On 2/5/19 4:22 PM, David Hildenbrand wrote:
> +static inline bool float128_is_normal(float128 a)
> +{
> + return ((a.high + (1ULL << 47)) & -1ULL >> 1) >= 1ULL << 48;
I believe this is off by one: 1 << 48 and >= 1 << 49.
The exponent is at [62:48]. The trick is adding 1, letting Inf+NaN overflow
into the sign, masking out the sign, and checking that the result >= 2 to
eliminate Inf+NaN (0) and Zero+Denormal (1).
I think this is clearer as
(((a.high >> 48) + 1) & 0x7fff) >= 2.
It might be worth applying this to the other formats for clarity...
r~
