1.

.text
.globl _start

_start:
	mov r0,#0x9
	mov r1,#0xf
	bl loop
loop:
	cmp r0,r1
	beq stop
	subhi r0,r1
	subls r1,r0
	mov pc,lr
stop:
	b stop

 2.实现1-100的和

.text
.globl _start

_start:
	mov r0,#0x1
	bl loop
loop:
	cmp r0,#0x64
	bhi stop
	addls r1,r0
	addls r0,#0x1
	mov pc,lr
stop:
	b stop