diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index c78b407..3d3dbae 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -69,6 +69,15 @@
    ``\returns`` documentation directives in the documentation comments for
    declarations with a function or a block pointer type.
 
+- ``-Wobjc-messaging-id`` is a new, non-default warning that warns about
+  message sends to unqualified ``id`` in Objective-C. This warning is useful
+  for projects that would like to avoid any potential future compiler
+  errors/warnings, as the system frameworks might add a method with the same
+  selector which could make the message send to ``id`` ambiguous.
+
+Non-comprehensive list of changes in this release
+-------------------------------------------------
+
 -  The compiler no longer warns about unreachable ``__builtin_unreachable``
    statements.
 
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index fd992e7..14b6e61 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1201,6 +1201,10 @@
   "%0 %select{parameter|return}1 type is unsupported; "
   "support for vector types for this target is introduced in %2">;
 
+def warn_messaging_unqualified_id : Warning<
+  "messaging unqualified id">, DefaultIgnore,
+  InGroup<DiagGroup<"objc-messaging-id">>;
+
 // C++ declarations
 def err_static_assert_expression_is_not_constant : Error<
   "static_assert expression is not an integral constant expression">;
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 240ecfb..cea0516 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1339,6 +1339,25 @@
   return ConstantEmission::forValue(C);
 }
 
+static DeclRefExpr *tryToConvertMemberExprToDeclRefExpr(CodeGenFunction &CGF,
+                                                        const MemberExpr *ME) {
+  if (auto *VD = dyn_cast<VarDecl>(ME->getMemberDecl())) {
+    // Try to emit static variable member expressions as DREs.
+    return DeclRefExpr::Create(
+        CGF.getContext(), NestedNameSpecifierLoc(), SourceLocation(), VD,
+        /*RefersToEnclosingVariableOrCapture=*/false, ME->getExprLoc(),
+        ME->getType(), ME->getValueKind());
+  }
+  return nullptr;
+}
+
+CodeGenFunction::ConstantEmission
+CodeGenFunction::tryEmitAsConstant(const MemberExpr *ME) {
+  if (DeclRefExpr *DRE = tryToConvertMemberExprToDeclRefExpr(*this, ME))
+    return tryEmitAsConstant(DRE);
+  return ConstantEmission();
+}
+
 llvm::Value *CodeGenFunction::EmitLoadOfScalar(LValue lvalue,
                                                SourceLocation Loc) {
   return EmitLoadOfScalar(lvalue.getAddress(), lvalue.isVolatile(),
@@ -3539,6 +3558,11 @@
 }
 
 LValue CodeGenFunction::EmitMemberExpr(const MemberExpr *E) {
+  if (DeclRefExpr *DRE = tryToConvertMemberExprToDeclRefExpr(*this, E)) {
+    EmitIgnoredExpr(E->getBase());
+    return EmitDeclRefLValue(DRE);
+  }
+
   Expr *BaseExpr = E->getBase();
   // If this is s.x, emit s as an lvalue.  If it is s->x, emit s as a scalar.
   LValue BaseLV;
@@ -3565,9 +3589,6 @@
     return LV;
   }
 
-  if (auto *VD = dyn_cast<VarDecl>(ND))
-    return EmitGlobalVarDeclLValue(*this, E, VD);
-
   if (const auto *FD = dyn_cast<FunctionDecl>(ND))
     return EmitFunctionDeclLValue(*this, E, FD);
 
diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index a05a088..1ab8433 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -124,24 +124,7 @@
   }
 
   // l-values.
-  void VisitDeclRefExpr(DeclRefExpr *E) {
-    // For aggregates, we should always be able to emit the variable
-    // as an l-value unless it's a reference.  This is due to the fact
-    // that we can't actually ever see a normal l2r conversion on an
-    // aggregate in C++, and in C there's no language standard
-    // actively preventing us from listing variables in the captures
-    // list of a block.
-    if (E->getDecl()->getType()->isReferenceType()) {
-      if (CodeGenFunction::ConstantEmission result
-            = CGF.tryEmitAsConstant(E)) {
-        EmitFinalDestCopy(E->getType(), result.getReferenceLValue(CGF, E));
-        return;
-      }
-    }
-
-    EmitAggLoadOfLValue(E);
-  }
-
+  void VisitDeclRefExpr(DeclRefExpr *E) { EmitAggLoadOfLValue(E); }
   void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
   void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
   void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
diff --git a/lib/CodeGen/CGExprComplex.cpp b/lib/CodeGen/CGExprComplex.cpp
index 9809723..f019e35 100644
--- a/lib/CodeGen/CGExprComplex.cpp
+++ b/lib/CodeGen/CGExprComplex.cpp
@@ -120,18 +120,22 @@
     return Visit(E->getSubExpr());
   }
 
