[clang][DependencyScanning] Implementation of CompilerInstanceWithContext to Improve By-Name Queries

clang/include/clang/Frontend/CompilerInstance.h

@@ -946,6 +946,12 @@ class CompilerInstance : public ModuleLoader {
     DependencyCollectors.push_back(std::move(Listener));
   }
 
+  void clearDependencyCollectors() { DependencyCollectors.clear(); }
+
+  std::vector<std::shared_ptr<DependencyCollector>> &getDependencyCollectors() {
+    return DependencyCollectors;
+  }
+
   void setExternalSemaSource(IntrusiveRefCntPtr<ExternalSemaSource> ESS);
 
   ModuleCache &getModuleCache() const { return *ModCache; }

clang/include/clang/Frontend/FrontendActions.h

@@ -320,15 +320,6 @@ class PrintPreprocessedAction : public PreprocessorFrontendAction {
   bool hasPCHSupport() const override { return true; }
 };
 
-class GetDependenciesByModuleNameAction : public PreprocessOnlyAction {
-  StringRef ModuleName;
-  void ExecuteAction() override;
-
-public:
-  GetDependenciesByModuleNameAction(StringRef ModuleName)
-      : ModuleName(ModuleName) {}
-};
-
 //===----------------------------------------------------------------------===//
 // HLSL Specific Actions
 //===----------------------------------------------------------------------===//

clang/include/clang/Frontend/Utils.h

@@ -40,6 +40,7 @@ class DiagnosticsEngine;
 class ExternalSemaSource;
 class FrontendOptions;
 class PCHContainerReader;
+class PPCallbacks;
 class Preprocessor;
 class PreprocessorOptions;
 class PreprocessorOutputOptions;
@@ -87,6 +88,9 @@ class DependencyCollector {
                                   bool IsSystem, bool IsModuleFile,
                                   bool IsMissing);
 
+  /// @return the PPCallback this collector added to the Preprocessor.
+  virtual PPCallbacks *getPPCallbacks() { return nullptr; };
+
 protected:
   /// Return true if the filename was added to the list of dependencies, false
   /// otherwise.

clang/include/clang/Lex/Preprocessor.h

@@ -1327,6 +1327,7 @@ class Preprocessor {
                                                 std::move(Callbacks));
     Callbacks = std::move(C);
   }
+  void removePPCallbacks() { Callbacks.reset(); }
   /// \}
 
   /// Get the number of tokens processed so far.

clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h

@@ -151,14 +151,44 @@ class DependencyScanningTool {
       LookupModuleOutputCallback LookupModuleOutput,
       std::optional<llvm::MemoryBufferRef> TUBuffer = std::nullopt);
 
-  /// Given a compilation context specified via the Clang driver command-line,
-  /// gather modular dependencies of module with the given name, and return the
-  /// information needed for explicit build.
-  llvm::Expected<TranslationUnitDeps> getModuleDependencies(
-      StringRef ModuleName, const std::vector<std::string> &CommandLine,
-      StringRef CWD, const llvm::DenseSet<ModuleID> &AlreadySeen,
+  /// The following three methods provide a new interface to perform
+  /// by name dependency scan. The new interface's intention is to improve
+  /// dependency scanning performance when a sequence of name is looked up
+  /// with the same current working directory and the command line.
+
+  /// @brief Initializing the context and the compiler instance.
+  ///        This method must be called before calling
+  ///        computeDependenciesByNameWithContext.
+  /// @param CWD The current working directory used during the scan.
+  /// @param CommandLine The commandline used for the scan.
+  /// @return Error if the initializaiton fails.
+  llvm::Error initializeCompilerInstanceWithContext(
+      StringRef CWD, const std::vector<std::string> &CommandLine);
+
+  /// @brief Computes the dependeny for the module named ModuleName.
+  /// @param ModuleName The name of the module for which this method computes
+  ///.                  dependencies.
+  /// @param AlreadySeen This stores modules which have previously been
+  ///                    reported. Use the same instance for all calls to this
+  ///                    function for a single \c DependencyScanningTool in a
+  ///                    single build. Note that this parameter is not part of
+  ///                    the context because it can be shared across different
+  ///                    worker threads and each worker thread may update it.
+  /// @param LookupModuleOutput This function is called to fill in
+  ///                           "-fmodule-file=", "-o" and other output
+  ///                           arguments for dependencies.
+  /// @return An instance of \c TranslationUnitDeps if the scan is successful.
+  ///         Otherwise it returns an error.
+  llvm::Expected<TranslationUnitDeps> computeDependenciesByNameWithContext(
+      StringRef ModuleName, const llvm::DenseSet<ModuleID> &AlreadySeen,
       LookupModuleOutputCallback LookupModuleOutput);
 
