Index: clang/lib/CodeGen/CGObjC.cpp
===================================================================
--- clang/lib/CodeGen/CGObjC.cpp
+++ clang/lib/CodeGen/CGObjC.cpp
@@ -2446,21 +2446,37 @@
     EHStack.pushCleanup<CallObjCMRRAutoreleasePoolObject>(NormalCleanup, Ptr);
 }
 
+static bool shouldRetainObjCLifetime(Qualifiers::ObjCLifetime Lifetime) {
+  switch (Lifetime) {
+  case Qualifiers::OCL_None:
+  case Qualifiers::OCL_ExplicitNone:
+  case Qualifiers::OCL_Strong:
+  case Qualifiers::OCL_Autoreleasing:
+    return true;
+
+  case Qualifiers::OCL_Weak:
+    return false;
+  }
+
+  llvm_unreachable("impossible lifetime!");
+}
+
 static TryEmitResult tryEmitARCRetainLoadOfScalar(CodeGenFunction &CGF,
                                                   LValue lvalue,
                                                   QualType type) {
+  bool SuppressResultRetain = !shouldRetainObjCLifetime(type.getObjCLifetime());
   switch (type.getObjCLifetime()) {
   case Qualifiers::OCL_None:
   case Qualifiers::OCL_ExplicitNone:
   case Qualifiers::OCL_Strong:
   case Qualifiers::OCL_Autoreleasing:
-    return TryEmitResult(CGF.EmitLoadOfLValue(lvalue,
-                                              SourceLocation()).getScalarVal(),
-                         false);
+    return TryEmitResult(
+        CGF.EmitLoadOfLValue(lvalue, SourceLocation()).getScalarVal(),
+        SuppressResultRetain);
 
   case Qualifiers::OCL_Weak:
     return TryEmitResult(CGF.EmitARCLoadWeakRetained(lvalue.getAddress()),
-                         true);
+                         SuppressResultRetain);
   }
 
   llvm_unreachable("impossible lifetime!");
@@ -2500,6 +2516,17 @@
       cast<BinaryOperator>(e)->getOpcode() == BO_Assign)
     return TryEmitResult(CGF.EmitScalarExpr(e), false);
 
+  // DeclRefExpr referencing non-odr-used variable might be constant-evaluated
+  // and in this case we don't have l-value. Emit code for scalar expression
+  // instead of emitting LValue and loading it.
+  if (const auto *DRE = dyn_cast<DeclRefExpr>(e)) {
+    const ValueDecl *Decl = DRE->getDecl();
+    if (isa<VarDecl>(Decl) && !Decl->isUsed(false) &&
+        !Decl->getType()->isReferenceType())
+      return TryEmitResult(CGF.EmitScalarExpr(e),
+                           !shouldRetainObjCLifetime(type.getObjCLifetime()));
+  }
+
   return tryEmitARCRetainLoadOfScalar(CGF, CGF.EmitLValue(e), type);
 }
 
Index: clang/test/CodeGenObjCXX/arc-constexpr.mm
===================================================================
--- clang/test/CodeGenObjCXX/arc-constexpr.mm
+++ clang/test/CodeGenObjCXX/arc-constexpr.mm
@@ -1,18 +1,50 @@
-// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -fobjc-arc -o - -std=c++11 %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -fobjc-arc -fobjc-runtime-has-weak -o - -std=c++11 %s | FileCheck %s
 
 // CHECK: %[[TYPE:[a-z0-9]+]] = type opaque
 // CHECK: @[[CFSTRING:[a-z0-9_]+]] = private global %struct.__NSConstantString_tag
+@class NSString;
 
