Figuring out which compiler optimizations did fire, and which still need to be done by hand, is also extremely difficult. Compilers generally don't tell you. S

Figuring out which compiler optimizations did fire, and which still need to be done by hand, is also extremely difficult. Compilers generally don't tell you. So while in principle one should be able to expect a compiler to do the $1/x$ optimization all by itself, it might be important enough to just do it by hand and get on with things.