Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -555,6 +555,8 @@
 def PessimizingMove : DiagGroup<"pessimizing-move">;
 def ReturnStdMove : DiagGroup<"return-std-move">;
 
+def PessimizingReturnByConst : DiagGroup<"pessimizing-return-by-const">;
+
 def GNUPointerArith : DiagGroup<"gnu-pointer-arith">;
 def PointerArith : DiagGroup<"pointer-arith", [GNUPointerArith]>;
 
@@ -990,6 +992,7 @@
     MissingBraces,
     Move,
     MultiChar,
+    PessimizingReturnByConst,
     RangeLoopConstruct,
     Reorder,
     ReturnType,
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6627,6 +6627,13 @@
   InGroup<PessimizingMove>, DefaultIgnore;
 def note_remove_move : Note<"remove std::move call here">;
 
+def warn_pessimizing_return_by_const : Warning<
+  "const qualifying the return value prevents move semantics">,
+  InGroup<PessimizingReturnByConst>, DefaultIgnore;
+def note_pessimizing_return_by_const : Note<
+  "copy assignment is invoked here even if move assignment "
+  "is supported for type %0">;
+
 def warn_string_plus_int : Warning<
   "adding %0 to a string does not append to the string">,
   InGroup<StringPlusInt>;
Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -5070,6 +5070,9 @@
   void DiagnoseSelfMove(const Expr *LHSExpr, const Expr *RHSExpr,
                         SourceLocation OpLoc);
 
+  void DiagnosePessimizingConstReturn(const Expr *RHSExpr,
+                                      SourceLocation OpLoc);
+
   /// Warn if we're implicitly casting from a _Nullable pointer type to a
   /// _Nonnull one.
   void diagnoseNullableToNonnullConversion(QualType DstType, QualType SrcType,
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -16800,6 +16800,47 @@
                                         << RHSExpr->getSourceRange();
 }
 
+void Sema::DiagnosePessimizingConstReturn(const Expr *RHSExpr,
+                                          SourceLocation OpLoc) {
+  if (!getLangOpts().CPlusPlus11 || inTemplateInstantiation())
+    return;
+
+  RHSExpr = RHSExpr->IgnoreParenImpCasts();
+
+  // Is RHS a function call expression?
+  const CallExpr *CE = dyn_cast<const CallExpr>(RHSExpr);
+  if (!CE)
+    return;
+
+  const Decl *CD = CE->getCalleeDecl();
+  if (!CD)
+    return;
+
+  const FunctionDecl *FD = dyn_cast<const FunctionDecl>(CD);
+  if (!FD)
+    return;
+
+  // Is the return type by-const-value of a struct or class type?
+  const QualType RT = FD->getReturnType();
+  if (!RT->isStructureOrClassType() || !RT.isConstQualified())
+    return;
+
+  // Is the move assignment operator deleted?
+  bool MoveAssignmentIsDeleted = false;
+  for (const CXXMethodDecl *iter : RT->getAsCXXRecordDecl()->methods())
+    if (iter->isMoveAssignmentOperator() && iter->isDeleted())
+      MoveAssignmentIsDeleted = true;
+
+  if (RT->getAsCXXRecordDecl()->hasDefinition() &&
+      RT->getAsCXXRecordDecl()->hasMoveAssignment() &&
+      !MoveAssignmentIsDeleted) {
+    const SourceRange ReturnTypeLoc = FD->getReturnTypeSourceRange();
+    Diag(ReturnTypeLoc.getBegin(), diag::warn_pessimizing_return_by_const);
+    Diag(OpLoc, diag::note_pessimizing_return_by_const)
+        << RT.getUnqualifiedType();
+  }
+}
+
 //===--- Layout compatibility ----------------------------------------------//
 
 static bool isLayoutCompatible(ASTContext &C, QualType T1, QualType T2);
Index: clang/lib/Sema/SemaOverload.cpp
===================================================================
--- clang/lib/Sema/SemaOverload.cpp
+++ clang/lib/Sema/SemaOverload.cpp
@@ -13810,9 +13810,10 @@
           ArgsArray = ArgsArray.slice(1);
         }
 
-        // Check for a self move.
-        if (Op == OO_Equal)
+        if (Op == OO_Equal) {
           DiagnoseSelfMove(Args[0], Args[1], OpLoc);
+          DiagnosePessimizingConstReturn(Args[1], OpLoc);
+        }
 
         if (ImplicitThis) {
           QualType ThisType = Context.getPointerType(ImplicitThis->getType());
Index: clang/test/Misc/warning-wall.c
===================================================================
--- clang/test/Misc/warning-wall.c
+++ clang/test/Misc/warning-wall.c
@@ -33,6 +33,7 @@
 CHECK-NEXT:      -Wreturn-std-move
 CHECK-NEXT:      -Wself-move
 CHECK-NEXT:    -Wmultichar
+CHECK-NEXT:    -Wpessimizing-return-by-const
 CHECK-NEXT:    -Wrange-loop-construct
 CHECK-NEXT:    -Wreorder
 CHECK-NEXT:      -Wreorder-ctor
Index: clang/test/SemaCXX/warn-pessimizing-return-by-const.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/warn-pessimizing-return-by-const.cpp
@@ -0,0 +1,58 @@
+// RUN: %clang_cc1 -fsyntax-only -Wpessimizing-return-by-const -std=c++11 -verify %s
+
+struct S1 {};
+
+S1 f1() {
+  return S1{};
+}
+
+const S1 f1_const() { // expected-warning{{const qualifying the return value prevents move semantics}}
+  return S1{};
+}
+
+void run1() {
+  S1 s1;
+  s1 = f1();
+  s1 = f1_const(); // expected-note{{copy assignment is invoked here even if move assignment is supported for type 'S1'}}
+}
+
+struct S2 {
+  S2() = default;
+  S2(const S2 &) = default;
+  S2 &operator=(const S2 &) = default;
+  S2 &operator=(S2 &&) = default;
+};
+
+S2 f2() {
+  return S2{};
+}
+
+const S2 f2_const() { // expected-warning{{const qualifying the return value prevents move semantics}}
+  return S2{};
+}
+
+void run2() {
+  S2 s2;
+  s2 = f2();
+  s2 = f2_const(); // expected-note{{copy assignment is invoked here even if move assignment is supported for type 'S2'}}
+}
+
+struct S3 {
+  S3() = default;
+  S3(const S3 &) = default;
+  S3 &operator=(const S3 &) = default;
+};
+
+S3 f3() {
+  return S3{};
+}
+
+const S3 f3_const() { // do not warn if move assignment operator is deleted
+  return S3{};
+}
+
+void run3() {
+  S3 s3;
+  s3 = f3();
+  s3 = f3_const();
+}