SI_HASH
for (sp = si_cachei[SI_HASH(ip->i_shadow)]; sp; sp = sp->s_forw)
for (sp = si_cachea[SI_HASH(spi->s_signature)]; sp; sp = sp->s_next) {
tspp = &si_cachea[SI_HASH(sp->s_signature)];
tspp = &si_cachei[SI_HASH(sp->s_shadow)];
hash = SI_HASH(signature);
hash = SI_HASH(sp->s_shadow);