[clang][DependencyScanning] Track dependencies from prebuilt modules to

cyndyishida · cyndyishida · commit 3aaaf3371215 · 2025-04-07T10:54:05.000-07:00
determine IsInStableDir

When a module is being scanned, it can depend on modules that have
already been built from a pch dependency. When this happens, the
pcm files are reused for the module dependencies. When this is the case,
check if input files recorded from the PCMs come from the provided stable directories transitively,
since the scanner will not have access to the full set of file dependencies from prebuilt modules.
diff --git a/clang/include/clang/Serialization/ASTReader.h b/clang/include/clang/Serialization/ASTReader.h
@@ -237,6 +237,17 @@ class ASTReaderListener {
     return true;
   }
 
+  /// Overloaded member function of \c visitInputFile that should
+  /// be defined when the input file contains both the virtual and external
+  /// paths, for example when deserializing input files from AST files.
+  ///
+  /// \returns true to continue receiving the next input file, false to stop.
+  virtual bool visitInputFile(StringRef FilenameAsRequested, StringRef Filename,
+                              bool isSystem, bool isOverridden,
+                              bool isExplicitModule) {
+    return true;
+  }
+
   /// Returns true if this \c ASTReaderListener wants to receive the
   /// imports of the AST file via \c visitImport, false otherwise.
   virtual bool needsImportVisitation() const { return false; }
diff --git a/clang/include/clang/Tooling/DependencyScanning/ModuleDepCollector.h b/clang/include/clang/Tooling/DependencyScanning/ModuleDepCollector.h
@@ -33,6 +33,7 @@ namespace dependencies {
 
 class DependencyActionController;
 class DependencyConsumer;
+class PrebuiltModuleASTAttrs;
 
 /// Modular dependency that has already been built prior to the dependency scan.
 struct PrebuiltModuleDep {
@@ -46,6 +47,47 @@ struct PrebuiltModuleDep {
         ModuleMapFile(M->PresumedModuleMapFile) {}
 };
 
+/// Attributes loaded from AST files of prebuilt modules collected prior to
+/// ModuleDepCollector creation.
+using PrebuiltModulesAttrsMap = llvm::StringMap<PrebuiltModuleASTAttrs>;
+class PrebuiltModuleASTAttrs {
+public:
+  /// When a module is discovered to not be in stable directories, traverse &
+  /// update all modules that depend on it.
+  void
+  updateDependentsNotInStableDirs(PrebuiltModulesAttrsMap &PrebuiltModulesMap);
+
+  /// Read-only access to whether the module is made up of dependencies in
+  /// stable directories.
+  bool isInStableDir() const { return IsInStableDirs; }
+
+  /// Read-only access to vfs map files.
+  const llvm::StringSet<> &getVFS() const { return VFSMap; }
+
+  /// Update the VFSMap to the one discovered from serializing the AST file.
+  void setVFS(llvm::StringSet<> &&VFS) { VFSMap = std::move(VFS); }
+
+  /// Add a direct dependent module file, so it can be updated if the current
+  /// module is from stable directores.
+  void addDependent(StringRef ModuleFile) {
+    ModuleFileDependents.insert(ModuleFile);
+  }
+
+  /// Update whether the prebuilt module resolves entirely in a stable
+  /// directories.
+  void setInStableDir(bool V = false) {
+    // Cannot reset attribute once it's false.
+    if (!IsInStableDirs)
+      return;
+    IsInStableDirs = V;
+  }
+
+private:
+  llvm::StringSet<> VFSMap;
+  bool IsInStableDirs = true;
+  std::set<StringRef> ModuleFileDependents;
+};
+
 /// This is used to identify a specific module.
 struct ModuleID {
   /// The name of the module. This may include `:` for C++20 module partitions,
@@ -171,8 +213,6 @@ struct ModuleDeps {
       BuildInfo;
 };
 
-using PrebuiltModuleVFSMapT = llvm::StringMap<llvm::StringSet<>>;
-
 class ModuleDepCollector;
 
