fe_isnegative
s[31] ^= fe_isnegative(&x) << 7;
if (fe_isnegative(&h->X) != (s[31] >> 7)) {
s[31] ^= fe_isnegative(x) << 7;
s[31] ^= fe_isnegative(x) << 7;
if (fe_isnegative(h->X) != (s[31] >> 7)) {