Revert r31326.

runtime/vm/flow_graph_optimizer.cc

 // 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.
 
 #include "vm/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 4942 matching lines @@
   // this value is stored in a field, escapes to another function or
   // participates in a phi.
   static bool CanBeAliased(AllocateObjectInstr* alloc) {
     if (alloc->identity() == AllocateObjectInstr::kUnknown) {
       bool escapes = false;
       for (Value* use = alloc->input_use_list();
            use != NULL;
            use = use->next_use()) {
         Instruction* instr = use->instruction();
         if (instr->IsPushArgument() ||
-            (instr->IsStoreVMField()
-             && (use->use_index() != StoreVMFieldInstr::kObjectPos)) ||
-            (instr->IsStoreInstanceField()
-             && (use->use_index() != StoreInstanceFieldInstr::kInstancePos)) ||
+            (instr->IsStoreVMField() && (use->use_index() != 1)) ||
+            (instr->IsStoreInstanceField() && (use->use_index() != 0)) ||
             instr->IsStoreStaticField() ||
             instr->IsPhi() ||
             instr->IsAssertAssignable() ||
             instr->IsRedefinition()) {
           escapes = true;
           break;
         }
       }
 
       alloc->set_identity(escapes ? AllocateObjectInstr::kAliased
@@ skipping 3171 matching lines @@
   }
 
   // Insert materializations at environment uses.
   for (intptr_t i = 0; i < exits.length(); i++) {
     CreateMaterializationAt(exits[i], alloc, alloc->cls(), *fields);
   }
 }
 
 
 }  // namespace dart