+  /// @brief This method finializes the compiler instance. It finalizes the
+  ///        diagnostics and deletes the compiler instance. Call this method
+  ///        once all names for a same commandline are scanned.
+  /// @return Error if an error occured during finalization.
+  llvm::Error finalizeCompilerInstanceWithContext();
+
   llvm::vfs::FileSystem &getWorkerVFS() const { return Worker.getVFS(); }
 
 private:

clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h

@@ -29,6 +29,7 @@ namespace tooling {
 namespace dependencies {
 
 class DependencyScanningWorkerFilesystem;
+class CompilerInstanceWithContext;
 
 /// A command-line tool invocation that is part of building a TU.
 ///
@@ -89,6 +90,8 @@ class DependencyScanningWorker {
   DependencyScanningWorker(DependencyScanningService &Service,
                            llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS);
 
+  ~DependencyScanningWorker();
+
   /// Run the dependency scanning tool for a given clang driver command-line,
   /// and report the discovered dependencies to the provided consumer. If
   /// TUBuffer is not nullopt, it is used as TU input for the dependency
@@ -103,18 +106,6 @@ class DependencyScanningWorker {
       DiagnosticConsumer &DiagConsumer,
       std::optional<llvm::MemoryBufferRef> TUBuffer = std::nullopt);
 
-  /// Run the dependency scanning tool for a given clang driver command-line
-  /// for a specific module.
-  ///
-  /// \returns false if clang errors occurred (with diagnostics reported to
-  /// \c DiagConsumer), true otherwise.
-  bool computeDependencies(StringRef WorkingDirectory,
-                           const std::vector<std::string> &CommandLine,
-                           DependencyConsumer &DepConsumer,
-                           DependencyActionController &Controller,
-                           DiagnosticConsumer &DiagConsumer,
-                           StringRef ModuleName);
-
   /// Run the dependency scanning tool for a given clang driver command-line
   /// for a specific translation unit via file system or memory buffer.
   ///
@@ -125,16 +116,33 @@ class DependencyScanningWorker {
       DependencyConsumer &Consumer, DependencyActionController &Controller,
       std::optional<llvm::MemoryBufferRef> TUBuffer = std::nullopt);
 
-  /// Run the dependency scanning tool for a given clang driver command-line
-  /// for a specific module.
-  ///
-  /// \returns A \c StringError with the diagnostic output if clang errors
-  /// occurred, success otherwise.
-  llvm::Error computeDependencies(StringRef WorkingDirectory,
-                                  const std::vector<std::string> &CommandLine,
-                                  DependencyConsumer &Consumer,
-                                  DependencyActionController &Controller,
-                                  StringRef ModuleName);
+  /// The three method below implements a new interface for by name
+  /// dependency scanning. They together enable the dependency scanning worker
+  /// to more effectively perform scanning for a sequence of modules
+  /// by name when the CWD and CommandLine do not change across the queries.
+
+  /// @brief Initializing the context and the compiler instance.
+  /// @param CWD The current working directory used during the scan.
+  /// @param CommandLine The commandline used for the scan.
+  /// @return Error if the initializaiton fails.
+  llvm::Error initializeCompierInstanceWithContext(
+      StringRef CWD, const std::vector<std::string> &CommandLine);
+
+  /// @brief Performaces dependency scanning for the module whose name is
+  ///        specified.
+  /// @param ModuleName  The name of the module whose dependency will be
+  ///                    scanned.
+  /// @param Consumer The dependency consumer that stores the results.
+  /// @param Controller The controller for the dependency scanning action.
+  /// @return Error if the scanner incurs errors.
+  llvm::Error
+  computeDependenciesByNameWithContext(StringRef ModuleName,
+                                       DependencyConsumer &Consumer,
+                                       DependencyActionController &Controller);
+
+  /// @brief Finalizes the diagnostics engine and deletes the compiler instance.
+  /// @return Error if errors occur during finalization.
+  llvm::Error finalizeCompilerInstanceWithContext();
 
