More general dead phi elimination.

runtime/vm/flow_graph.h

 // 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.
 
 #ifndef VM_FLOW_GRAPH_H_
 #define VM_FLOW_GRAPH_H_
 
 #include "vm/growable_array.h"
 #include "vm/intermediate_language.h"
 #include "vm/parser.h"
@@ skipping 203 matching lines @@
                                  const Field* field);
 
   ZoneGrowableArray<const Field*>* guarded_fields() const {
     return guarded_fields_;
   }
 
  private:
   friend class IfConverter;
   friend class BranchSimplifier;
   friend class ConstantPropagator;
+  friend class DeadCodeElimination;
 
   // SSA transformation methods and fields.
   void ComputeDominators(GrowableArray<BitVector*>* dominance_frontier);
 
   void CompressPath(
       intptr_t start_index,
       intptr_t current_index,
       GrowableArray<intptr_t>* parent,
       GrowableArray<intptr_t>* label);
 
@@ skipping 157 matching lines @@
   // Per block sets of available blocks. Block A is available at the block B if
   // and only if A dominates B and all paths from A to B are free of side
   // effects.
   GrowableArray<BitVector*> available_at_;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_H_