LLVM 9 versus LLVM 8

[Joe A.]

Greetings....

My current machine's state:

FreeBSD 12.0-RELEASE-p11 r354060 CHTHONIXIA  amd64

Recently, LLVM was updated to version 9. I do not recall why; but I think 
some port required version 9. Since 9 appeared to become the default 
version I deinstalled 8, assuming LLVM 9 was preferred.

But now I'm not sure if LLVM 9 was set to the default version for 
Freebsd, or even if it is needed. 

Now I need to update firefox, which attempts to install LLVM 8. 

Can I dispense with LLVM 9 by a deinstall, and depend on LLVM 8 for a 
functioning, X-enabled, desktop? Or must I have both LLVM 8 and 9 as 
things stand now for 12.1?

Thanks, 

Joe