68000: Suggestion for additional DIVS/DIVU test cases

[jsgroth]

I believe there are currently no test cases for either DIVS or DIVU where the quotient is zero. If I modify my 68k DIVS and DIVU implementations to hardcode the Z flag to false, it still passes all of the DIVS and DIVU test cases.

I noticed this because I had a silly bug in my implementation where I was setting the Z flag based on the final 32-bit value written back to the register, when as I understand it the correct behavior is to set the Z flag purely based on the 16-bit quotient.

As an example, here is a mostly hand-crafted test case for DIVU that failed in my implementation before the bugfix (minus the bus transactions which I don't currently have a way to generate easily):

{
  "name": "80c1 [DIVU D1, D0] xxxx",
  "initial": {
    "d0": 1,
    "d1": 5,
    "d2": 0,
    "d3": 0,
    "d4": 0,
    "d5": 0,
    "d6": 0,
    "d7": 0,
    "a0": 0,
    "a1": 0,
    "a2": 0,
    "a3": 0,
    "a4": 0,
    "a5": 0,
    "a6": 0,
    "usp": 2763053352,
    "ssp": 2048,
    "sr": 9985,
    "pc": 3072,
    "prefetch": [
      32961,
      40692
    ],
    "ram": [
      [
        3077,
        228
      ],
      [
        3076,
        74
      ]
    ]
  },
  "final": {
    "d0": 65536,
    "d1": 5,
    "d2": 0,
    "d3": 0,
    "d4": 0,
    "d5": 0,
    "d6": 0,
    "d7": 0,
    "a0": 0,
    "a1": 0,
    "a2": 0,
    "a3": 0,
    "a4": 0,
    "a5": 0,
    "a6": 0,
    "usp": 2763053352,
    "ssp": 2048,
    "sr": 9988,
    "pc": 3074,
    "prefetch": [
      40692,
      19098
    ],
    "ram": [
      [
        3077,
        228
      ],
      [
        3076,
        74
      ]
    ]
  },
  "length": 136,
  "transactions": []
}