+  ComplexPairTy emitConstant(const CodeGenFunction::ConstantEmission &Constant,
+                             Expr *E) {
+    assert(Constant && "not a constant");
+    if (Constant.isReference())
+      return EmitLoadOfLValue(Constant.getReferenceLValue(CGF, E),
+                              E->getExprLoc());
+
+    llvm::Constant *pair = Constant.getValue();
+    return ComplexPairTy(pair->getAggregateElement(0U),
+                         pair->getAggregateElement(1U));
+  }
 
   // l-values.
   ComplexPairTy VisitDeclRefExpr(DeclRefExpr *E) {
-    if (CodeGenFunction::ConstantEmission result = CGF.tryEmitAsConstant(E)) {
-      if (result.isReference())
-        return EmitLoadOfLValue(result.getReferenceLValue(CGF, E),
-                                E->getExprLoc());
-
-      llvm::Constant *pair = result.getValue();
-      return ComplexPairTy(pair->getAggregateElement(0U),
-                           pair->getAggregateElement(1U));
-    }
+    if (CodeGenFunction::ConstantEmission Constant = CGF.tryEmitAsConstant(E))
+      return emitConstant(Constant, E);
     return EmitLoadOfLValue(E);
   }
   ComplexPairTy VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
@@ -141,7 +145,14 @@
     return CGF.EmitObjCMessageExpr(E).getComplexVal();
   }
   ComplexPairTy VisitArraySubscriptExpr(Expr *E) { return EmitLoadOfLValue(E); }
-  ComplexPairTy VisitMemberExpr(const Expr *E) { return EmitLoadOfLValue(E); }
+  ComplexPairTy VisitMemberExpr(MemberExpr *ME) {
+    if (CodeGenFunction::ConstantEmission Constant =
+            CGF.tryEmitAsConstant(ME)) {
+      CGF.EmitIgnoredExpr(ME->getBase());
+      return emitConstant(Constant, ME);
+    }
+    return EmitLoadOfLValue(ME);
+  }
   ComplexPairTy VisitOpaqueValueExpr(OpaqueValueExpr *E) {
     if (E->isGLValue())
       return EmitLoadOfLValue(CGF.getOpaqueLValueMapping(E), E->getExprLoc());
diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index 1170b01..46a01a3 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -428,14 +428,19 @@
     return CGF.getOpaqueRValueMapping(E).getScalarVal();
   }
 
+  Value *emitConstant(const CodeGenFunction::ConstantEmission &Constant,
+                      Expr *E) {
+    assert(Constant && "not a constant");
+    if (Constant.isReference())
+      return EmitLoadOfLValue(Constant.getReferenceLValue(CGF, E),
+                              E->getExprLoc());
+    return Constant.getValue();
+  }
+
   // l-values.
   Value *VisitDeclRefExpr(DeclRefExpr *E) {
-    if (CodeGenFunction::ConstantEmission result = CGF.tryEmitAsConstant(E)) {
-      if (result.isReference())
-        return EmitLoadOfLValue(result.getReferenceLValue(CGF, E),
-                                E->getExprLoc());
-      return result.getValue();
-    }
+    if (CodeGenFunction::ConstantEmission Constant = CGF.tryEmitAsConstant(E))
+      return emitConstant(Constant, E);
     return EmitLoadOfLValue(E);
   }
 
@@ -1299,13 +1304,15 @@
 }
 
 Value *ScalarExprEmitter::VisitMemberExpr(MemberExpr *E) {
-  llvm::APSInt Value;
-  if (E->EvaluateAsInt(Value, CGF.getContext(), Expr::SE_AllowSideEffects)) {
-    if (E->isArrow())
-      CGF.EmitScalarExpr(E->getBase());
-    else
-      EmitLValue(E->getBase());
-    return Builder.getInt(Value);
+  if (CodeGenFunction::ConstantEmission Constant = CGF.tryEmitAsConstant(E)) {
+    CGF.EmitIgnoredExpr(E->getBase());
+    return emitConstant(Constant, E);
+  } else {
+    llvm::APSInt Value;
+    if (E->EvaluateAsInt(Value, CGF.getContext(), Expr::SE_AllowSideEffects)) {
+      CGF.EmitIgnoredExpr(E->getBase());
+      return Builder.getInt(Value);
+    }
   }
 
   return EmitLoadOfLValue(E);
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index a8c3064..77712cf 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -3158,6 +3158,7 @@
   };
 
   ConstantEmission tryEmitAsConstant(DeclRefExpr *refExpr);
+  ConstantEmission tryEmitAsConstant(const MemberExpr *ME);
 
