Why are compilers so stupid?

Question

I always wonder why compilers can\'t figure out simple things that are obvious to the human eye. They do lots of simple optimizations, but never something even a little bit

Answer 1

Premise: I studied compilers at university.

The javac compiler is extremely stupid and performs absolutely no optimization because it relies on the java runtime to do them. The runtime will catch that thing and optimize it, but it will catch it only after the function is executed a few thousand times.

If you use a better compiler (like gcc) enabling optimizations, it will optimize your code, because it's quite an obvious optimization to do.