 /// Callback that records textual includes and direct modular includes/imports
@@ -242,7 +282,7 @@ class ModuleDepCollector final : public DependencyCollector {
                      CompilerInstance &ScanInstance, DependencyConsumer &C,
                      DependencyActionController &Controller,
                      CompilerInvocation OriginalCI,
-                     PrebuiltModuleVFSMapT PrebuiltModuleVFSMap);
+                     const PrebuiltModulesAttrsMap PrebuiltModulesASTMap);
 
   void attachToPreprocessor(Preprocessor &PP) override;
   void attachToASTReader(ASTReader &R) override;
@@ -262,8 +302,9 @@ class ModuleDepCollector final : public DependencyCollector {
   DependencyConsumer &Consumer;
   /// Callbacks for computing dependency information.
   DependencyActionController &Controller;
-  /// Mapping from prebuilt AST files to their sorted list of VFS overlay files.
-  PrebuiltModuleVFSMapT PrebuiltModuleVFSMap;
+  /// Mapping from prebuilt AST filepaths to their attributes referenced during
+  /// dependency collecting.
+  const PrebuiltModulesAttrsMap PrebuiltModulesASTMap;
   /// Path to the main source file.
   std::string MainFile;
   /// Hash identifying the compilation conditions of the current TU.
@@ -339,6 +380,14 @@ void resetBenignCodeGenOptions(frontend::ActionKind ProgramAction,
 bool isPathInStableDir(const ArrayRef<StringRef> Directories,
                        const StringRef Input);
 
+/// Determine if options collected from a module's
+/// compilation can safely be considered as stable.
+///
+/// \param Directories Paths known to be in a stable location. e.g. Sysroot.
+/// \param HSOpts Header search options derived from the compiler invocation.
+bool areOptionsInStableDir(const ArrayRef<StringRef> Directories,
+                           const HeaderSearchOptions &HSOpts);
+
 } // end namespace dependencies
 } // end namespace tooling
 } // end namespace clang
diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
@@ -777,10 +777,11 @@ namespace {
     /// Indicates that the AST file contains particular input file.
     ///
     /// \returns true to continue receiving the next input file, false to stop.
-    bool visitInputFile(StringRef Filename, bool isSystem,
-                        bool isOverridden, bool isExplicitModule) override {
+    bool visitInputFile(StringRef FilenameAsRequested, StringRef Filename,
+                        bool isSystem, bool isOverridden,
+                        bool isExplicitModule) override {
 
-      Out.indent(2) << "Input file: " << Filename;
+      Out.indent(2) << "Input file: " << FilenameAsRequested;
 
       if (isSystem || isOverridden || isExplicitModule) {
         Out << " [";
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
@@ -5835,9 +5835,13 @@ bool ASTReader::readASTFileControlBlock(
           break;
         case INPUT_FILE:
           bool Overridden = static_cast<bool>(Record[3]);
+          size_t FilenameLen = ModuleDir.size() + Record[7] + 1;
           auto Filename = ResolveImportedPath(PathBuf, Blob, ModuleDir);
+          StringRef FilenameAsRequested = Filename->substr(0, FilenameLen);
+          StringRef ExternalFilename = Filename->substr(FilenameLen);
           shouldContinue = Listener.visitInputFile(
-              *Filename, isSystemFile, Overridden, /*IsExplicitModule=*/false);
+              FilenameAsRequested, ExternalFilename, isSystemFile, Overridden,
+              /*IsExplicitModule=*/false);
           break;
         }
         if (!shouldContinue)
diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
@@ -90,63 +90,135 @@ static bool checkHeaderSearchPaths(const HeaderSearchOptions &HSOpts,
 
 using PrebuiltModuleFilesT = decltype(HeaderSearchOptions::PrebuiltModuleFiles);
 
-/// A listener that collects the imported modules and optionally the input
-/// files.
+/// A listener that collects the imported modules and the input
+/// files. While visiting, collect vfsoverlays and file inputs that determine
+/// whether prebuilt modules fully resolve in stable directories.
 class PrebuiltModuleListener : public ASTReaderListener {
 public:
   PrebuiltModuleListener(PrebuiltModuleFilesT &PrebuiltModuleFiles,
                          llvm::SmallVector<std::string> &NewModuleFiles,
-                         PrebuiltModuleVFSMapT &PrebuiltModuleVFSMap,
+                         PrebuiltModulesAttrsMap &PrebuiltModulesASTMap,
                          const HeaderSearchOptions &HSOpts,
-                         const LangOptions &LangOpts, DiagnosticsEngine &Diags)
+                         const LangOptions &LangOpts, DiagnosticsEngine &Diags,
+                         const llvm::SmallVector<StringRef> &StableDirs)
       : PrebuiltModuleFiles(PrebuiltModuleFiles),
         NewModuleFiles(NewModuleFiles),
-        PrebuiltModuleVFSMap(PrebuiltModuleVFSMap), ExistingHSOpts(HSOpts),
-        ExistingLangOpts(LangOpts), Diags(Diags) {}
+        PrebuiltModulesASTMap(PrebuiltModulesASTMap), ExistingHSOpts(HSOpts),
+        ExistingLangOpts(LangOpts), Diags(Diags), StableDirs(StableDirs) {}
 
