mpy16s.s

avr的icc编译器的源代码

;	fast 16x16=16 multiply

	.text
mpy16s::
	st -Y,r0
	st -Y,r1
	clr r0
	clr r1
loop:
	cpi r16,0
	cpc r16,r17
	breq done
	lsr r17
	ror r16
	brsh skip
	add r0,r18
	adc r1,r19
skip:
	lsl r18
	rol r19
	rjmp loop
done:
	mov r16,r0
	mov r17,r1
	ld r1,Y+
	ld r0,Y+
	ret