[PCH+Modules] Load -fmodule-map-file content before including PCHs

Consider:
1) Generate PCH with -fmodules and -fmodule-map-file
2) Use PCH with -fmodules and the same -fmodule-map-file

If we don't load -fmodule-map-file content before including PCHs,
the modules that are dependencies in PCHs cannot get loaded,
since there's no matching module map file when reading back the AST.

rdar://problem/40852867

Differential Revision: https://reviews.llvm.org/D48685

llvm-svn: 337447

1 files changed, 16 insertions, 16 deletions

diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index 7711d8460c5..a5929424e52 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -766,6 +766,22 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
   if (!BeginSourceFileAction(CI))
     goto failure;
 
+  // If we were asked to load any module map files, do so now.
+  for (const auto &Filename : CI.getFrontendOpts().ModuleMapFiles) {
+    if (auto *File = CI.getFileManager().getFile(Filename))
+      CI.getPreprocessor().getHeaderSearchInfo().loadModuleMapFile(
+          File, /*IsSystem*/false);
+    else
+      CI.getDiagnostics().Report(diag::err_module_map_not_found) << Filename;
+  }
+
+  // Add a module declaration scope so that modules from -fmodule-map-file
+  // arguments may shadow modules found implicitly in search paths.
+  CI.getPreprocessor()
+      .getHeaderSearchInfo()
+      .getModuleMap()
+      .finishModuleDeclarationScope();
+
   // Create the AST context and consumer unless this is a preprocessor only
   // action.
   if (!usesPreprocessorOnly()) {
@@ -855,22 +871,6 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
            "doesn't support modules");
   }
 
-  // If we were asked to load any module map files, do so now.
-  for (const auto &Filename : CI.getFrontendOpts().ModuleMapFiles) {
-    if (auto *File = CI.getFileManager().getFile(Filename))
-      CI.getPreprocessor().getHeaderSearchInfo().loadModuleMapFile(
-          File, /*IsSystem*/false);
-    else
-      CI.getDiagnostics().Report(diag::err_module_map_not_found) << Filename;
-  }
-
-  // Add a module declaration scope so that modules from -fmodule-map-file
-  // arguments may shadow modules found implicitly in search paths.
-  CI.getPreprocessor()
-      .getHeaderSearchInfo()
-      .getModuleMap()
-      .finishModuleDeclarationScope();
-
   // If we were asked to load any module files, do so now.
   for (const auto &ModuleFile : CI.getFrontendOpts().ModuleFiles)
     if (!CI.loadModuleFile(ModuleFile))