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

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.

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D111724

Author: jansvoboda11

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

@@ -147,8 +147,7 @@ class ModuleDepCollector;
 /// \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,
@@ -165,8 +164,6 @@ class ModuleDepCollectorPP final : public PPCallbacks {
   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.

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

@@ -155,12 +155,12 @@ void ModuleDepCollectorPP::FileChanged(SourceLocation Loc,
   // 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(Instance.getDiagnostics());
+    MDC.ContextHash = MDC.Instance.getInvocation().getModuleHash(
+        MDC.Instance.getDiagnostics());
     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.
@@ -203,12 +203,13 @@ void ModuleDepCollectorPP::handleImport(const Module *Imported) {
 }
 
 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
@@ -247,7 +248,7 @@ ModuleID ModuleDepCollectorPP::handleTopLevelModule(const Module *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);
@@ -337,7 +338,7 @@ ModuleDepCollector::ModuleDepCollector(
       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) {}