BN_NIST_521_LSHIFT
#define BN_NIST_521_TOP_MASK ((BN_ULONG)BN_MASK2 >> BN_NIST_521_LSHIFT)
t_d[i] = (tmp | val << BN_NIST_521_LSHIFT) & BN_MASK2;
t_d[i] = (val >> BN_NIST_521_RSHIFT | (tmp = t_d[i + 1]) << BN_NIST_521_LSHIFT) & BN_MASK2;