object allocation

[Henry Cejtin]

The  trick  I  guess  is  really that the pointer that you use is to the last
value stored.  Thus you save one add.

The point is that the frontier starts out at one  end.   When  you  are  done
initializing,  some register will point to the other end.  (The increments of
the register space cost is exactly offset by the saving of 1 byte because you
don't  need  an  offset  in the store.)  Thus you can save an add if the last
location stored is what you use as the value.