> you should normally optimise for speed, not binary size IME optimize for speed vs size usually isn't as clear cut as the name says though, sometimes smaller

> you should normally optimise for speed, not binary size IME optimize for speed vs size usually isn't as clear cut as the name says though, sometimes smaller code does indeed run faster, but in most cases I've seen there's not much of a difference between -O3, -O2, -Os and -Oz.