keyg_sign
signed_vals.keyg = (hwcaps & HWCAP_PACG) ? keyg_sign(val) : 0;
size_t keyg_sign(size_t val);
keyg |= keyg_sign(i) & PAC_MASK;
before = keyg_sign(ARBITRARY_VALUE);
after = keyg_sign(ARBITRARY_VALUE);
sign->keyg = keyg_sign(val);