From: daniel pralle (daniel.pralle_at_stud.uni-hannover.de)
Date: 2001-06-25 13:54:02
On Sun, 24 Jun 2001, groepaz wrote: > - replacing sequences of register-shifts by hash-table-accesses (need > one index register, so may be used after peephole analyzing) eg: > > replace: > > lda something > lsr a > lsr a > lsr a > lsr a > sta something > > by: > ldx something > lda lsr4tab,x > sta something > > ...saving some cycles (and memory if used often enough to compensate > the tablesize) Aha! you are saving THREE-cycles. We are so little on registers that we always, me at least, need every-REgister busy. therefor saving/restoring the INDEX-Reg. 3+3 cycles. So we are THREE-cycles MINUS! as far as I had experienced the SHIFT-things is the LAST thing to optimize. If you have more than FOUR shifts, like in your example, you shift the the other way round: replace: lda zp lsr lsr lsr lsr lsr sta zp by: lda zp rol rol rol and #$07 ; if you need the ZEROs sta zp Any comments are welcome. daniel ---------------------------------------------------------------------- To unsubscribe from the list send mail to majordomo_at_musoftware.de with the string "unsubscribe cc65" in the body(!) of the mail.
This archive was generated by hypermail 2.1.3 : 2001-12-14 22:05:40 CET