   RValue EmitPseudoObjectRValue(const PseudoObjectExpr *e,
                                 AggValueSlot slot = AggValueSlot::ignored());
diff --git a/lib/Sema/SemaExprObjC.cpp b/lib/Sema/SemaExprObjC.cpp
index 28581ba..83ef799 100644
--- a/lib/Sema/SemaExprObjC.cpp
+++ b/lib/Sema/SemaExprObjC.cpp
@@ -2705,6 +2705,9 @@
     }
   }
 
+  if (ReceiverType->isObjCIdType() && !isImplicit)
+    Diag(Receiver->getExprLoc(), diag::warn_messaging_unqualified_id);
+
   // There's a somewhat weird interaction here where we assume that we
   // won't actually have a method unless we also don't need to do some
   // of the more detailed type-checking on the receiver.
diff --git a/test/CodeGenCXX/member-expr-references-variable.cpp b/test/CodeGenCXX/member-expr-references-variable.cpp
new file mode 100644
index 0000000..8c1dded
--- /dev/null
+++ b/test/CodeGenCXX/member-expr-references-variable.cpp
@@ -0,0 +1,104 @@
+// RUN: %clang_cc1 -std=c++11 %s -triple x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s
+
+struct Agg { const char * x; const char * y; constexpr Agg() : x(0), y(0) {} };
+
+struct Struct {
+   constexpr static const char *name = "foo";
+
+   constexpr static __complex float complexValue = 42.0;
+
+   static constexpr const Agg &agg = Agg();
+
+   Struct();
+   Struct(int x);
+};
+
+void use(int n, const char *c);
+
+Struct *getPtr();
+
+// CHECK: @[[STR:.*]] = private unnamed_addr constant [4 x i8] c"foo\00", align 1
+
+void scalarStaticVariableInMemberExpr(Struct *ptr, Struct &ref) {
+  use(1, Struct::name);
+// CHECK: call void @_Z3useiPKc(i32 1, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @[[STR]], i32 0, i32 0))
+  Struct s;
+  use(2, s.name);
+// CHECK: call void @_Z3useiPKc(i32 2, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @[[STR]], i32 0, i32 0))
+  use(3, ptr->name);
+// CHECK: load %struct.Struct*, %struct.Struct** %{{.*}}, align 8
+// CHECK: call void @_Z3useiPKc(i32 3, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @[[STR]], i32 0, i32 0))
+  use(4, ref.name);
+// CHECK: load %struct.Struct*, %struct.Struct** %{{.*}}, align 8
+// CHECK: call void @_Z3useiPKc(i32 4, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @[[STR]], i32 0, i32 0))
+  use(5, Struct(2).name);
+// CHECK: call void @_ZN6StructC1Ei(%struct.Struct* %{{.*}}, i32 2)
+// CHECK: call void @_Z3useiPKc(i32 5, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @[[STR]], i32 0, i32 0))
+  use(6, getPtr()->name);
+// CHECK: call %struct.Struct* @_Z6getPtrv()
+// CHECK: call void @_Z3useiPKc(i32 6, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @[[STR]], i32 0, i32 0))
+}
+
+void use(int n, __complex float v);
+
+void complexStaticVariableInMemberExpr(Struct *ptr, Struct &ref) {
+  use(1, Struct::complexValue);
+// CHECK: store float 4.200000e+01, float* %[[coerce0:.*]].{{.*}}, align 4
+// CHECK: store float 0.000000e+00, float* %[[coerce0]].{{.*}}, align 4
+// CHECK: %[[cast0:.*]] = bitcast { float, float }* %[[coerce0]] to <2 x float>*
+// CHECK: %[[vector0:.*]] = load <2 x float>, <2 x float>* %[[cast0]], align 4
+// CHECK: call void @_Z3useiCf(i32 1, <2 x float> %[[vector0]])
+  Struct s;
+  use(2, s.complexValue);
+// CHECK: store float 4.200000e+01, float* %[[coerce1:.*]].{{.*}}, align 4
+// CHECK: store float 0.000000e+00, float* %[[coerce1]].{{.*}}, align 4
+// CHECK: %[[cast1:.*]] = bitcast { float, float }* %[[coerce1]] to <2 x float>*
+// CHECK: %[[vector1:.*]] = load <2 x float>, <2 x float>* %[[cast1]], align 4
+// CHECK: call void @_Z3useiCf(i32 2, <2 x float> %[[vector1]])
+  use(3, ptr->complexValue);
+// CHECK: load %struct.Struct*, %struct.Struct** %{{.*}}, align 8
