dart2js cps: More aggressive operator specialization.

pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart

 // Copyright (c) 2014, 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 tree_ir_builder;
 
 import '../common.dart';
 import '../constants/values.dart';
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
 import '../elements/elements.dart';
@@ skipping 681 matching lines @@
             node.codeTemplate,
             node.type,
             arguments,
             node.nativeBehavior,
             nullableArguments,
             node.dependency);
       };
     }
   }
 
-  visitNullCheck(cps_ir.NullCheck node) => (Statement next) {
-    return new NullCheck(
+  visitReceiverCheck(cps_ir.ReceiverCheck node) => (Statement next) {
+    // The CPS IR uses 'isNullCheck' because the semantics are important.
+    // In the Tree IR, syntax is more important, so the receiver check uses
+    // "useInvoke" to denote if an invocation should be emitted.
+    return new ReceiverCheck(
         condition: getVariableUseOrNull(node.condition),
         value: getVariableUse(node.value),
         selector: node.selector,
         useSelector: node.useSelector,
+        useInvoke: !node.isNullCheck,
         next: next,
         sourceInformation: node.sourceInformation);
   };
 
   Expression visitGetLazyStatic(cps_ir.GetLazyStatic node) {
     return new GetStatic.lazy(node.element, node.sourceInformation);
   }
 
   @override
   NodeCallback visitYield(cps_ir.Yield node) {
@@ skipping 20 matching lines @@
 
   visitFunctionDefinition(cps_ir.FunctionDefinition node) {
     unexpectedNode(node);
   }
   visitParameter(cps_ir.Parameter node) => unexpectedNode(node);
   visitContinuation(cps_ir.Continuation node) => unexpectedNode(node);
   visitMutableVariable(cps_ir.MutableVariable node) => unexpectedNode(node);
   visitRethrow(cps_ir.Rethrow node) => unexpectedNode(node);
   visitBoundsCheck(cps_ir.BoundsCheck node) => unexpectedNode(node);
 }