Sujet : Re: Decrement And Branch
De : ldo (at) *nospam* nz.invalid (Lawrence D'Oliveiro)
Groupes : comp.archDate : 14. Aug 2024, 00:00:12
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <v9gl1b$30as$7@dont-email.me>
References : 1
User-Agent : Pan/0.159 (Vovchansk; )
On Tue, 13 Aug 2024 09:00:25 -0000 (UTC), I wrote:
However, the good old VAX (in
its usual kitchen-sink fashion) had a whole set of variations, including
one that decremented down to -1 instead of zero. And the Motorola 68000
family only had the decrement down to -1 version.
VAX example of how to use SOBGEQ instead of SOBGTR:
movl «loop count», Rn
br bottom_of_loop
top_of_loop:
.... body of loop ...
bottom_of_loop:
sobgeq Rn, top_of_loop
Like I said, I wondered why this sort of thing wasn’t more common ...
Decrement And Branch
Re: Decrement And Branch