@ela how can the compiler break down a recursive function to a mathematical statement? There is no brute force involved or is there? And does it do that only when optimizations are on?

@viduq It's not exactly brute force, but it does involve some heavy lifting in the optimizer. Tail recursion elimination turns the recursive calls into a loop. Then, induction variables of the loop are detected, and finally strength reduction, algebraic simplification finish it off.