Piers Cawley <[EMAIL PROTECTED]> wrote:
> The thing is, 'pushtop' is almost certainly the wrong thing to do. You
> should only push the registers you care about onto the register
> stacks.
Yes:
$ time parrot -j oofib.imc
fib(28) = 317811 3.050051s
real 0m3.077s
$ time parrot -j -Oc oofib.imc
fib(28) = 317811 2.234049s
real 0m2.262s
C<savetop> becomes C<pushtopp> if only P-registers are used. Saving only
3 or 5 registers isn't possible yet. We have no opcodes for that.
> The catch is that, whilst I know which registers *I* care about, I don't
> know which registers IMCC cares about. So maybe IMCC's 'newcont' should
> expand to:
> save 'imcc_magic_register1'
> save 'imcc_magic_register2'
> target = newsub .Continuation, dest
> restore 'imcc_magic_register2'
> restore 'imcc_magic_register1'
> Notice how making a continuation looks remarkably like making a function
> call.
The usage of above Continuation would be to pass it on into a subroutine
and eventually return through it to an alternate position? If yes, then
the Continuation should be created inside the call sequence to avoid
duplicate register saving and restoring code:
res = subroutine(args, NEWCONT)
But that's only one side of the business. The code at the return label
C<dest>) has to restore the same registers too.
If the target of the Continuation isn't the function return, it has to
look somethin like this:
goto around_cont_ret
cont_ret_target:
restoretop # or whatever was saved
around_cont_ret:
> If the destination of the continuation is within the current
> compilation unit (which it probably should be, or things get *very*
> weird) then, potentially, IMCC knows what registers the continuation
> target cares about and can automagically save the current .locals as
> well.
Yes.
> Would it be possible to arrange things so that
> $P0 = new .Continuation
> $P0 = P1 # The current RetContinuation
> makes $P0 into a full continuation equivalent to the RetContinuation?
Sure. It depends on what part of the context should be copied into the
Continuation:
get_addr Idest, P1
set_addr $P0, Idest # assign dest - implemented
or
assign $P0, P1 # vtable->set_pmc (N/Y)
which could do whatever is appropriate.
($P0 = P1 just aliases the two and isn't usable for assignment)
leo