   bool needsImportVisitation() const override { return true; }
+  bool needsInputFileVisitation() override { return true; }
+  bool needsSystemInputFileVisitation() override { return true; }
 
+  /// Accumulate the modules are transitively depended on by the initial
+  /// prebuilt module.
   void visitImport(StringRef ModuleName, StringRef Filename) override {
     if (PrebuiltModuleFiles.insert({ModuleName.str(), Filename.str()}).second)
       NewModuleFiles.push_back(Filename.str());
+
+    if (PrebuiltModulesASTMap.try_emplace(Filename).second)
+      PrebuiltModulesASTMap[Filename].setInStableDir(!StableDirs.empty());
+
+    if (auto It = PrebuiltModulesASTMap.find(CurrentFile);
+        It != PrebuiltModulesASTMap.end() && CurrentFile != Filename)
+      PrebuiltModulesASTMap[Filename].addDependent(It->getKey());
+  }
+
+  /// For each input file discovered, check whether it's external path is in a
+  /// stable directory. Traversal is stopped if the current module is not
+  /// considered stable.
+  bool visitInputFile(StringRef FilenameAsRequested, StringRef ExternalFilename,
+                      bool isSystem, bool isOverridden,
+                      bool isExplicitModule) override {
+    if (StableDirs.empty())
+      return false;
+    if (!PrebuiltModulesASTMap.contains(CurrentFile) ||
+        !PrebuiltModulesASTMap[CurrentFile].isInStableDir())
+      return false;
+
+    const StringRef FileToUse =
+        ExternalFilename.empty() ? FilenameAsRequested : ExternalFilename;
+
+    PrebuiltModulesASTMap[CurrentFile].setInStableDir(
+        isPathInStableDir(StableDirs, FileToUse));
+    return PrebuiltModulesASTMap[CurrentFile].isInStableDir();
   }
 
+  /// Update which module that is being actively traversed.
   void visitModuleFile(StringRef Filename,
                        serialization::ModuleKind Kind) override {
+    // If the CurrentFile is not
+    // considered stable, update any of it's transitive dependents.
+    if (PrebuiltModulesASTMap.contains(CurrentFile) &&
+        !PrebuiltModulesASTMap[CurrentFile].isInStableDir())
+      PrebuiltModulesASTMap[CurrentFile].updateDependentsNotInStableDirs(
+          PrebuiltModulesASTMap);
     CurrentFile = Filename;
   }
 
+  /// Check the header search options for a given module when considering
+  /// if the module comes from stable directories.
+  bool ReadHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
+                               StringRef ModuleFilename,
+                               StringRef SpecificModuleCachePath,
+                               bool Complain) override {
+    if (PrebuiltModulesASTMap.try_emplace(CurrentFile).second)
+      PrebuiltModulesASTMap[CurrentFile].setInStableDir(!StableDirs.empty());
+
+    if (PrebuiltModulesASTMap[CurrentFile].isInStableDir())
+      PrebuiltModulesASTMap[CurrentFile].setInStableDir(
+          areOptionsInStableDir(StableDirs, HSOpts));
+
+    return false;
+  }
+
+  /// Accumulate vfsoverlays used to build these prebuilt modules.
   bool ReadHeaderSearchPaths(const HeaderSearchOptions &HSOpts,
                              bool Complain) override {
-    std::vector<std::string> VFSOverlayFiles = HSOpts.VFSOverlayFiles;
-    PrebuiltModuleVFSMap.try_emplace(CurrentFile, llvm::from_range,
-                                     VFSOverlayFiles);
+
+    if (PrebuiltModulesASTMap.try_emplace(CurrentFile).second)
+      PrebuiltModulesASTMap[CurrentFile].setInStableDir(!StableDirs.empty());
+
+    PrebuiltModulesASTMap[CurrentFile].setVFS(
+        llvm::StringSet<>(llvm::from_range, HSOpts.VFSOverlayFiles));
+
     return checkHeaderSearchPaths(
         HSOpts, ExistingHSOpts, Complain ? &Diags : nullptr, ExistingLangOpts);
   }
 
