G'day all.
On Sat, Apr 27, 2002 at 07:00:17AM +0100, Piers Cawley wrote:
> I'm trying to see how, if you want genuine continuations and/or tail
> call optimization, you're going to get away with anything but 'caller
> saves everything important to it', and what do you know, I
> can't.
If you have genuine continuations, you don't put anything important in
registers across a call to a continuation. In fact, usually you don't
need to.
I don't see what the problem is with tail call optimization. The
simplest form of tail call optimization is that you jump instead
of bsr and use the caller's ret to return to your caller. When you
get more complex, you emulate the callee's prologue and then just
jump to the point after the prologue. In Parrot, subs are meant
to have only One True Entry Point, so you'd probably do it with a
wrapper sub:
foo:
sub_prologue_for_foo
tailcall foo_TAIL
foo_TAIL:
do_whatever
sub_epilogue_for_foo
ret
Callees who are aware of the tailcall entry for foo can use it,
otherwise they can use the non-optimized version.
Cheers,
Andrew Bromage
