Re: [Qemu-devel] [PATCH v4 2/2] target-m68k: add 680x0 divu/divs variants

[Laurent Vivier]

Hi,

I come back on some patches as I've been able to test some instructions
using RISU.

Le 01/11/2016 à 21:03, Laurent Vivier a écrit :
...
> --- a/target-m68k/op_helper.c
> +++ b/target-m68k/op_helper.c
> @@ -179,51 +184,178 @@ void HELPER(raise_exception)(CPUM68KState *env, 
> uint32_t tt)
>      raise_exception(env, tt);
>  }
>  
> -void HELPER(divu)(CPUM68KState *env, uint32_t word)
> +void HELPER(divuw)(CPUM68KState *env, int destr, uint32_t den)
>  {
> -    uint32_t num;
> -    uint32_t den;
> -    uint32_t quot;
> -    uint32_t rem;
> +    uint32_t num = env->dregs[destr];
> +    uint32_t quot, rem;
>  
> -    num = env->div1;
> -    den = env->div2;
> -    /* ??? This needs to make sure the throwing location is accurate.  */
>      if (den == 0) {
> -        raise_exception(env, EXCP_DIV0);
> +        raise_exception_ra(env, EXCP_DIV0, GETPC());
>      }
>      quot = num / den;
>      rem = num % den;
>  
> -    env->cc_v = (word && quot > 0xffff ? -1 : 0);
> +    env->cc_c = 0; /* always cleared, even if overflow */
> +    if (quot > 0xffff) {
> +        env->cc_v = -1;
> +        /* nothing else is modified */
> +        /* real 68040 keeps Z and N on overflow,
> +         * whereas documentation says "undefined"
> +         */
> +        return;
> +    }
> +    env->dregs[destr] = deposit32(quot, 16, 16, rem);
>      env->cc_z = quot;
>      env->cc_n = quot;

quot is here a 32bit, but the result is only the 16 lower bits, so I
think we should have

    env->cc_z = (int16_t)quot;
    env->cc_n = (int16_t)quot;

> +    env->cc_v = 0;
> +}
> +
> +void HELPER(divsw)(CPUM68KState *env, int destr, int32_t den)
> +{
> +    int32_t num = env->dregs[destr];
> +    uint32_t quot, rem;
> +
> +    if (den == 0) {
> +        raise_exception_ra(env, EXCP_DIV0, GETPC());
> +    }
> +    quot = num / den;
> +    rem = num % den;
> +
> +    env->cc_c = 0; /* always cleared, even if overflow */
> +    if (quot != (int16_t)quot) {
> +        env->cc_v = -1;
> +        /* nothing else is modified */
> +        /* real 68040 keeps Z and N on overflow,
> +         * whereas documentation says "undefined"
> +         */
> +        return;
> +    }
> +    env->dregs[destr] = deposit32(quot, 16, 16, rem);
> +    env->cc_z = quot;
> +    env->cc_n = quot;

Same here:

    env->cc_z = (int16_t)quot;
    env->cc_n = (int16_t)quot;

Thanks,
Laurent