vfs {
33 class FileSystem;
34 }
35 
36 class CompilerInstance;
37 class CompilerInvocation;
38 class DeclGroupRef;
39 class PCHContainerOperations;
40 
41 /// Runs lexer to compute suggested preamble bounds.
42 PreambleBounds ComputePreambleBounds(const LangOptions &LangOpts,
43  llvm::MemoryBuffer *Buffer,
44  unsigned MaxLines);
45 
46 class PreambleCallbacks;
47 
48 /// A class holding a PCH and all information to check whether it is valid to
49 /// reuse the PCH for the subsequent runs. Use BuildPreamble to create PCH and
50 /// CanReusePreamble + AddImplicitPreamble to make use of it.
52  class PCHStorage;
53  struct PreambleFileHash;
54 
55 public:
56  /// Try to build PrecompiledPreamble for \p Invocation. See
57  /// BuildPreambleError for possible error codes.
58  ///
59  /// \param Invocation Original CompilerInvocation with options to compile the
60  /// file.
61  ///
62  /// \param MainFileBuffer Buffer with the contents of the main file.
63  ///
64  /// \param Bounds Bounds of the preamble, result of calling
65  /// ComputePreambleBounds.
66  ///
67  /// \param Diagnostics Diagnostics engine to be used while building the
68  /// preamble.
69  ///
70  /// \param VFS An instance of vfs::FileSystem to be used for file
71  /// accesses.
72  ///
73  /// \param PCHContainerOps An instance of PCHContainerOperations.
74  ///
75  /// \param StoreInMemory Store PCH in memory. If false, PCH will be stored in
76  /// a temporary file.
77  ///
78  /// \param Callbacks A set of callbacks to be executed when building
79  /// the preamble.
80  static llvm::ErrorOr<PrecompiledPreamble>
81  Build(const CompilerInvocation &Invocation,
82  const llvm::MemoryBuffer *MainFileBuffer, PreambleBounds Bounds,
84  std::shared_ptr<PCHContainerOperations> PCHContainerOps,
85  bool StoreInMemory, PreambleCallbacks &Callbacks);
86 
88  PrecompiledPreamble &operator=(PrecompiledPreamble &&) = default;
89 
90  /// PreambleBounds used to build the preamble.
91  PreambleBounds getBounds() const;
92 
93  /// Returns the size, in bytes, that preamble takes on disk or in memory.
94  /// For on-disk preambles returns 0 if filesystem operations fail. Intended to
95  /// be used for logging and debugging purposes only.
96  std::size_t getSize() const;
97 
98  /// Check whether PrecompiledPreamble can be reused for the new contents(\p
99  /// MainFileBuffer) of the main file.
100  bool CanReuse(const CompilerInvocation &Invocation,
101  const llvm::MemoryBuffer *MainFileBuffer, PreambleBounds Bounds,
102  vfs::FileSystem *VFS) const;
103 
104  /// Changes options inside \p CI to use PCH from this preamble. Also remaps
105  /// main file to \p MainFileBuffer and updates \p VFS to ensure the preamble
106  /// is accessible.
107  /// Requires that CanReuse() is true.
108  /// For in-memory preambles, PrecompiledPreamble instance continues to own the
109  /// MemoryBuffer with the Preamble after this method returns. The caller is
110  /// responsible for making sure the PrecompiledPreamble instance outlives the
111  /// compiler run and the AST that will be using the PCH.
112  void AddImplicitPreamble(CompilerInvocation &CI,
114  llvm::MemoryBuffer *MainFileBuffer) const;
115 
116  /// Configure \p CI to use this preamble.
117  /// Like AddImplicitPreamble, but doesn't assume CanReuse() is true.
118  /// If this preamble does not match the file, it may parse differently.
119  void OverridePreamble(CompilerInvocation &CI,
121  llvm::MemoryBuffer *MainFileBuffer) const;
122 
123 private:
124  PrecompiledPreamble(PCHStorage Storage, std::vector<char> PreambleBytes,
125  bool PreambleEndsAtStartOfLine,
126  llvm::StringMap<PreambleFileHash> FilesInPreamble);
127 
128  /// A temp file that would be deleted on destructor call. If destructor is not
129  /// called for any reason, the file will be deleted at static objects'
130  /// destruction.
