.text
.global _gcd
_gcd:
	mov r0,#9
	mov r1,#15
	b loop
loop:
	cmp r0,r1
	beq stop
	subhi r0,r1
	bhi loop
	subcc r1,r0
	bcc loop

stop:
	b stop
	.end
		

用for循环实现1~100之间和5050

.text
.global _gcd
_gcd:
	mov r0,#0x0
	mov r1,#0x1
	mov r2,#0x64
	b loop
loop:
	cmp r1,r2
	bhi stop
	add r0,r0,r1
	add r1,#0x1
	b loop

stop:
	b stop
	.end