4 files changed, 21 insertions, 3 deletions
diff --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
index 8954c8fb9f0..32894f2eb56 100644
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -678,6 +678,13 @@ void SourceManager::disableFileContentsOverride(const FileEntry *File) {
   OverriddenFilesInfo->OverriddenFilesWithBuffer.erase(File);
 }
 
+void SourceManager::embedFileContentsInModule(const FileEntry *File) {
+  // We model an embedded file as a file whose buffer has been overridden
+  // by its contents as they are now.
+  const SrcMgr::ContentCache *CC = getOrCreateContentCache(File);
+  const_cast<SrcMgr::ContentCache *>(CC)->BufferOverridden = true;
+}
+
 StringRef SourceManager::getBufferData(FileID FID, bool *Invalid) const {
   bool MyInvalid = false;
   const SLocEntry &SLoc = getSLocEntry(FID, &MyInvalid);
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 73febb463ec..f078b37c3c2 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -960,6 +960,7 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
   Opts.GenerateGlobalModuleIndex = Opts.UseGlobalModuleIndex;
   Opts.ModuleMapFiles = Args.getAllArgValues(OPT_fmodule_map_file);
   Opts.ModuleFiles = Args.getAllArgValues(OPT_fmodule_file);
+  Opts.ModulesEmbedFiles = Args.getAllArgValues(OPT_fmodules_embed_file_EQ);
 
   Opts.CodeCompleteOpts.IncludeMacros
     = Args.hasArg(OPT_code_completion_macros);
diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
index 40277bdaa52..057361811ba 100644
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -268,8 +268,9 @@ collectModuleHeaderIncludes(const LangOptions &LangOpts, FileManager &FileMgr,
 
 bool GenerateModuleAction::BeginSourceFileAction(CompilerInstance &CI, 
                                                  StringRef Filename) {
-  // Find the module map file.  
-  const FileEntry *ModuleMap = CI.getFileManager().getFile(Filename);
+  // Find the module map file.
+  const FileEntry *ModuleMap =
+      CI.getFileManager().getFile(Filename, /*openFile*/true);
   if (!ModuleMap)  {
     CI.getDiagnostics().Report(diag::err_module_map_not_found)
       << Filename;
@@ -291,6 +292,14 @@ bool GenerateModuleAction::BeginSourceFileAction(CompilerInstance &CI,
     return false;
   }
 
+  // Set up embedding for any specified files.
+  for (const auto &F : CI.getFrontendOpts().ModulesEmbedFiles) {
+    if (const auto *FE = CI.getFileManager().getFile(F, /*openFile*/true))
+      CI.getSourceManager().embedFileContentsInModule(FE);
+    else
+      CI.getDiagnostics().Report(diag::err_modules_embed_file_not_found) << F;
+  }
+
   // If we're being run from the command-line, the module build stack will not
   // have been filled in yet, so complete it now in order to allow us to detect
   // module cycles.
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 87db6d3b4de..547dda73f73 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -1023,7 +1023,8 @@ bool ASTReader::ReadVisibleDeclContextStorage(ModuleFile &M,
 
 void ASTReader::Error(StringRef Msg) {
   Error(diag::err_fe_pch_malformed, Msg);
-  if (Context.getLangOpts().Modules && !Diags.isDiagnosticInFlight()) {
+  if (Context.getLangOpts().Modules && !Diags.isDiagnosticInFlight() &&
+      !PP.getHeaderSearchInfo().getModuleCachePath().empty()) {
     Diag(diag::note_module_cache_path)
       << PP.getHeaderSearchInfo().getModuleCachePath();
   }