rmu4.s

操作系统源代码

.define .rmu4
.text

yl=6
yh=8
xl=10
xh=12

.rmu4:
	push	si
	push	di
	mov     si,sp           ! copy of sp
	mov     bx,yl(si)
	mov     ax,yh(si)
	or      ax,ax
	jne     7f
1:
	xor     dx,dx
	mov     cx,xl(si)
	mov     ax,xh(si)
2:
	div     bx
	xchg    ax,cx
	div     bx
	xor     bx,bx
9:
			! bx is high order result
			! dx is low order result
	mov	ax,dx
	mov	dx,bx
	pop	di
	pop	si
	ret	8	! result in ax/dx

7:
	mov     di,ax
	xor     bx,bx
	mov     ax,xl(si)
	mov     dx,xh(si)
	mov     cx,#16
1:
	shl     ax,#1
	rcl     dx,#1
	rcl     bx,#1
	cmp     di,bx
	ja      3f
	jb      2f
	cmp     yl(si),dx
	jbe     2f
3:
	loop    1b
		! dx=result(low), bx=result(high)
	jmp     9b
2:
	sub     dx,yl(si)
	sbb     bx,di
	inc     ax
	loop    1b
1:
		! dx=result(low), bx=result(high)
	jmp     9b