//   R3 = a
//   R4 = alen
//   R5 = b
//   R6 = blen
//   R7 = address of output word (stores -1/0/1 here)
TEXT cmpbody<>(SB),NOSPLIT|NOFRAME,$0-0
	CMPBEQ	R3, R5, cmplengths
	MOVD	R4, R8
	CMPBLE	R4, R6, amin
	MOVD	R6, R8
amin:
	CMPBEQ	R8, $0, cmplengths
	CMP	R8, $256
	BLE	tail
loop:
	CLC	$256, 0(R3), 0(R5)
	BGT	gt
	BLT	lt
	SUB	$256, R8
	MOVD	$256(R3), R3
	MOVD	$256(R5), R5
	CMP	R8, $256
	BGT	loop
tail: