Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -5688,6 +5688,21 @@
           cast<InheritableAttr>(ClassAttr->clone(getASTContext()));
       NewAttr->setInherited(true);
       Member->addAttr(NewAttr);
+
+      if (MD) {
+        // Propagate DLLAttr to friend re-declarations of MD that have already
+        // been constructed.
+        for (FunctionDecl *FD = MD->getMostRecentDecl(); FD;
+             FD = FD->getPreviousDecl()) {
+          if (FD->getFriendObjectKind() == Decl::FOK_None)
+            continue;
+          assert(!getDLLAttr(FD) &&
+                 "friend re-decl should not already have a DLLAttr");
+          NewAttr = cast<InheritableAttr>(ClassAttr->clone(getASTContext()));
+          NewAttr->setInherited(true);
+          FD->addAttr(NewAttr);
+        }
+      }
     }
   }
 
Index: clang/test/CodeGenCXX/dllexport.cpp
===================================================================
--- clang/test/CodeGenCXX/dllexport.cpp
+++ clang/test/CodeGenCXX/dllexport.cpp
@@ -290,6 +290,16 @@
 __declspec(dllexport) void friend1() {}
                       void friend2() {}
 
+// MSC-DAG: define dso_local dllexport void @"\01?func@Befriended@@SAXXZ"()
+// GNU-DAG: define dso_local dllexport void @_ZN10Befriended4funcEv()
+struct __declspec(dllexport) Befriended {
+  static void func();
+  struct Befriending {
+    friend void Befriended::func();
+  };
+};
+void Befriended::func() {}
+
 // Implicit declarations can be redeclared with dllexport.
 // MSC-DAG: define dso_local dllexport noalias i8* @"\01??2@{{YAPAXI|YAPEAX_K}}@Z"(
 // GNU-DAG: define dso_local dllexport noalias i8* @_Znw{{[yj]}}(