First implementation of store elimination.

src/hydrogen-instructions.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 1229 matching lines @@
   }
 
   bool CanTruncateToInt32() const { return CheckFlag(kTruncatingToInt32); }
 
   virtual LInstruction* CompileToLithium(LChunkBuilder* builder) = 0;
 
 #ifdef DEBUG
   virtual void Verify() V8_OVERRIDE;
 #endif
 
+  bool CanDeoptimize();
+
   virtual bool HasStackCheck() { return false; }
 
   DECLARE_ABSTRACT_INSTRUCTION(Instruction)
 
  protected:
   HInstruction(HType type = HType::Tagged())
       : HValue(type),
         next_(NULL),
         previous_(NULL),
         position_(RelocInfo::kNoPosition) {
@@ skipping 6120 matching lines @@
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_