   llvm::vfs::FileSystem &getVFS() const { return *BaseFS; }
 
@@ -151,14 +159,16 @@ class DependencyScanningWorker {
   /// (passed in the constructor).
   llvm::IntrusiveRefCntPtr<DependencyScanningWorkerFilesystem> DepFS;
 
+  friend class CompilerInstanceWithContext;
+  std::unique_ptr<CompilerInstanceWithContext> CIWithContext;
+
   /// Private helper functions.
   bool scanDependencies(StringRef WorkingDirectory,
                         const std::vector<std::string> &CommandLine,
                         DependencyConsumer &Consumer,
                         DependencyActionController &Controller,
                         DiagnosticConsumer &DC,
-                        llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
-                        std::optional<StringRef> ModuleName);
+                        llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS);
 };
 
 } // end namespace dependencies

clang/include/clang/Tooling/DependencyScanning/ModuleDepCollector.h

@@ -288,6 +288,8 @@ class ModuleDepCollector final : public DependencyCollector {
   void attachToPreprocessor(Preprocessor &PP) override;
   void attachToASTReader(ASTReader &R) override;
 
+  PPCallbacks *getPPCallbacks() override { return CollectorPPPtr; }
+
   /// Apply any changes implied by the discovered dependencies to the given
   /// invocation, (e.g. disable implicit modules, add explicit module paths).
   void applyDiscoveredDependencies(CompilerInvocation &CI);
@@ -339,6 +341,10 @@ class ModuleDepCollector final : public DependencyCollector {
   std::optional<P1689ModuleInfo> ProvidedStdCXXModule;
   std::vector<P1689ModuleInfo> RequiredStdCXXModules;
 
+  /// A pointer to the preprocessor callback so we can invoke it directly
+  /// if needed.
+  ModuleDepCollectorPP *CollectorPPPtr = nullptr;
+
   /// Checks whether the module is known as being prebuilt.
   bool isPrebuiltModule(const Module *M);
 

clang/lib/Frontend/FrontendActions.cpp

@@ -1233,20 +1233,6 @@ void PrintDependencyDirectivesSourceMinimizerAction::ExecuteAction() {
                                     llvm::outs());
 }
 
-void GetDependenciesByModuleNameAction::ExecuteAction() {
-  CompilerInstance &CI = getCompilerInstance();
-  Preprocessor &PP = CI.getPreprocessor();
-  SourceManager &SM = PP.getSourceManager();
-  FileID MainFileID = SM.getMainFileID();
-  SourceLocation FileStart = SM.getLocForStartOfFile(MainFileID);
-  SmallVector<IdentifierLoc, 2> Path;
-  IdentifierInfo *ModuleID = PP.getIdentifierInfo(ModuleName);
-  Path.emplace_back(FileStart, ModuleID);
-  auto ModResult = CI.loadModule(FileStart, Path, Module::Hidden, false);
-  PPCallbacks *CB = PP.getPPCallbacks();
-  CB->moduleImport(SourceLocation(), Path, ModResult);
-}
-
 //===----------------------------------------------------------------------===//
 // HLSL Specific Actions
 //===----------------------------------------------------------------------===//