3 files changed, 9 insertions, 15 deletions
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index dcc824723aa..a5165ad6211 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -371,6 +371,14 @@ void CompilerInstance::createPreprocessor(TranslationUnitKind TUKind) {
     AttachHeaderIncludeGen(*PP, /*ShowAllHeaders=*/false, /*OutputPath=*/"",
                            /*ShowDepth=*/true, /*MSStyle=*/true);
   }
+
+  // Load all explictly-specified module map files.
+  for (const auto &Filename : getFrontendOpts().ModuleMapFiles) {
+    if (auto *File = getFileManager().getFile(Filename))
+      PP->getHeaderSearchInfo().loadModuleMapFile(File, /*IsSystem*/false);
+    else
+      getDiagnostics().Report(diag::err_module_map_not_found) << Filename;
+  }
 }
 
 // ASTContext
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 65ffd5475ca..f01663858e0 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -848,6 +848,7 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
   Opts.ASTDumpLookups = Args.hasArg(OPT_ast_dump_lookups);
   Opts.UseGlobalModuleIndex = !Args.hasArg(OPT_fno_modules_global_index);
   Opts.GenerateGlobalModuleIndex = Opts.UseGlobalModuleIndex;
+  Opts.ModuleMapFiles = Args.getAllArgValues(OPT_fmodule_map_file);
   Opts.ModuleFiles = Args.getAllArgValues(OPT_fmodule_file);
 
   Opts.CodeCompleteOpts.IncludeMacros
@@ -1019,9 +1020,6 @@ static void ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args) {
     StringRef MacroDef = (*it)->getValue();
     Opts.ModulesIgnoreMacros.insert(MacroDef.split('=').first);
   }
-  std::vector<std::string> ModuleMapFiles =
-      Args.getAllArgValues(OPT_fmodule_map_file);
-  Opts.ModuleMapFiles.insert(ModuleMapFiles.begin(), ModuleMapFiles.end());
 
   // Add -I..., -F..., and -index-header-map options in order.
   bool IsIndexHeaderMap = false;
diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index bbbcf3abec6..a3f3737521e 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -569,18 +569,6 @@ const FileEntry *HeaderSearch::LookupFile(
     ArrayRef<std::pair<const FileEntry *, const DirectoryEntry *>> Includers,
     SmallVectorImpl<char> *SearchPath, SmallVectorImpl<char> *RelativePath,
     ModuleMap::KnownHeader *SuggestedModule, bool SkipCache) {
-  if (!HSOpts->ModuleMapFiles.empty()) {
-    // Preload all explicitly specified module map files. This enables modules
-    // map files lying in a directory structure separate from the header files
-    // that they describe. These cannot be loaded lazily upon encountering a
-    // header file, as there is no other known mapping from a header file to its
-    // module map file.
-    for (const auto &Filename : HSOpts->ModuleMapFiles)
-      if (const FileEntry *File = FileMgr.getFile(Filename))
-        loadModuleMapFile(File, /*IsSystem=*/false);
-    HSOpts->ModuleMapFiles.clear();
-  }
-
   if (SuggestedModule)
     *SuggestedModule = ModuleMap::KnownHeader();