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;
; Ullrich von Bassewitz, 05.08.1998
; Christian Krueger, 11-Mar-2017, ímproved 65SC02 optimization
; CC65 runtime: long sub
;
;
; EAX = TOS - EAX
;
.export tossub0ax, tossubeax
.import addysp1
.importzp sp, sreg
.macpack cpu
tossub0ax:
.if (.cpu .bitand ::CPU_ISET_65SC02)
stz sreg
stz sreg+1
.else
ldy #$00
sty sreg
sty sreg+1
.endif
tossubeax:
sec
eor #$FF
.if (.cpu .bitand ::CPU_ISET_65SC02)
adc (sp) ; 65SC02 version - saves 2 cycles
ldy #1
.else
ldy #0
adc (sp),y ; lo byte
iny
.endif
pha ; Save low byte
txa
eor #$FF
adc (sp),y ; byte 1
tax
iny
lda (sp),y
sbc sreg ; byte 2
sta sreg
iny
lda (sp),y
sbc sreg+1 ; byte 3
sta sreg+1
pla ; Restore byte 0
jmp addysp1 ; Drop TOS
|
