dart2js cps: More aggressive operator specialization.

pkg/compiler/lib/src/cps_ir/gvn.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.cps_ir.gvn;
 
 import 'cps_ir_nodes.dart';
 import '../universe/side_effects.dart';
 import '../elements/elements.dart';
 import 'optimizers.dart' show Pass;
@@ skipping 174 matching lines @@
       if (node is LetCont) {
         continue;
       }
       return false;
     }
     return node == currentLoopHeader;
   }
 
   bool isHoistablePrimitive(Primitive prim) {
     if (prim.isSafeForElimination) return true;
-    if (prim is NullCheck ||
+    if (prim is ReceiverCheck ||
         prim is BoundsCheck ||
         prim is GetLength ||
         prim is GetField ||
         prim is GetIndex) {
       // Expressions that potentially throw but have no other effects can be
       // hoisted if they occur as the first impure expression in a loop.
       // Note regarding BoundsCheck: the current array length is an input to
       // check, so the check itself has no heap dependency.  It will only be
       // hoisted if the length was hoisted.
       // TODO(asgerf): In general we could hoist these out of multiple loops,
@@ skipping 554 matching lines @@
 
   @override
   processReference(Reference ref) {
     callback(ref);
   }
 
   static void forEach(Primitive node, ReferenceCallback callback) {
     new InputVisitor(callback).visit(node);
   }
 }