I think the tricks are more like "use dynamic dispatch instead of static dispatch". O1 vs O3 is probably a fair way to do things. Some people will do that for

I think the tricks are more like "use dynamic dispatch instead of static dispatch". O1 vs O3 is probably a fair way to do things. Some people will do that for debug builds, to get a mix of reasonable performance (for tests) and reasonable compile times. I'm not sure how meaningful the difference is going to be between O2 and O3, it's been a long time since I'd looked into it, and back then O3 wasn't really a thing people did.