Ensure that allocation sinking candidates are classified as not-aliased before final load forwardin…

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/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
@@ skipping 6404 matching lines @@
        !block_it.Done();
        block_it.Advance()) {
     BlockEntryInstr* block = block_it.Current();
     for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
       AllocateObjectInstr* alloc = it.Current()->AsAllocateObject();
       if ((alloc != NULL) && IsAllocationSinkingCandidate(alloc)) {
         if (FLAG_trace_optimization) {
           OS::Print("discovered allocation sinking candidate: v%"Pd"\n",
                     alloc->ssa_temp_index());
         }
+
+        if (alloc->identity() == AllocateObjectInstr::kAliased) {
+          // Allocation might have been classified as aliased earlier due to
+          // some operations that are now eliminated.
+          alloc->set_identity(AllocateObjectInstr::kNotAliased);
+        }
+
         candidates.Add(alloc);
       }
     }
   }
 
   // Insert MaterializeObject instructions that will describe the state of the
   // object at all deoptimization points. Each inserted materialization looks
   // like this (where v_0 is allocation that we are going to eliminate):
   //   v_1     <- LoadField(v_0, field_1)
   //           ...
@@ skipping 136 matching lines @@
 
   // Insert materializations at environment uses.
   const Class& cls = Class::Handle(alloc->constructor().Owner());
   for (intptr_t i = 0; i < exits.length(); i++) {
     CreateMaterializationAt(exits[i], alloc, cls, *fields);
   }
 }
 
 
 }  // namespace dart