Re: byte-code optimizations

[Stefan]

> +         ;; dup varbind-X [car/cdr ...] unbind-1 --> [car/cdr ...]

I get the same optimization result by adding

        car/cdr/equal/nth unbind --> unbind car/cdr/equal/nth

Problem is that such an optimization is only safe if car/cdr/... is not
affected by the bound thing.  If the `unbind' unbinds a variable, then
I think it's always safe.  So I've added to the lapcode optimizer some logic
to keep track of the specpdl stack so that I can distinguish an unbind that
terminates a varbind from one that terminates an unwind-protect.

Better yet: you also get the exact same result code (without any lapcode
optimization) if you use

   (defsubst* cddr (x) (cdr (cdr x)))

I.e. using the `defubst*' (from CL).


        Stefan