Reenable GVN for fields.

lib/compiler/implementation/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.
 
 interface OptimizationPhase {
   String get name();
   void visitGraph(HGraph graph);
 }
 
 class SsaOptimizerTask extends CompilerTask {
@@ skipping 981 matching lines @@
     List<HBasicBlock> predecessors = dominated.predecessors;
     for (int i = 0, length = predecessors.length; i < length; i++) {
       HBasicBlock block = predecessors[i];
       int id = block.id;
       // If the current predecessor block is on the path from the
       // dominator to the dominated, it must have an id that is in the
       // range from the dominator to the dominated.
       if (dominator.id < id && id < dominated.id && !visited.contains(id)) {
         visited.add(id);
         changesFlags |= blockChangesFlags[id];
+        // Loop bodies might not be on the path from dominator to dominated,
+        // but they can invalidate values.
+        changesFlags |= loopChangesFlags[id];
         changesFlags |= getChangesFlagsForDominatedBlock(dominator, block);
       }
     }
     return changesFlags;
   }
 }
 
 // This phase merges equivalent instructions on different paths into
 // one instruction in a dominator block. It runs through the graph
 // post dominator order and computes a ValueSet for each block of
@@ skipping 294 matching lines @@
       // this type for the field is still a strong signal
       // indicating the expected type of the field.
       field.propagatedType = type;
     } else {
       // If there are no invoked setters we know the type of
       // this field for sure.
       field.guaranteedType = type;
     }
   }
 }