[clang][deps] NFC: Report modules' context hash

[jansvoboda11]

Summary

This patch eagerly constructs and modifies CompilerInvocation of modular dependencies in order to report the correct context hash instead of the hash of the original translation unit.

No functionality change here, since we currently don't modify CompilerInvocation in a way that affects the context hash.

Depends on D102473.

[dexonsmith]

LGTM, although I'd slightly prefer the change to CompilerInstance.h be split out and committed after.

clang/include/clang/Frontend/CompilerInstance.h

230–232 ↗

(On Diff #345402)

It'd be nice to remove this API separately in a follow up patch; the change to CompilerInstance.h is not necessary here so it's easy to split, focusing the patch on the relevant changes, and that pattern is easier for reverting (especially in out-of-tree code).

[jansvoboda11]

Thanks for the review!

clang/include/clang/Frontend/CompilerInstance.h

230–232 ↗

(On Diff #345402)

Committed separately as d9cb70ba29dbd74aac294caad0686f1ed52295f9.

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

struct ModuleDeps {
   /// This may include modules with a different context hash when it can be
   /// determined that the differences are benign for this compilation.
   std::vector<ModuleID> ClangModuleDeps;
 
   // Used to track which modules that were discovered were directly imported by
   // the primary TU.
   bool ImportedByMainFile = false;
 
-  /// The compiler invocation associated with the translation unit that imports
-  /// this module.
-  std::shared_ptr<CompilerInvocation> Invocation;
+  /// Compiler invocation that can be used to build this module (without paths).
+  CompilerInvocation Invocation;
 
   /// Gets the canonical command line suitable for passing to clang.
   ///
   /// \param LookupPCMPath This function is called to fill in "-fmodule-file="
   ///                      arguments and the "-o" argument. It needs to return
   ///                      a path for where the PCM for the given module is to
   ///                      be located.
   /// \param LookupModuleDeps This function is called to collect the full

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

 #include "clang/Tooling/DependencyScanning/DependencyScanningWorker.h"
 #include "llvm/Support/StringSaver.h"
 
 using namespace clang;
 using namespace tooling;
 using namespace dependencies;
 
 static CompilerInvocation
-makeInvocationForModuleBuildWithoutPaths(const ModuleDeps &Deps) {
+makeInvocationForModuleBuildWithoutPaths(const ModuleDeps &Deps,
+                                         const CompilerInvocation &Invocation) {
   // Make a deep copy of the invocation.
-  CompilerInvocation CI(*Deps.Invocation);
+  CompilerInvocation CI(Invocation);
 
   // Remove options incompatible with explicit module build.
   CI.getFrontendOpts().Inputs.clear();
   CI.getFrontendOpts().OutputFile.clear();
 
   CI.getFrontendOpts().ProgramAction = frontend::GenerateModule;
   CI.getLangOpts()->ModuleName = Deps.ID.ModuleName;
   CI.getFrontendOpts().IsSystemModule = Deps.IsSystem;
 
   CI.getLangOpts()->ImplicitModules = false;
   CI.getHeaderSearchOpts().ImplicitModuleMaps = false;
 
   return CI;
 }
 
 static std::vector<std::string>
-serializeCompilerInvocation(CompilerInvocation &CI) {
+serializeCompilerInvocation(const CompilerInvocation &CI) {
   // Set up string allocator.
   llvm::BumpPtrAllocator Alloc;
   llvm::StringSaver Strings(Alloc);
   auto SA = [&Strings](const Twine &Arg) { return Strings.save(Arg).data(); };
 
   // Synthesize full command line from the CompilerInvocation, including "-cc1".
   SmallVector<const char *, 32> Args{"-cc1"};
   CI.generateCC1CommandLine(Args, SA);
 
   // Convert arguments to the return type.
   return std::vector<std::string>{Args.begin(), Args.end()};
 }
 
 std::vector<std::string> ModuleDeps::getCanonicalCommandLine(
     std::function<StringRef(ModuleID)> LookupPCMPath,
     std::function<const ModuleDeps &(ModuleID)> LookupModuleDeps) const {
-  CompilerInvocation CI(makeInvocationForModuleBuildWithoutPaths(*this));
+  CompilerInvocation CI(Invocation);
 
   dependencies::detail::collectPCMAndModuleMapPaths(
       ClangModuleDeps, LookupPCMPath, LookupModuleDeps,
       CI.getFrontendOpts().ModuleFiles, CI.getFrontendOpts().ModuleMapFiles);
 
   return serializeCompilerInvocation(CI);
 }
 
 std::vector<std::string>
 ModuleDeps::getCanonicalCommandLineWithoutModulePaths() const {
-  CompilerInvocation CI(makeInvocationForModuleBuildWithoutPaths(*this));
-
-  return serializeCompilerInvocation(CI);
+  return serializeCompilerInvocation(Invocation);
 }
 
 void dependencies::detail::collectPCMAndModuleMapPaths(
     llvm::ArrayRef<ModuleID> Modules,
     std::function<StringRef(ModuleID)> LookupPCMPath,
     std::function<const ModuleDeps &(ModuleID)> LookupModuleDeps,
     std::vector<std::string> &PCMPaths, std::vector<std::string> &ModMapPaths) {
   llvm::StringSet<> AlreadyAdded;
ModuleID ModuleDepCollectorPP::handleTopLevelModule(const Module *M) {
 
   serialization::ModuleFile *MF =
       MDC.Instance.getASTReader()->getModuleManager().lookup(M->getASTFile());
   MDC.Instance.getASTReader()->visitInputFiles(
       *MF, true, true, [&](const serialization::InputFile &IF, bool isSystem) {
         MD.FileDeps.insert(IF.getFile()->getName());
       });
 
-  // FIXME: Prepare the CompilerInvocation for building this module **now**, so
-  //        that we store the actual context hash for this module (not just the
-  //        context hash inherited from the original TU).
-  MD.Invocation = Instance.getInvocationPtr();
-  MD.ID.ContextHash = MD.Invocation->getModuleHash();
+  MD.Invocation =
+      makeInvocationForModuleBuildWithoutPaths(MD, Instance.getInvocation());
+  MD.ID.ContextHash = MD.Invocation.getModuleHash();
 
   llvm::DenseSet<const Module *> AddedModules;
   addAllSubmoduleDeps(M, MD, AddedModules);
 
   return MD.ID;
 }
 
 void ModuleDepCollectorPP::addAllSubmoduleDeps(