ILL_BTCFI
if (si->si_signo == SIGILL && si->si_code == ILL_BTCFI)
code = (frame->tf_err & 0x7fff) < 4 ? ILL_BTCFI
trapsignal(p, SIGILL, esr, ILL_BTCFI, sv);
if (code == ILL_BTCFI) {