After a dynamic call, refine the receiver type by looking at the potential targets of that call.

sdk/lib/_internal/compiler/implementation/ssa/tracer.dart

 // Copyright (c) 2013, 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 tracer;
 
 import 'dart:async' show EventSink;
 
 import 'ssa.dart';
 import '../js_backend/js_backend.dart';
@@ skipping 65 matching lines @@
 
   void addInstructions(HInstructionStringifier stringifier,
                        HInstructionList list) {
     for (HInstruction instruction = list.first;
          instruction != null;
          instruction = instruction.next) {
       int bci = 0;
       int uses = instruction.usedBy.length;
       String changes = instruction.hasSideEffects() ? '!' : ' ';
       String depends = instruction.dependsOnSomething() ? '?' : '';
+      String usesGvn = instruction.useGvn() ? 'G' : '';
       addIndent();
       String temporaryId = stringifier.temporaryId(instruction);
       String instructionString = stringifier.visit(instruction);
-      add("$bci $uses $temporaryId $instructionString $changes $depends <|@\n");
+      add("$bci $uses $temporaryId $instructionString "
+          "$changes $depends $usesGvn <|@\n");
     }
   }
 
   void visitBasicBlock(HBasicBlock block) {
     HInstructionStringifier stringifier =
         new HInstructionStringifier(context, block);
     assert(block.id != null);
     tag("block", () {
       printProperty("name", "B${block.id}");
       printProperty("from_bci", -1);
@@ skipping 449 matching lines @@
 
   String visitTypeConversion(HTypeConversion node) {
     return "TypeConversion: ${temporaryId(node.checkedInput)} to "
       "${node.instructionType}";
   }
 
   String visitRangeConversion(HRangeConversion node) {
     return "RangeConversion: ${node.checkedInput}";
   }
 }