-// CHECK: define void @_Z5test1v
+// CHECK-LABEL: define void @_Z5test1v
 // CHECK:   %[[ALLOCA:[A-Z]+]] = alloca %[[TYPE]]*
 // CHECK:   %[[V0:[0-9]+]] = call i8* @objc_retain(i8* bitcast (%struct.__NSConstantString_tag* @[[CFSTRING]]
 // CHECK:   %[[V1:[0-9]+]] = bitcast i8* %[[V0]] to %[[TYPE]]*
 // CHECK:   store %[[TYPE]]* %[[V1]], %[[TYPE]]** %[[ALLOCA]]
 // CHECK:   %[[V2:[0-9]+]] = bitcast %[[TYPE]]** %[[ALLOCA]]
 // CHECK:   call void @objc_storeStrong(i8** %[[V2]], i8* null)
-
-@class NSString;
-
 void test1() {
   constexpr NSString *S = @"abc";
 }
+
+// CHECK-LABEL: define void @_Z5test2v
+// CHECK:      %[[CONST:[a-zA-Z]+]] = alloca %[[TYPE]]*
+// CHECK:      %[[REF_CONST:[a-zA-Z]+]] = alloca %[[TYPE]]*
+// CHECK:      %[[V0:[0-9]+]] = call i8* @objc_retain(i8* bitcast (%struct.__NSConstantString_tag* @[[CFSTRING]]
+// CHECK-NEXT: %[[V1:[0-9]+]] = bitcast i8* %[[V0]] to %[[TYPE]]*
+// CHECK-NEXT: store %[[TYPE]]* %[[V1]], %[[TYPE]]** %[[CONST]]
+// CHECK:      %[[V2:[0-9]+]] = call i8* @objc_retain(i8* bitcast (%struct.__NSConstantString_tag* @[[CFSTRING]]
+// CHECK-NEXT: %[[V3:[0-9]+]] = bitcast i8* %[[V2]] to %[[TYPE]]*
+// CHECK-NEXT: store %[[TYPE]]* %[[V3]], %[[TYPE]]** %[[REF_CONST]]
+// CHECK:      %[[V4:[0-9]+]] = bitcast %[[TYPE]]** %[[REF_CONST]]
+// CHECK-NEXT: call void @objc_storeStrong(i8** %[[V4]], i8* null)
+// CHECK:      %[[V5:[0-9]+]] = bitcast %[[TYPE]]** %[[CONST]]
+// CHECK-NEXT: call void @objc_storeStrong(i8** %[[V5]], i8* null)
+void test2() {
+  constexpr NSString *Const = @"abc";
+  // Initialize RefConst with Const initializer instead of reading from variable.
+  NSString* RefConst = Const;
+}
+
+// CHECK-LABEL: define void @_Z5test3v
+// CHECK:      %[[WEAK_CONST:[a-zA-Z]+]] = alloca %[[TYPE]]*
+// CHECK:      %[[REF_WEAK_CONST:[a-zA-Z]+]] = alloca %[[TYPE]]*
+// CHECK:      %[[V0:[0-9]+]] = bitcast %[[TYPE]]** %[[WEAK_CONST]]
+// CHECK-NEXT: %[[V1:[0-9]+]] = call i8* @objc_initWeak(i8** %[[V0]], i8* bitcast (%struct.__NSConstantString_tag* @[[CFSTRING]]
+// CHECK:      store %[[TYPE]]* bitcast (%struct.__NSConstantString_tag* @[[CFSTRING]] to %[[TYPE]]*), %[[TYPE]]** %[[REF_WEAK_CONST]]
+// CHECK:      %[[V2:[0-9]+]] = bitcast %[[TYPE]]** %[[REF_WEAK_CONST]]
+// CHECK-NEXT: call void @objc_storeStrong(i8** %[[V2]], i8* null)
+// CHECK:      %[[V3:[0-9]+]] = bitcast %[[TYPE]]** %[[WEAK_CONST]]
+// CHECK-NEXT: call void @objc_destroyWeak(i8** %[[V3]])
+void test3() {
+  __weak constexpr NSString *WeakConst = @"abc";
+  NSString* RefWeakConst = WeakConst;
+}