131  /// An assertion will fire if two TempPCHFiles are created with the same name,
132  /// so it's not intended to be used outside preamble-handling.
133  class TempPCHFile {
134  public:
135  // A main method used to construct TempPCHFile.
136  static llvm::ErrorOr<TempPCHFile> CreateNewPreamblePCHFile();
137 
138  /// Call llvm::sys::fs::createTemporaryFile to create a new temporary file.
139  static llvm::ErrorOr<TempPCHFile> createInSystemTempDir(const Twine &Prefix,
140  StringRef Suffix);
141  /// Create a new instance of TemporaryFile for file at \p Path. Use with
142  /// extreme caution, there's an assertion checking that there's only a
143  /// single instance of TempPCHFile alive for each path.
144  static llvm::ErrorOr<TempPCHFile> createFromCustomPath(const Twine &Path);
145 
146  private:
147  TempPCHFile(std::string FilePath);
148 
149  public:
150  TempPCHFile(TempPCHFile &&Other);
151  TempPCHFile &operator=(TempPCHFile &&Other);
152 
153  TempPCHFile(const TempPCHFile &) = delete;
154  ~TempPCHFile();
155 
156  /// A path where temporary file is stored.
157  llvm::StringRef getFilePath() const;
158 
159  private:
160  void RemoveFileIfPresent();
161 
162  private:
164  };
165 
166  class InMemoryPreamble {
167  public:
168  std::string Data;
169  };
170 
171  class PCHStorage {
172  public:
173  enum class Kind { Empty, InMemory, TempFile };
174 
175  PCHStorage() = default;
176  PCHStorage(TempPCHFile File);
177  PCHStorage(InMemoryPreamble Memory);
178 
179  PCHStorage(const PCHStorage &) = delete;
180  PCHStorage &operator=(const PCHStorage &) = delete;
181 
182  PCHStorage(PCHStorage &&Other);
183  PCHStorage &operator=(PCHStorage &&Other);
184 
185  ~PCHStorage();
186 
187  Kind getKind() const;
188 
189  TempPCHFile &asFile();
190  const TempPCHFile &asFile() const;
191 
192  InMemoryPreamble &asMemory();
193  const InMemoryPreamble &asMemory() const;
194 
195  private:
196  void destroy();
197  void setEmpty();
198 
199  private:
200  Kind StorageKind = Kind::Empty;
201  llvm::AlignedCharArrayUnion<TempPCHFile, InMemoryPreamble> Storage = {};
202  };
203 
204  /// Data used to determine if a file used in the preamble has been changed.
205  struct PreambleFileHash {
206  /// All files have size set.
207  off_t Size = 0;
208 
209  /// Modification time is set for files that are on disk. For memory
210  /// buffers it is zero.
211  time_t ModTime = 0;
212 
213  /// Memory buffers have MD5 instead of modification time. We don't
214  /// compute MD5 for on-disk files because we hope that modification time is
215  /// enough to tell if the file was changed.
216  llvm::MD5::MD5Result MD5 = {};
217 
218  static PreambleFileHash createForFile(off_t Size, time_t ModTime);
219  static PreambleFileHash
220  createForMemoryBuffer(const llvm::MemoryBuffer *Buffer);
221 
222  friend bool operator==(const PreambleFileHash &LHS,
223  const PreambleFileHash &RHS) {
224  return LHS.Size == RHS.Size && LHS.ModTime == RHS.ModTime &&
225  LHS.MD5 == RHS.MD5;
226  }
227  friend bool operator!=(const PreambleFileHash &LHS,
228  const PreambleFileHash &RHS) {
229  return !(LHS == RHS);
230  }
231  };
232 
233  /// Helper function to set up PCH for the preamble into \p CI and \p VFS to
234  /// with the specified \p Bounds.
235  void configurePreamble(PreambleBounds Bounds, CompilerInvocation &CI,
237  llvm::MemoryBuffer *MainFileBuffer) const;
238 
239  /// Sets up the PreprocessorOptions and changes VFS, so that PCH stored in \p
240  /// Storage is accessible to clang. This method is an implementation detail of
241  /// AddImplicitPreamble.
