Use native behavior for dead code elimination

pkg/compiler/lib/src/ssa/optimize.dart

 // Copyright (c) 2012, 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.
 
 part of ssa;
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
@@ skipping 986 matching lines @@
       ConstantValue constant =
           new DummyConstantValue(const TypeMask.nonNullEmpty());
       zapInstructionCache = analyzer.graph.addConstant(constant, compiler);
     }
     return zapInstructionCache;
   }
 
   /// Returns true of [foreign] will throw an noSuchMethod error if
   /// receiver is `null` before having any other side-effects.
   bool templateThrowsNSMonNull(HForeignCode foreign, HInstruction receiver) {
+    if (foreign.inputs.length < 1) return false;
+    if (foreign.inputs.first != receiver) return false;
+    if (foreign.throwBehavior.isNullNSMGuard) return true;
+
+    // TODO(sra): Fix NativeThrowBehavior to distinguish MAY from
+    // throws-nsm-on-null-followed-by-MAY and remove all the code below.
+
     // We look for a template of the form
     //
     // #.something -or- #.something()
     //
     // where # is substituted by receiver.
     js.Template template = foreign.codeTemplate;
     js.Node node = template.ast;
     // #.something = ...
     if (node is js.Assignment) {
       js.Assignment assignment = node;
       node = assignment.leftHandSide;
     }
 
     // #.something
     if (node is js.PropertyAccess) {
       js.PropertyAccess access = node;
       if (access.receiver is js.InterpolatedExpression) {
         js.InterpolatedExpression hole = access.receiver;
-        return hole.isPositional && foreign.inputs.first == receiver;
+        return hole.isPositional && hole.nameOrPosition == 0;
       }
     }
     return false;
   }
 
   /// Returns whether the next throwing instruction that may have side
   /// effects after [instruction], throws [NoSuchMethodError] on the
   /// same receiver of [instruction].
   bool hasFollowingThrowingNSM(HInstruction instruction) {
     HInstruction receiver = instruction.getDartReceiver(compiler);
@@ skipping 1200 matching lines @@
 
     keyedValues.forEach((receiver, values) {
       result.keyedValues[receiver] =
           new Map<HInstruction, HInstruction>.from(values);
     });
 
     result.nonEscapingReceivers.addAll(nonEscapingReceivers);
     return result;
   }
 }