3 files changed, 22 insertions, 2 deletions
diff --git a/lib/Frontend/CompilerInstance.cpp b/lib/Frontend/CompilerInstance.cpp
index 9941eae8d4..07c0248b6c 100644
--- a/lib/Frontend/CompilerInstance.cpp
+++ b/lib/Frontend/CompilerInstance.cpp
@@ -48,7 +48,8 @@
 using namespace clang;
 
 CompilerInstance::CompilerInstance()
-  : Invocation(new CompilerInvocation()), ModuleManager(0) {
+  : Invocation(new CompilerInvocation()), ModuleManager(0),
+    BuildGlobalModuleIndex(false) {
 }
 
 CompilerInstance::~CompilerInstance() {
@@ -785,6 +786,7 @@ static void compileModule(CompilerInstance &ImportingInstance,
   FrontendOptions &FrontendOpts = Invocation->getFrontendOpts();
   FrontendOpts.OutputFile = ModuleFileName.str();
   FrontendOpts.DisableFree = false;
+  FrontendOpts.GenerateModuleIndex = false;
   FrontendOpts.Inputs.clear();
   InputKind IK = getSourceInputKindFromOptions(*Invocation->getLangOpts());
 
@@ -858,6 +860,12 @@ static void compileModule(CompilerInstance &ImportingInstance,
   Instance.clearOutputFiles(/*EraseFiles=*/true);
   if (!TempModuleMapFileName.empty())
     llvm::sys::Path(TempModuleMapFileName).eraseFromDisk();
+
+  // We've rebuilt a module. If we're allowed to generate or update the global
+  // module index, record that fact in the importing compiler instance.
+  if (ImportingInstance.getFrontendOpts().GenerateModuleIndex) {
+    ImportingInstance.setBuildGlobalModuleIndex(true);
+  }
 }
 
 ModuleLoadResult
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index eab9cc3cf1..011e3e1538 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -705,7 +705,8 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
   Opts.FixAndRecompile = Args.hasArg(OPT_fixit_recompile);
   Opts.FixToTemporaries = Args.hasArg(OPT_fixit_to_temp);
   Opts.ASTDumpFilter = Args.getLastArgValue(OPT_ast_dump_filter);
-
+  Opts.GenerateModuleIndex = Args.hasArg(OPT_generate_module_index);
+  
   Opts.CodeCompleteOpts.IncludeMacros
     = Args.hasArg(OPT_code_completion_macros);
   Opts.CodeCompleteOpts.IncludeCodePatterns
diff --git a/lib/Frontend/FrontendAction.cpp b/lib/Frontend/FrontendAction.cpp
index 742caf158b..4b642b395c 100644
--- a/lib/Frontend/FrontendAction.cpp
+++ b/lib/Frontend/FrontendAction.cpp
@@ -23,6 +23,7 @@
 #include "clang/Parse/ParseAST.h"
 #include "clang/Serialization/ASTDeserializationListener.h"
 #include "clang/Serialization/ASTReader.h"
+#include "clang/Serialization/GlobalModuleIndex.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -380,6 +381,16 @@ bool FrontendAction::Execute() {
   }
   else ExecuteAction();
 
+  // If we are supposed to rebuild the global module index, do so now unless
+  // an error occurred.
+  if (CI.getBuildGlobalModuleIndex() && CI.hasFileManager() &&
+      CI.hasPreprocessor() &&
+      (!CI.hasDiagnostics() || !CI.getDiagnostics().hasErrorOccurred())) {
+    GlobalModuleIndex::writeIndex(
+      CI.getFileManager(),
+      CI.getPreprocessor().getHeaderSearchInfo().getModuleCachePath());
+  }
+
   return true;
 }