mirror of
https://github.com/cc65/cc65.git
synced 2024-11-18 15:05:14 +00:00
64 lines
1.6 KiB
ArmAsm
64 lines
1.6 KiB
ArmAsm
;
|
|
; Ullrich von Bassewitz, 07.04.2000
|
|
; Christian Krueger, 12-Mar-2017, added 65SC02 optimization
|
|
;
|
|
; CC65 runtime: -= operator
|
|
;
|
|
; On entry, the low byte of the address of the variable to decrement is
|
|
; in ptr1, the high byte is in Y, and the decrement is in eax.
|
|
;
|
|
|
|
.export lsubeq1, lsubeqa, lsubeq
|
|
.importzp sreg, ptr1
|
|
|
|
.macpack cpu
|
|
|
|
lsubeq1:
|
|
lda #$01
|
|
|
|
lsubeqa:
|
|
ldx #$00
|
|
stx sreg
|
|
stx sreg+1
|
|
|
|
lsubeq: sty ptr1+1 ; Store high byte of address
|
|
|
|
sec
|
|
eor #$FF
|
|
.if (.cpu .bitand ::CPU_ISET_65SC02)
|
|
adc (ptr1) ; Subtract byte 0
|
|
sta (ptr1)
|
|
ldy #$01 ; Address byte 1
|
|
.else
|
|
ldy #$00 ; Address low byte
|
|
adc (ptr1),y ; Subtract byte 0
|
|
sta (ptr1),y
|
|
iny ; Address byte 1
|
|
.endif
|
|
pha ; Save byte 0 of result for later
|
|
txa
|
|
eor #$FF
|
|
adc (ptr1),y ; Subtract byte 1
|
|
sta (ptr1),y
|
|
tax
|
|
|
|
iny ; Address byte 2
|
|
lda (ptr1),y
|
|
sbc sreg
|
|
sta (ptr1),y
|
|
sta sreg
|
|
|
|
iny ; Address byte 3
|
|
lda (ptr1),y
|
|
sbc sreg+1
|
|
sta (ptr1),y
|
|
sta sreg+1
|
|
|
|
pla ; Retrieve byte 0 of result
|
|
|
|
rts ; Done
|
|
|
|
|
|
|
|
|