diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -1431,9 +1431,13 @@
     }
     int count(Selector Sel) const { return Methods.count(Sel); }
     bool empty() const { return Methods.empty(); }
+    bool addMethod(ObjCMethodDecl *Method) {
+      return AddedMethods.insert(Method).second;
+    }
 
   private:
     llvm::DenseMap<Selector, Lists> Methods;
+    llvm::DenseSet<ObjCMethodDecl *> AddedMethods;
   };
 
   /// Method Pool - allows efficient lookup when typechecking messages to "id".
diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -3302,6 +3302,10 @@
 
 void Sema::addMethodToGlobalList(ObjCMethodList *List,
                                  ObjCMethodDecl *Method) {
+  // Do not insert duplicate methods into the method pool.
+  if (!MethodPool.addMethod(Method))
+    return;
+
   // Record at the head of the list whether there were 0, 1, or >= 2 methods
   // inside categories.
   if (ObjCCategoryDecl *CD =