242  static void setupPreambleStorage(const PCHStorage &Storage,
243  PreprocessorOptions &PreprocessorOpts,
245 
246  /// Manages the memory buffer or temporary file that stores the PCH.
247  PCHStorage Storage;
248  /// Keeps track of the files that were used when computing the
249  /// preamble, with both their buffer size and their modification time.
250  ///
251  /// If any of the files have changed from one compile to the next,
252  /// the preamble must be thrown away.
253  llvm::StringMap<PreambleFileHash> FilesInPreamble;
254  /// The contents of the file that was used to precompile the preamble. Only
255  /// contains first PreambleBounds::Size bytes. Used to compare if the relevant
256  /// part of the file has not changed, so that preamble can be reused.
257  std::vector<char> PreambleBytes;
258  /// See PreambleBounds::PreambleEndsAtStartOfLine
259  bool PreambleEndsAtStartOfLine;
260 };
261 
262 /// A set of callbacks to gather useful information while building a preamble.
264 public:
265  virtual ~PreambleCallbacks() = default;
266 
267  /// Called before FrontendAction::BeginSourceFile.
268  /// Can be used to store references to various CompilerInstance fields
269  /// (e.g. SourceManager) that may be interesting to the consumers of other
270  /// callbacks.
271  virtual void BeforeExecute(CompilerInstance &CI);
272  /// Called after FrontendAction::Execute(), but before
273  /// FrontendAction::EndSourceFile(). Can be used to transfer ownership of
274  /// various CompilerInstance fields before they are destroyed.
275  virtual void AfterExecute(CompilerInstance &CI);
276  /// Called after PCH has been emitted. \p Writer may be used to retrieve
277  /// information about AST, serialized in PCH.
278  virtual void AfterPCHEmitted(ASTWriter &Writer);
279  /// Called for each TopLevelDecl.
280  /// NOTE: To allow more flexibility a custom ASTConsumer could probably be
281  /// used instead, but having only this method allows a simpler API.
282  virtual void HandleTopLevelDecl(DeclGroupRef DG);
283  /// Creates wrapper class for PPCallbacks so we can also process information
284  /// about includes that are inside of a preamble
285  virtual std::unique_ptr<PPCallbacks> createPPCallbacks();
286 };
287 
288 enum class BuildPreambleError {
293 };
294 
295 class BuildPreambleErrorCategory final : public std::error_category {
296 public:
297  const char *name() const noexcept override;
298  std::string message(int condition) const override;
299 };
300 
301 std::error_code make_error_code(BuildPreambleError Error);
302 } // namespace clang
303 
304 namespace std {
305 template <>
306 struct is_error_code_enum<clang::BuildPreambleError> : std::true_type {};
307 } // namespace std
308 
309 #endif
Describes the bounds (start, size) of the preamble and a flag required by PreprocessorOptions::Precom...
Definition: Lexer.h:59
bool operator==(CanQual< T > x, CanQual< U > y)
__SIZE_TYPE__ size_t
The unsigned integer type of the result of the sizeof operator.
Definition: opencl-c.h:60
DominatorTree GraphTraits specialization so the DominatorTree can be iterable by generic graph iterat...
Definition: Dominators.h:30
PreprocessorOptions - This class is used for passing the various options used in preprocessor initial...
The virtual file system interface.
Definition: Format.h:2031
std::error_code make_error_code(BuildPreambleError Error)
Concrete class used by the front-end to report problems and issues.
Definition: Diagnostic.h:149
A set of callbacks to gather useful information while building a preamble.
Defines the clang::Preprocessor interface.
PreambleBounds ComputePreambleBounds(const LangOptions &LangOpts, llvm::MemoryBuffer *Buffer, unsigned MaxLines)
Runs lexer to compute suggested preamble bounds.
Kind
CompilerInstance - Helper class for managing a single instance of the Clang compiler.
Dataflow Directional Tag Classes.
A class holding a PCH and all information to check whether it is valid to reuse the PCH for the subse...
Helper class for holding the data necessary to invoke the compiler.
bool operator!=(CanQual< T > x, CanQual< U > y)
Writes an AST file containing the contents of a translation unit.
Definition: ASTWriter.h:103
static Decl::Kind getKind(const Decl *D)
Definition: DeclBase.cpp:930