Evaluate Profile-Guided Optimization (PGO) and LLVM BOLT

[zamazan4ik]

Hi!

Recently I checked Profile-Guided Optimization (PGO) improvements on multiple projects. The results are here.

Since PGO showed measurable improvements in compiler-like workloads (Clang, GCC, Rustc, etc.) I think it could be helpful to check PGO for the Redex project too.

We need to perform PGO benchmarks on Redex. And if it shows improvements - add a note to the documentation about possible improvements in Redex performance with PGO. Providing an easier way (e.g. a build option) to build scripts with PGO can be useful for the maintainers and end-users too. Reducing optimization time is important for CI and local developers' experience.

Also, since Facebook created BOLT (LLVM BOLT) I think would be great to see BOLT results on Redex as well.