Remove variable rewrites and the unneccesary Slot class.

src/hydrogen.h

 // Copyright 2011 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 437 matching lines @@
   // True if index is included in the expression stack part of the environment.
   bool HasExpressionAt(int index) const;
 
   void Initialize(int parameter_count, int local_count, int stack_height);
   void Initialize(const HEnvironment* other);
 
   // Map a variable to an environment index.  Parameter indices are shifted
   // by 1 (receiver is parameter index -1 but environment index 0).
   // Stack-allocated local indices are shifted by the number of parameters.
   int IndexFor(Variable* variable) const {
-    Slot* slot = variable->AsSlot();
-    ASSERT(slot != NULL && slot->IsStackAllocated());
-    int shift = (slot->type() == Slot::PARAMETER)
+    ASSERT(variable->IsStackAllocated());
+    int shift = variable->IsParameter()
         ? 1
         : parameter_count_ + specials_count_;
-    return slot->index() + shift;
+    return variable->index() + shift;
   }
 
   Handle<JSFunction> closure_;
   // Value array [parameters] [specials] [locals] [temporaries].
   ZoneList<HValue*> values_;
   ZoneList<int> assigned_variables_;
   int parameter_count_;
   int specials_count_;
   int local_count_;
   HEnvironment* outer_;
@@ skipping 759 matching lines @@
   const char* filename_;
   HeapStringAllocator string_allocator_;
   StringStream trace_;
   int indent_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_H_