Added a simple dead code removal phase.

src/hydrogen.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 250 matching lines @@
   void ComputeSafeUint32Operations();
   bool ProcessArgumentsObject();
   void EliminateRedundantPhis();
   void EliminateUnreachablePhis();
   void Canonicalize();
   void OrderBlocks();
   void AssignDominators();
   void ReplaceCheckedValues();
   void EliminateRedundantBoundsChecks();
   void DehoistSimpleArrayIndexComputations();
+  void DeadCodeElimination();
   void PropagateDeoptimizingMark();
 
   // Returns false if there are phi-uses of the arguments-object
   // which are not supported by the optimizing compiler.
   bool CheckArgumentsPhiUses();
 
   // Returns false if there are phi-uses of an uninitialized const
   // which are not supported by the optimizing compiler.
   bool CheckConstPhiUses();
 
@@ skipping 1205 matching lines @@
   const char* filename_;
   HeapStringAllocator string_allocator_;
   StringStream trace_;
   int indent_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_H_