Use a separate marker value to allocate the arguments object on deoptimzation...

src/objects.h

 // Copyright 2010 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 575 matching lines @@
 template <class C> static inline bool Is(Object* obj);
 
 
 class MaybeObject BASE_EMBEDDED {
  public:
   inline bool IsFailure();
   inline bool IsRetryAfterGC();
   inline bool IsOutOfMemory();
   inline bool IsException();
   INLINE(bool IsTheHole());
+  INLINE(bool IsArgumentsMarker());

[Kevin Millikin (Chromium), 2011/01/06 14:00:47]

I wonder why we INLINE exactly these two?

[fschneider, 2011/01/06 16:22:49]

Good question. I don't know. Maybe we should use INLINE for the others too.

   inline bool ToObject(Object** obj) {
     if (IsFailure()) return false;
     *obj = reinterpret_cast<Object*>(this);
     return true;
   }
   inline Object* ToObjectUnchecked() {
     ASSERT(!IsFailure());
     return reinterpret_cast<Object*>(this);
   }
   inline Object* ToObjectChecked() {
@@ skipping 5783 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_