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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
sta $01
ldy #$00
jsr setcolor
ldx soft80_internal_cursorxlsb
ldy #7
@lp1:
lda (SCREEN_PTR),y
eor nibble,x
sta (SCREEN_PTR),y
iny
cpy #8
bne @lp1
dey
bpl @lp1
pla
sta $01 ; enable I/O
@ -67,7 +66,7 @@ invertcursor:
; shown using the current textcolor without disturbing the "color voodoo"
; in soft80_cputc
setcolor:
;ldy #0 ; is 0
ldy #0
bcs @set
; restore old value
lda tmp1