cc65/libsrc/runtime/lshelp.s

;
; Ullrich von Bassewitz, 13.08.1998
;
; CC65 runtime: helper stuff for mod/div/mul with long signed ints
;

; When negating values, we will ignore the possibility here, that one of the
; values if $80000000, in which case the negate will fail.

       	.export		poplsargs
	.import		getlop
	.importzp	sreg, tmp1, tmp2, ptr1, ptr3, ptr4

poplsargs:
	jsr	getlop	   	; Get the operands

; Remember the signs of the operands (that is, the high bytes) in tmp1 and
; tmp2. Make both operands positive.

	lda   	sreg+1		; Is the left operand negative?
        sta     tmp1            ; Remember the sign for later
	bpl   	L1		; Jump if not

	clc			; Make it positive
	lda	ptr1
	eor	#$FF
	adc	#$01
	sta	ptr1
	lda	ptr1+1
	eor	#$FF
	adc	#$00
	sta	ptr1+1
	lda	sreg
	eor	#$FF
	adc	#$00
	sta	sreg
	lda	sreg+1
	eor	#$FF
	adc	#$00
	sta	sreg+1

L1:	lda	ptr4+1		; Is the right operand nagative?
        sta     tmp2            ; Remember the sign for later
	bpl	L2		; Jump if not

	clc			; Make it positive
	lda	ptr3
	eor	#$FF
	adc	#$01
	sta	ptr3
	lda	ptr3+1
	eor	#$FF
	adc    	#$00
	sta	ptr3+1
	lda	ptr4
	eor	#$FF
	adc	#$00
	sta	ptr4
	lda	ptr4+1
	eor	#$FF
	adc	#$00
	sta	ptr4+1

L2:	rts