tanPi is available in latest MPFR, so rather trivial to add, if wanted for only BigFloat:
https://github.com/JuliaLang/julia/pull/48165#issuecomment-1374927783
See there about possible solution for e.g. Float64.
This issue can be closed. At least the tanpi
part. I did not (and don't plan to) implement "more required from latest IEEE".
I see #32877, which talks about the other IEEE functions. So you should close this issue.