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

[Laurent Vivier]

Le 01/11/2016 à 21:03, Laurent Vivier a écrit :
> diff --git a/target-m68k/op_helper.c b/target-m68k/op_helper.c
> index 48e02e4..a4bfa4e 100644

> +void HELPER(divull)(CPUM68KState *env, int numr, int regr, uint32_t den)
> +{
> +    uint64_t num = deposit64(env->dregs[numr], 32, 32, env->dregs[regr]);
> +    uint64_t quot;
> +    uint32_t 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 > 0xffffffffULL) {
> +        env->cc_v = -1;
> +        /* nothing else is modified */
> +        /* real 68040 keeps Z and N on overflow,
> +         * whereas documentation says "undefined"
> +         */
> +        return;
> +    }
...
> +
> +void HELPER(divsll)(CPUM68KState *env, int numr, int regr, int32_t den)
> +{
> +    int64_t num = deposit64(env->dregs[numr], 32, 32, env->dregs[regr]);
> +    int64_t quot;
>      int32_t rem;
>  
> -    num = env->div1;
> -    den = env->div2;
>      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 != (int16_t)quot ? -1 : 0);
> +    env->cc_c = 0; /* always cleared, even if overflow */
> +    if (quot != (int32_t)quot) {
> +        env->cc_v = -1;
> +        /* nothing else is modified */
> +        /* real 68040 keeps Z and N on overflow,
> +         * whereas documentation says "undefined"
> +         */
> +        return;
> +    }


On a real 68040, for divsll and divull, Z is unset.
(while divsw/divuw don't modify it as we do).

So I will update the patch with this behavior.

Laurent