The cost of `experimental.cttz.elts` in RISC-V equals to the cost of vfirst when the zero_is_poison argument is true. Otherwise, we add additional costs of cmp + select to convert the -1 result from vfirst to EVL.
The cost of `experimental.cttz.elts` in RISC-V equals to the cost of vfirst when the zero_is_poison argument is true. Otherwise, we add additional costs of cmp + select to convert the -1 result from vfirst to EVL.