MC68000: Divide by 3

Question

I'm using shift operations to divide a long word in register D3 by three and storing the result in memory address specified by A2:

Move.L  D1, D2, D3, -(SP)
        CLR.L   D5
        MOVE.B  #1, D4

Loop    LSR.L   D2, D3
        ROXR.L  #1,D5
        BCS     DONE
        SUBI.B  #1, D2
        BLT     Loop
        CLR.B   D4

DONE    MOVE.L  (SP)+, D3, D2, D1
        RTS

        END

Is this correct?

Answer 1

Let's ask a couple of questions first:

1. What is your assignment, really?
2. If it's to implement division by hand, then you're taking a funny approach. If it's simply to divide by 3, why not use the divs (divide signed) instruction and be done with it?
3. How come you don't do anything with the result?
4. You're going to the trouble of saving and restoring registers d1-d3, but you're torching d4 and d5 - why is that?
5. Do you understand the 68K's indirect addressing?
6. Is the result expected to be a word or a long word?