strncmp.s

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

TEXT	strncmp(SB), $0
#define	BDNZ	BC	16,0,

	MOVW	s2+4(FP), R4
	MOVW	n+8(FP), R7

	CMP	R7, $0
	MOVW	R7, CTR
	BLE	eq

	SUB	$1, R3
	SUB	$1, R4
l1:
	MOVBZU	1(R3), R5
	MOVBZU	1(R4), R6
	CMP	R5, R6
	BNE	ne
	CMP	R5, $0
	BEQ	eq
	BDNZ	l1
eq:
	MOVW	$0, R3
	RETURN
ne:
	MOVW	$1, R3
	BGT	ret
	MOVW	$-1, R3
ret:
	RETURN