MPN_SQR_N_RECURSE
MPN_SQR_N_RECURSE (prodp, up, esize, tspace);
MPN_SQR_N_RECURSE (prodp + size, up + hsize, hsize, tspace);
MPN_SQR_N_RECURSE (tspace, prodp, hsize, tspace + size);
MPN_SQR_N_RECURSE (tspace, up, hsize, tspace + size);