+// CHECK: store float 4.200000e+01, float* %[[coerce2:.*]].{{.*}}, align 4
+// CHECK: store float 0.000000e+00, float* %[[coerce2]].{{.*}}, align 4
+// CHECK: %[[cast2:.*]] = bitcast { float, float }* %[[coerce2]] to <2 x float>*
+// CHECK: %[[vector2:.*]] = load <2 x float>, <2 x float>* %[[cast2]], align 4
+// CHECK: call void @_Z3useiCf(i32 3, <2 x float> %[[vector2]])
+  use(4, ref.complexValue);
+// CHECK: load %struct.Struct*, %struct.Struct** %{{.*}}, align 8
+// CHECK: store float 4.200000e+01, float* %[[coerce3:.*]].{{.*}}, align 4
+// CHECK: store float 0.000000e+00, float* %[[coerce3]].{{.*}}, align 4
+// CHECK: %[[cast3:.*]] = bitcast { float, float }* %[[coerce3]] to <2 x float>*
+// CHECK: %[[vector3:.*]] = load <2 x float>, <2 x float>* %[[cast3]], align 4
+// CHECK: call void @_Z3useiCf(i32 4, <2 x float> %[[vector3]])
+  use(5, Struct(2).complexValue);
+// CHECK: call void @_ZN6StructC1Ei(%struct.Struct* %{{.*}}, i32 2)
+// CHECK: store float 4.200000e+01, float* %[[coerce4:.*]].{{.*}}, align 4
+// CHECK: store float 0.000000e+00, float* %[[coerce4]].{{.*}}, align 4
+// CHECK: %[[cast4:.*]] = bitcast { float, float }* %[[coerce4]] to <2 x float>*
+// CHECK: %[[vector4:.*]] = load <2 x float>, <2 x float>* %[[cast4]], align 4
+// CHECK: call void @_Z3useiCf(i32 5, <2 x float> %[[vector4]])
+  use(6, getPtr()->complexValue);
+// CHECK: call %struct.Struct* @_Z6getPtrv()
+// CHECK: store float 4.200000e+01, float* %[[coerce5:.*]].{{.*}}, align 4
+// CHECK: store float 0.000000e+00, float* %[[coerce5]].{{.*}}, align 4
+// CHECK: %[[cast5:.*]] = bitcast { float, float }* %[[coerce5]] to <2 x float>*
+// CHECK: %[[vector5:.*]] = load <2 x float>, <2 x float>* %[[cast5]], align 4
+// CHECK: call void @_Z3useiCf(i32 6, <2 x float> %[[vector5]])
+}
+
+void aggregateRefInMemberExpr(Struct *ptr, Struct &ref) {
+  use(1, Struct::agg.x);
+// CHECK: %[[value0:.*]] = load i8*, i8** getelementptr inbounds (%struct.Agg, %struct.Agg* @_ZGRN6Struct3aggE_, i32 0, i32 0), align 8
+// CHECK: call void @_Z3useiPKc(i32 1, i8* %[[value0]])
+  Struct s;
+  use(2, s.agg.x);
+// CHECK: %[[value1:.*]] = load i8*, i8** getelementptr inbounds (%struct.Agg, %struct.Agg* @_ZGRN6Struct3aggE_, i32 0, i32 0), align 8
+// CHECK: call void @_Z3useiPKc(i32 2, i8* %[[value1]])
+  use(3, ptr->agg.x);
+// CHECK: load %struct.Struct*, %struct.Struct** %{{.*}}, align 8
+// CHECK: %[[value2:.*]] = load i8*, i8** getelementptr inbounds (%struct.Agg, %struct.Agg* @_ZGRN6Struct3aggE_, i32 0, i32 0), align 8
+// CHECK: call void @_Z3useiPKc(i32 3, i8* %[[value2]])
+  use(4, ref.agg.x);
+// CHECK: load %struct.Struct*, %struct.Struct** %{{.*}}, align 8
+// CHECK: %[[value3:.*]] = load i8*, i8** getelementptr inbounds (%struct.Agg, %struct.Agg* @_ZGRN6Struct3aggE_, i32 0, i32 0), align 8
+// CHECK: call void @_Z3useiPKc(i32 4, i8* %[[value3]])
+}
diff --git a/test/SemaObjC/warn-messaging-id.mm b/test/SemaObjC/warn-messaging-id.mm
new file mode 100644
index 0000000..8112cfa
--- /dev/null
+++ b/test/SemaObjC/warn-messaging-id.mm
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wno-objc-root-class -Wobjc-messaging-id %s
+
+@interface CallMeMaybe
+
+- (void)doThing:(int)intThing;
+
+@property int thing;
+
+@end
+
+template<typename T>
+void instantiate(const T &x) {
+  [x setThing: 22]; // expected-warning {{messaging unqualified id}}
+}
+
+void fn() {
+  id myObject;
+  [myObject doThing: 10]; // expected-warning {{messaging unqualified id}}
+  [myObject setThing: 11]; // expected-warning {{messaging unqualified id}}
+  instantiate(myObject); // expected-note {{in instantiation}}
+}