Index: include/clang/Index/IndexingAction.h
===================================================================
--- include/clang/Index/IndexingAction.h
+++ include/clang/Index/IndexingAction.h
@@ -11,12 +11,15 @@
 #define LLVM_CLANG_INDEX_INDEXINGACTION_H
 
 #include "clang/Basic/LLVM.h"
+#include <llvm/ADT/ArrayRef.h>
 #include <memory>
 
 namespace clang {
   class ASTReader;
   class ASTUnit;
   class FrontendAction;
+  class ASTContext;
+  class Decl;
 
 namespace serialization {
   class ModuleFile;
@@ -47,8 +50,11 @@
                   std::shared_ptr<IndexDataConsumer> DataConsumer,
                   IndexingOptions Opts);
 
-void indexModuleFile(serialization::ModuleFile &Mod,
-                     ASTReader &Reader,
+void indexTopLevelDecls(ASTContext &Ctx, ArrayRef<const Decl *> Decls,
+                        std::shared_ptr<IndexDataConsumer> DataConsumer,
+                        IndexingOptions Opts);
+
+void indexModuleFile(serialization::ModuleFile &Mod, ASTReader &Reader,
                      std::shared_ptr<IndexDataConsumer> DataConsumer,
                      IndexingOptions Opts);
 
Index: lib/Index/IndexingAction.cpp
===================================================================
--- lib/Index/IndexingAction.cpp
+++ lib/Index/IndexingAction.cpp
@@ -177,6 +177,18 @@
   DataConsumer->finish();
 }
 
+void index::indexTopLevelDecls(ASTContext &Ctx, ArrayRef<const Decl *> Decls,
+                        std::shared_ptr<IndexDataConsumer> DataConsumer,
+                        IndexingOptions Opts) {
+  IndexingContext IndexCtx(Opts, *DataConsumer);
+  IndexCtx.setASTContext(Ctx);
+
+  DataConsumer->initialize(Ctx);
+  for (const Decl *D : Decls)
+    IndexCtx.indexTopLevelDecl(D);
+  DataConsumer->finish();
+}
+
 void index::indexModuleFile(serialization::ModuleFile &Mod,
                             ASTReader &Reader,
                             std::shared_ptr<IndexDataConsumer> DataConsumer,