 private:
   PrebuiltModuleFilesT &PrebuiltModuleFiles;
   llvm::SmallVector<std::string> &NewModuleFiles;
-  PrebuiltModuleVFSMapT &PrebuiltModuleVFSMap;
+  PrebuiltModulesAttrsMap &PrebuiltModulesASTMap;
   const HeaderSearchOptions &ExistingHSOpts;
   const LangOptions &ExistingLangOpts;
   DiagnosticsEngine &Diags;
   std::string CurrentFile;
+  const llvm::SmallVector<StringRef> &StableDirs;
 };
 
 /// Visit the given prebuilt module and collect all of the modules it
 /// transitively imports and contributing input files.
 static bool visitPrebuiltModule(StringRef PrebuiltModuleFilename,
                                 CompilerInstance &CI,
                                 PrebuiltModuleFilesT &ModuleFiles,
-                                PrebuiltModuleVFSMapT &PrebuiltModuleVFSMap,
+                                PrebuiltModulesAttrsMap &PrebuiltModulesASTMap,
                                 DiagnosticsEngine &Diags) {
+
+  // Gather the set of stable directories to use as transitive dependencies are
+  // discovered.
+  llvm::SmallVector<StringRef> StableDirs;
+  std::string SysrootToUse(CI.getHeaderSearchOpts().Sysroot);
+  if (!SysrootToUse.empty() &&
+      (llvm::sys::path::root_directory(SysrootToUse) != SysrootToUse))
+    StableDirs = {SysrootToUse, CI.getHeaderSearchOpts().ResourceDir};
+
   // List of module files to be processed.
   llvm::SmallVector<std::string> Worklist;
-  PrebuiltModuleListener Listener(ModuleFiles, Worklist, PrebuiltModuleVFSMap,
+
+  PrebuiltModuleListener Listener(ModuleFiles, Worklist, PrebuiltModulesASTMap,
                                   CI.getHeaderSearchOpts(), CI.getLangOpts(),
-                                  Diags);
+                                  Diags, StableDirs);
 
   Listener.visitModuleFile(PrebuiltModuleFilename,
                            serialization::MK_ExplicitModule);
@@ -371,16 +443,18 @@ class DependencyScanningAction : public tooling::ToolAction {
     auto *FileMgr = ScanInstance.createFileManager(FS);
     ScanInstance.createSourceManager(*FileMgr);
 
-    // Store the list of prebuilt module files into header search options. This
-    // will prevent the implicit build to create duplicate modules and will
-    // force reuse of the existing prebuilt module files instead.
-    PrebuiltModuleVFSMapT PrebuiltModuleVFSMap;
+    // Store a mapping of prebuilt module files and their properties like header
+    // search options. This will prevent the implicit build to create duplicate
+    // modules and will force reuse of the existing prebuilt module files
+    // instead.
+    PrebuiltModulesAttrsMap PrebuiltModulesASTMap;
+
     if (!ScanInstance.getPreprocessorOpts().ImplicitPCHInclude.empty())
       if (visitPrebuiltModule(
               ScanInstance.getPreprocessorOpts().ImplicitPCHInclude,
               ScanInstance,
               ScanInstance.getHeaderSearchOpts().PrebuiltModuleFiles,
-              PrebuiltModuleVFSMap, ScanInstance.getDiagnostics()))
+              PrebuiltModulesASTMap, ScanInstance.getDiagnostics()))
         return false;
 
     // Create the dependency collector that will collect the produced
@@ -410,7 +484,7 @@ class DependencyScanningAction : public tooling::ToolAction {
     case ScanningOutputFormat::Full:
       MDC = std::make_shared<ModuleDepCollector>(
           Service, std::move(Opts), ScanInstance, Consumer, Controller,
-          OriginalInvocation, std::move(PrebuiltModuleVFSMap));
+          OriginalInvocation, std::move(PrebuiltModulesASTMap));
       ScanInstance.addDependencyCollector(MDC);
       break;
     }
diff --git a/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp b/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
diff --git a/clang/test/ClangScanDeps/prebuilt-modules-in-stable-dirs.c b/clang/test/ClangScanDeps/prebuilt-modules-in-stable-dirs.c
