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cc65/libsrc/runtime/icmp.s

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;
; Ullrich von Bassewitz, 10.12.1998
;
; Integer compare function - used by the compare operators
;
.export tosicmp
.import incsp2
.importzp sp, sreg
tosicmp:
sta sreg
stx sreg+1 ; Save ax
ldy #$01
lda (sp),y ; Get high byte
tax
dey
lda (sp),y ; Get low byte
; Inline incsp2 for better performance
inc sp ; 5
bne @L1 ; 3
inc sp+1 ; (5)
@L1: inc sp ; 5
bne @L2 ; 3
inc sp+1 ; (5)
; Do the compare.
@L2: cpx sreg+1 ; Compare high byte
bne @L3
cmp sreg ; Compare low byte
beq @L3
bcs @L4
lda #$FF ; Set the N flag
@L3: rts
@L4: lda #$01 ; Clear the N flag
rts