/**
 * @r0=@r0-@r1
 * r7=len
 */
void long_xsub() __naked
{
	__asm
	.globl long_xsub
	.globl long_xsubb
long_xsub:
	clr	c
long_xsubb:
	movx	a,@r1
	mov	b,a
	movx	a,@r0
	subb	a,b
	movx	@r0,a
	inc	r0
	inc	r1
	djnz	r7,long_xsubb
	ret

	__endasm;
}