Re: [Qemu-devel] [PATCH 4/4] target-m68k: add fscale, fgetman and fgetexp

[Richard Henderson]

On 07/03/2017 09:23 AM, Laurent Vivier wrote:
> +void HELPER(fgetman)(CPUM68KState *env, FPReg *res, FPReg *val)
> +{
> +    if (floatx80_is_infinity(val->d)) {
> +        res->d = floatx80_default_nan(NULL);
> +        /* FIXME: set the OPERR bit int he FPSR */
> +        return;
> +    }
> +    if (floatx80_is_zero(val->d) ||
> +        floatx80_is_any_nan(val->d)) {
> +        *res = *val;
> +        return;
> +    }
> +
> +    res->l.upper = (val->l.upper & 0x8000) | 0x3fff;
> +    if (floatx80_is_zero_or_denormal(val->d)) {
> +        res->l.lower = val->l.lower << 1;

Surely you have to do more than this for denormals?  There may be more than one 
leading zero bit in the mant.  Do you actually need to re-normalize?  Or does 
real hardware produce a so-called "unnormal" in this situation?


r~