From: groepaz (groepaz_at_gmx.net)
Date: 2001-06-25 14:11:03
Hello daniel, Monday, June 25, 2001, 1:54:02 PM, you wrote: dp> 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) dp> Aha! you are saving THREE-cycles. dp> We are so little on registers that we always, me at least, need dp> every-REgister busy. therefor saving/restoring the INDEX-Reg. 3+3 dp> cycles. So we are THREE-cycles MINUS! dp> as far as I had experienced the SHIFT-things is the LAST thing to dp> optimize. If you have more than FOUR shifts, like in your example, you dp> shift the the other way round: dp> replace: dp> lda zp dp> lsr dp> lsr dp> lsr dp> lsr dp> lsr dp> sta zp dp> by: dp> lda zp dp> rol dp> rol dp> rol dp> and #$07 ; if you need the ZEROs dp> sta zp dp> Any comments are welcome. well all i can say to that is, that ofcoz the above optimization dont make any sence if the index-register isnt available anyway -- Best regards, groepaz mailto:groepaz_at_gmx.net ---------------------------------------------------------------------- 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