FWIW, I recently pushed a commit to master that made loading of Elixir's test suite 33% faster (from 15s to 10s): https://github.com/elixir-lang/elixir/commit/2eb03e4a314c0e6...

Unfortunately, it is a bit too large (and too late) for v1.12, but if loading times have been problematic for you, it would be awesome if you could try master out and let us know in the issues tracker (or in the commit) if you see any improvements.