[clang][deps] NFC: Remove redundant CompilerInstance reference

[jansvoboda11]

Summary

The ModuleDepCollectorPP class holds a reference to ModuleDepCollector as well as ModuleDepCollector's CompilerInstance. The fact that these refer to the same object is non-obvious.

This patch removes the CompilerInvocation reference from ModuleDepCollectorPP and accesses it through ModuleDepCollector instead.

[dexonsmith]

LGTM.

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

 class ModuleDepCollector;
 
 /// Callback that records textual includes and direct modular includes/imports
 /// during preprocessing. At the end of the main file, it also collects
 /// transitive modular dependencies and passes everything to the
 /// \c DependencyConsumer of the parent \c ModuleDepCollector.
 class ModuleDepCollectorPP final : public PPCallbacks {
 public:
-  ModuleDepCollectorPP(CompilerInstance &I, ModuleDepCollector &MDC)
-      : Instance(I), MDC(MDC) {}
+  ModuleDepCollectorPP(ModuleDepCollector &MDC) : MDC(MDC) {}
 
   void FileChanged(SourceLocation Loc, FileChangeReason Reason,
                    SrcMgr::CharacteristicKind FileType,
                    FileID PrevFID) override;
   void InclusionDirective(SourceLocation HashLoc, const Token &IncludeTok,
                           StringRef FileName, bool IsAngled,
                           CharSourceRange FilenameRange, const FileEntry *File,
                           StringRef SearchPath, StringRef RelativePath,
                           const Module *Imported,
                           SrcMgr::CharacteristicKind FileType) override;
   void moduleImport(SourceLocation ImportLoc, ModuleIdPath Path,
                     const Module *Imported) override;
 
   void EndOfMainFile() override;
 
 private:
-  /// The compiler instance for the current translation unit.
-  CompilerInstance &Instance;
   /// The parent dependency collector.
   ModuleDepCollector &MDC;
   /// Working set of direct modular dependencies.
   llvm::DenseSet<const Module *> DirectModularDeps;
   /// Working set of direct modular dependencies that have already been built.
   llvm::DenseSet<const Module *> DirectPrebuiltModularDeps;
 
   void handleImport(const Module *Imported);

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

void ModuleDepCollectorPP::FileChanged(SourceLocation Loc,
                                        SrcMgr::CharacteristicKind FileType,
                                        FileID PrevFID) {
   if (Reason != PPCallbacks::EnterFile)
     return;
   
   // This has to be delayed as the context hash can change at the start of
   // `CompilerInstance::ExecuteAction`.
   if (MDC.ContextHash.empty()) {
-    MDC.ContextHash = Instance.getInvocation().getModuleHash();
+    MDC.ContextHash = MDC.Instance.getInvocation().getModuleHash();
     MDC.Consumer.handleContextHash(MDC.ContextHash);
   }
 
-  SourceManager &SM = Instance.getSourceManager();
+  SourceManager &SM = MDC.Instance.getSourceManager();
 
   // Dependency generation really does want to go all the way to the
   // file entry for a source location to find out what is depended on.
   // We do not want #line markers to affect dependency generation!
   if (Optional<StringRef> Filename =
           SM.getNonBuiltinFilenameForID(SM.getFileID(SM.getExpansionLoc(Loc))))
     MDC.FileDeps.push_back(
         std::string(llvm::sys::path::remove_leading_dotslash(*Filename)));
void ModuleDepCollectorPP::handleImport(const Module *Imported) {
 
   if (MDC.isPrebuiltModule(TopLevelModule))
     DirectPrebuiltModularDeps.insert(TopLevelModule);
   else
     DirectModularDeps.insert(TopLevelModule);
 }
 
 void ModuleDepCollectorPP::EndOfMainFile() {
-  FileID MainFileID = Instance.getSourceManager().getMainFileID();
+  FileID MainFileID = MDC.Instance.getSourceManager().getMainFileID();
   MDC.MainFile = std::string(
-      Instance.getSourceManager().getFileEntryForID(MainFileID)->getName());
+      MDC.Instance.getSourceManager().getFileEntryForID(MainFileID)->getName());
 
-  if (!Instance.getPreprocessorOpts().ImplicitPCHInclude.empty())
-    MDC.FileDeps.push_back(Instance.getPreprocessorOpts().ImplicitPCHInclude);
+  if (!MDC.Instance.getPreprocessorOpts().ImplicitPCHInclude.empty())
+    MDC.FileDeps.push_back(
+        MDC.Instance.getPreprocessorOpts().ImplicitPCHInclude);
 
   for (const Module *M : DirectModularDeps) {
     // A top-level module might not be actually imported as a module when
     // -fmodule-name is used to compile a translation unit that imports this
     // module. In that case it can be skipped. The appropriate header
     // dependencies will still be reported as expected.
     if (!M->getASTFile())
       continue;
ModuleID ModuleDepCollectorPP::handleTopLevelModule(const Module *M) {
 
   ModuleDeps &MD = ModI.first->second;
 
   MD.ID.ModuleName = M->getFullModuleName();
   MD.ImportedByMainFile = DirectModularDeps.contains(M);
   MD.ImplicitModulePCMPath = std::string(M->getASTFile()->getName());
   MD.IsSystem = M->IsSystem;
 
-  const FileEntry *ModuleMap = Instance.getPreprocessor()
+  const FileEntry *ModuleMap = MDC.Instance.getPreprocessor()
                                    .getHeaderSearchInfo()
                                    .getModuleMap()
                                    .getModuleMapFileForUniquing(M);
   MD.ClangModuleMapFile = std::string(ModuleMap ? ModuleMap->getName() : "");
 
   serialization::ModuleFile *MF =
       MDC.Instance.getASTReader()->getModuleManager().lookup(M->getASTFile());
   MDC.Instance.getASTReader()->visitInputFiles(

 
 ModuleDepCollector::ModuleDepCollector(
     std::unique_ptr<DependencyOutputOptions> Opts, CompilerInstance &I,
     DependencyConsumer &C, CompilerInvocation &&OriginalCI, bool OptimizeArgs)
     : Instance(I), Consumer(C), Opts(std::move(Opts)),
       OriginalInvocation(std::move(OriginalCI)), OptimizeArgs(OptimizeArgs) {}
 
 void ModuleDepCollector::attachToPreprocessor(Preprocessor &PP) {
-  PP.addPPCallbacks(std::make_unique<ModuleDepCollectorPP>(Instance, *this));
+  PP.addPPCallbacks(std::make_unique<ModuleDepCollectorPP>(*this));
 }
 
 void ModuleDepCollector::attachToASTReader(ASTReader &R) {}
 
 bool ModuleDepCollector::isPrebuiltModule(const Module *M) {
   std::string Name(M->getTopLevelModuleName());
   const auto &PrebuiltModuleFiles =
       Instance.getHeaderSearchOpts().PrebuiltModuleFiles;
   auto PrebuiltModuleFileIt = PrebuiltModuleFiles.find(Name);
   if (PrebuiltModuleFileIt == PrebuiltModuleFiles.end())
     return false;
   assert("Prebuilt module came from the expected AST file" &&
          PrebuiltModuleFileIt->second == M->getASTFile()->getName());
   return true;
 }