FWIW: This is actually not that great, but it's a good start.

You should be able to get about 15-20% with about 3-5% binary increase size.

In fact, with ThinLTO, we often see that gain with binary size decrease from smart inlining choices.

(The heuristics for inlining take a very very long time to get right and tune)

The issue they will next hit is that inlining is going to make the compiler slower until they tune the heuristics well.