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use faster memset algoritm.

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hugova 2025-07-26 14:50:23 +02:00
parent 7f136b9ed2
commit ef22e5a2ff
2 changed files with 80 additions and 41 deletions
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118
wip-hugo/routines/memory/memset.s Executable file → Normal file
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@ -1,40 +1,78 @@
;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
;; Sets memory in 'A'-registry to all addresses from 'A_start' until 'A_start' + 'length'
;; Modifies A, X and A_start
.proc memset
.include "mem.inc"
;; big_set sets the memory in $ff chunks.
;; skipp if length >= $ff
LDX length +1
BNE big_set
JMP small_set
big_set: ;sets $ff of memory
;; Y value do not matter, will go through all anyway!
.repeat $ff
STA (A_start), Y
DEY
.endrepeat
STA (A_start), Y ; dont forget Y =0
big_set_end:
;;set all hole $ff memory chunks!
INC A_start + 1
DEX ;; length +1 --
BEQ small_set
JMP big_set
;;sets the rest of the memory
;; note that this can use code above (smc) or the same method. may implement later.
small_set:
LDY length
small_set_loop:
STA (A_start), Y
DEY
BNE small_set_loop
STA (A_start), Y
RTS
.endproc
;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
;; Sets memory in 'A'-registry to all addresses from 'A_start' until 'A_start' + 'length'
;; Modifies A, X and A_start
.proc memset
.include "mem.inc"
;; big_set sets the memory in $ff chunks.
;; skipp if length >= $ff
LDX length +1
BNE big_set
JMP small_set
big_set: ;sets $ff of memory
;; Y value do not matter, will go through all anyway!
.repeat $ff
STA (A_start), Y
DEY
.endrepeat
STA (A_start), Y ; dont forget Y =0
big_set_end:
;;set all hole $ff memory chunks!
INC A_start + 1
DEX ;; length +1 --
BEQ small_set
JMP big_set
;; Note that cpu cykels total: cy_tot = 66 to 69
;; But we skipp a BNE (cy = 2*) * [length (mod 255)]
;; The BNE case has an avrige of 2*255/2 = 255 so this is faster (on avrige.)
small_set:
STA data_to_write ; cy = 3
LDA length ; cy = 3
STA length_copy ; cy = 3
;; calculate rts-position
LDX #$00 ; cy = 2
STX length + 1 ; cy = 3
;; 3 bytes = STA DEY NOP = seting 1 byte of memory.
;; So we need to calculate: length*3
Mult_16 A, length + 1 ; cy = 7
; A= length
ADC length_copy ; cy = 3
TAY
LDA length + 1 ; cy = 3
ADC #$00 ; cy = 2
STA length + 1 ; cy = 3
;; Now RTS_pointer + Y = length*3 + big_set_label
LDA #<big_set ; cy = 2
STA RTS_pointer ; cy = 3
LDA #>big_set ; cy = 2
ADC length + 1 ; cy = 3
STA RTS_pointer + 1 ; cy = 3
;; read data we will change to RTS
STY Y_copy ; cy = 3
LDA (RTS_pointer), Y ; cy = 5*
TAX ; cy = 2
;; set RTS in big_set
LDA #$60 ; cy = 2
STA (RTS_pointer), Y ; cy = 5*
;; JSR to modified big_set
LDY length_copy ; cy = 3
DEY ; because we want to count to Y=0 :)
LDA data_to_write ; cy = 3
JSR big_set ; cy = 6
;; revert changes
LDY Y_copy ; cy = 3
TXA ; cy = 2
STA (RTS_pointer), Y ; cy = 5*
RTS
.endproc

3
wip-hugo/source.s
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@ -33,7 +33,8 @@ JMP exit
.include "routines/pixel/pixel_draw.s"
.include "routines/pixel/pixel_calc.s"
.include "routines/text/char_draw.s"
.include "routines/memory/memset_alt.s"
.include "routines/memory/memset.s"
;.include "routines/memory/clear_screen.s"
.include "routines/memory/memcpy.s"
.include "routines/arithmatic/mult.s"
.include "routines/arithmatic/div.s"