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C64 soft80-conio cgetc: save 14 cycles in invertcursor

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By 'inverting' the loop, we can save 16 cycles by removing the `cpy #8`,
saving 16 cycles. But we need an extra `ldy #7` at the start of the
loop, so the total cycles saved is 14. Code size doesn't increase due to
the addition of the `ldy #7` negating the removal of the `cpy #xx`.
This commit is contained in:
compyx
2020-07-11 13:18:14 +02:00
committed by Oliver Schmidt
parent 2c4dd5decf
commit 381a32d9aa
1 changed files with 4 additions and 5 deletions
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9
libsrc/c64/soft80_cgetc.s
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@@ -46,17 +46,16 @@ invertcursor:
lda #$34 lda #$34
sta $01 sta $01
ldy #$00
jsr setcolor jsr setcolor
ldx soft80_internal_cursorxlsb ldx soft80_internal_cursorxlsb
ldy #7
@lp1: @lp1:
lda (SCREEN_PTR),y lda (SCREEN_PTR),y
eor nibble,x eor nibble,x
sta (SCREEN_PTR),y sta (SCREEN_PTR),y
iny dey
cpy #8 bpl @lp1
bne @lp1
pla pla
sta $01 ; enable I/O sta $01 ; enable I/O
@@ -67,7 +66,7 @@ invertcursor:
; shown using the current textcolor without disturbing the "color voodoo" ; shown using the current textcolor without disturbing the "color voodoo"
; in soft80_cputc ; in soft80_cputc
setcolor: setcolor:
;ldy #0 ; is 0 ldy #0
bcs @set bcs @set
; restore old value ; restore old value
lda tmp1 lda tmp1