Re: [Qemu-devel] [PATCH v3 15/16] target-m68k: add more FPU instructions

[Richard Henderson]

On 02/07/2017 11:59 AM, Laurent Vivier wrote:
> +static long double floatx80_to_ldouble(floatx80 val)
> +{
> +    if (floatx80_is_infinity(val)) {
> +            if (floatx80_is_neg(val)) {
> +                    return -__builtin_infl();
> +            }
> +            return __builtin_infl();
> +    }
> +    if (floatx80_is_any_nan(val)) {
> +            char low[20];
> +            sprintf(low, "0x%016"PRIx64, val.low);
> +
> +            return nanl(low);
> +    }
> +
> +    return *(long double *)&val;
> +}

This doesn't work except for x86 host.

You ought to extract the mantissa, convert the 64-bit value to long-double, and 
use ldexpl to scale the result for the exponent.

Similarly converting the other way use frexpl and ldexpl.


r~