[Gambas-user] Gambas has Gosub now!

[Benoît Minisini]

Le 09/07/2012 00:13, Emil Lenngren a écrit :
> I have a little optimization idea:
>
> Instead of allocating a new array EVERY time a gosub is called, instead use
> the normal gambas stack.
> First, let GP represent the offset 0 in &BP[fp->n_local + fp->n_ctrl].
>
> At a gosub, run STACK_check(1 + fp->stack_usage - fp->n_local), then the
> return address and ctrl values are stored on the stack starting at
> &BP[fp->n_local + fp->n_ctrl + GP], then GP and SP is added by 1 +
> fp->n_ctrl.
>
> On a gosub return, if GP == 0, it is a normal return. If not, it is a gosub
> return. Then first subtract 1 + fp->n_ctrl from GP and SP and restore the
> ctrl values and PC.
>
> At exception handling, going to a Catch, change
> while (SP > (BP + FP->n_local + FP->n_ctrl))
> to
> while (SP > (BP + FP->n_local + FP->n_ctrl + GP))
>
> I think there is nothing else that has to be done. Leaving a function pops
> off the stack until it reaches PP, so that is fine.
>
> It is also possible to completely remove the function
> STACK_free_gosub_stack.
>
> Can this be a good idea?
>
> /Emil
>

Yes! But I must think a bit about it.

For example, any stack slot can be sent to RELEASE(), so something must 
be done if we have to store the value of PC in the stack. But it should 
not be too difficult...

-- 
Benoît Minisini