Index: clang/include/clang/Frontend/CompilerInvocation.h
===================================================================
--- clang/include/clang/Frontend/CompilerInvocation.h
+++ clang/include/clang/Frontend/CompilerInvocation.h
@@ -224,7 +224,7 @@
   std::string getModuleHash() const;
 
   using StringAllocator = llvm::function_ref<const char *(const llvm::Twine &)>;
-  /// Generate a cc1-compatible command line arguments from this instance.
+  /// Generate cc1-compatible command line arguments from this instance.
   ///
   /// \param [out] Args - The generated arguments. Note that the caller is
   /// responsible for inserting the path to the clang executable and "-cc1" if
@@ -235,6 +235,20 @@
   void generateCC1CommandLine(llvm::SmallVectorImpl<const char *> &Args,
                               StringAllocator SA) const;
 
+  /// Generate cc1-compatible command line arguments from this instance,
+  /// wrapping the result as a std::vector<std::string>.
+  ///
+  /// This is a (less-efficient) wrapper over generateCC1CommandLine().
+  std::vector<std::string> getCC1CommandLine() const;
+
+  /// Reset all of the options that are not considered when building a
+  /// module.
+  void resetNonModularOptions();
+
+  /// Disable implicit modules and canonicalize options that are only used by
+  /// implicit modules.
+  void clearImplicitModuleBuildOptions();
+
 private:
   static bool CreateFromArgsImpl(CompilerInvocation &Res,
                                  ArrayRef<const char *> CommandLineArgs,
Index: clang/lib/Frontend/CompilerInstance.cpp
===================================================================
--- clang/lib/Frontend/CompilerInstance.cpp
+++ clang/lib/Frontend/CompilerInstance.cpp
@@ -1150,8 +1150,7 @@
 
   // For any options that aren't intended to affect how a module is built,
   // reset them to their default values.
-  Invocation->getLangOpts()->resetNonModularOptions();
-  PPOpts.resetNonModularOptions();
+  Invocation->resetNonModularOptions();
 
   // Remove any macro definitions that are explicitly ignored by the module.
   // They aren't supposed to affect how the module is built anyway.
Index: clang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- clang/lib/Frontend/CompilerInvocation.cpp
+++ clang/lib/Frontend/CompilerInvocation.cpp
@@ -4672,6 +4672,37 @@
   GenerateDependencyOutputArgs(DependencyOutputOpts, Args, SA);
 }
 
+std::vector<std::string> CompilerInvocation::getCC1CommandLine() const {
+  // 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"};
+  generateCC1CommandLine(Args, SA);
+
+  // Convert arguments to the return type.
+  return std::vector<std::string>{Args.begin(), Args.end()};
+}
+
+void CompilerInvocation::resetNonModularOptions() {
+  getLangOpts()->resetNonModularOptions();
+  getPreprocessorOpts().resetNonModularOptions();
+}
+
+void CompilerInvocation::clearImplicitModuleBuildOptions() {
+  getLangOpts()->ImplicitModules = false;
+  getHeaderSearchOpts().ImplicitModuleMaps = false;
+  getHeaderSearchOpts().ModuleCachePath.clear();
+  getHeaderSearchOpts().ModulesValidateOncePerBuildSession = false;
+  getHeaderSearchOpts().BuildSessionTimestamp = 0;
+  // The specific values we canonicalize to for pruning don't affect behaviour,
+  /// so use the default values so they may be dropped from the command-line.
+  getHeaderSearchOpts().ModuleCachePruneInterval = 7 * 24 * 60 * 60;
+  getHeaderSearchOpts().ModuleCachePruneAfter = 31 * 24 * 60 * 60;
+}
+
 IntrusiveRefCntPtr<llvm::vfs::FileSystem>
 clang::createVFSFromCompilerInvocation(const CompilerInvocation &CI,
                                        DiagnosticsEngine &Diags) {
Index: clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
===================================================================
--- clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
+++ clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
@@ -88,8 +88,8 @@
   // Make a deep copy of the original Clang invocation.
   CompilerInvocation CI(OriginalInvocation);
 
-  CI.getLangOpts()->resetNonModularOptions();
-  CI.getPreprocessorOpts().resetNonModularOptions();
+  CI.resetNonModularOptions();
+  CI.clearImplicitModuleBuildOptions();
 
   // Remove options incompatible with explicit module build or are likely to
   // differ between identical modules discovered from different translation
@@ -110,18 +110,6 @@
   CI.getLangOpts()->ModuleName = Deps.ID.ModuleName;
   CI.getFrontendOpts().IsSystemModule = Deps.IsSystem;
 
-  // Disable implicit modules and canonicalize options that are only used by
-  // implicit modules.
-  CI.getLangOpts()->ImplicitModules = false;
-  CI.getHeaderSearchOpts().ImplicitModuleMaps = false;
-  CI.getHeaderSearchOpts().ModuleCachePath.clear();
-  CI.getHeaderSearchOpts().ModulesValidateOncePerBuildSession = false;
-  CI.getHeaderSearchOpts().BuildSessionTimestamp = 0;
-  // The specific values we canonicalize to for pruning don't affect behaviour,
-  /// so use the default values so they will be dropped from the command-line.
-  CI.getHeaderSearchOpts().ModuleCachePruneInterval = 7 * 24 * 60 * 60;
-  CI.getHeaderSearchOpts().ModuleCachePruneAfter = 31 * 24 * 60 * 60;
-
   // Inputs
   InputKind ModuleMapInputKind(CI.getFrontendOpts().DashX.getLanguage(),
                                InputKind::Format::ModuleMap);
@@ -159,23 +147,8 @@
   return CI;
 }
 
-static std::vector<std::string>
-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() const {
-  return serializeCompilerInvocation(BuildInvocation);
+  return BuildInvocation.getCC1CommandLine();
 }
 
 static std::string getModuleContextHash(const ModuleDeps &MD) {