will Perl5-on-LLVM be considered not related to Perl development?
First off, any discussions about the future directions(s) of perl5 is on-topic. Secondly, if the plan is for any LLVM enhancements to be included in the current perl core, then its definitely on-topic. If the the plan is to produce a completely separate product (e.g. the perlito approach), then after some initial discussion, you might want to take the day-to-day development discussions onto a new list.
Of course, I'm not promising that p5p will be interested in, or warm to, such topics.