based on what "fishgoesblub" commented, building - read: `emerge -e @world` - a gentoo system with profiling forced, and then using it in that "degraded" state for a while ought to be able to inform PGO, right? if there's a really good speedup from putting hot code together, the hottest code after moderate use should suffice to speed up things, and this could continually be improved.

I'm also certain that if there were a way to anonymously share profiling data upstream (or to the maintainers), that would decrease the "degradation" from the first step, above. I am 100% spitballing here. I'm a dedicated gentoo sysadmin, but i know only a small bit about optimization of the sort being discussed here. So it is possible that every user would have to do the "unprofiled profiler" build first, which, if one cares, is probably a net negative to the planet, unless the idea pans out, then it's a huge positive for the planet - man hours, electricity, wear/endurance on parts, etc.

It would be difficult as every package/program would need a step to generate the profile data by executing and running the program like the user would.