From: user5857@newsgrouper.org.invalid
Stephen Fuld posted:
> On 11/4/2025 11:15 AM, MitchAlsup wrote:
> >
> > anton@mips.complang.tuwien.ac.at (Anton Ertl) posted:
> >
> >> Thomas Koenig writes:
> >>> Should be possible. A question is if you want to have a special
> >>> register for that (like POWER's link register),
> >>
> >> There is this idea of splitting an (indirect) branch into a
> >> prepare-to-branch instruction and a take-branch instruction. The
> >
> > I first heard about this 1982 from Burton Smith.
> >
> >> prepare-to-branch instruction announces the branch target to the CPU,
> >> and Power's mtlr and mtctr are examples of that (somewhat muddled by
> >> the fact that the ctr register can also be used for counted loops as
> >> well as for indirect branches), and IA-64's branch-target registers
> >> and the instructions that move there are another example. AFAIK SPARC
> >> acquired something in this direction (touted as good for accelerating
> >> Java) in the early 2000s. The take-branch instruction on Power is
> >> blr/bctr.
> >>
> >> I used to think that this kind of splitting is a good idea, and it is
> >> certainly better than a branch-delay slot or a branch with a fixed
> >> number of delay slots.
> >
> > PL/1 allows for Label variables so one can build their own
> > switches (and state machines with variable paths). I used
> > these in a checkers playing program 1974.
>
> Wasn't this PL/1 feature "inherited" from the, now rightly deprecated,
> Alter/Goto in COBOL and Assigned GOTO in Fortran?
Probably.
I find it somewhat amusing that modern languages moved away from
label variables and into method calls -- which if you look at it
from 5,000 feet/metres -- is just a more expensive "label".
I also find it amusing that the backbone of modern software is
a static version of label variables -- we call them switch state-
ments.
But you can be sure COBOL got them from assembly language programmers.
>
>
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
