Improve dead code elimination by transitively marking live code and removing all dead code. Replace…

src/hydrogen.h

Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index 8df7a297269fb1000e7ed8eacc5fbcb58fbbd2ea..860ac9f04e4f7bdd7b0e0bcf4c251b0f55a0072f 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -277,17 +277,17 @@ class HGraph: public ZoneObject {
   void GlobalValueNumbering();
   bool ProcessArgumentsObject();
   void EliminateRedundantPhis();
-  void EliminateUnreachablePhis();
   void Canonicalize();
   void OrderBlocks();
   void AssignDominators();
   void SetupInformativeDefinitions();
   void EliminateRedundantBoundsChecks();
   void DehoistSimpleArrayIndexComputations();
-  void DeadCodeElimination();
   void RestoreActualValues();
+  void MarkNotDead(HValue* ref, HValue* instr, ZoneList<HValue*>* worklist);
+  bool TryDeadCodeElimination(HValue *instr);
+  void DeadCodeElimination();
   void PropagateDeoptimizingMark();
-  void EliminateUnusedInstructions();
 
   // Returns false if there are phi-uses of the arguments-object
   // which are not supported by the optimizing compiler.