In my opinion "//do something" takes longer than those comparisons, so it's not worth wasting time on optimizing for() when you can use it to optimize its contents. Also bear in mind that despite you write some statement in your code, the compiler makes optimizations so the final binary code might look different. After all it all goes down to using BNE or similar so as long as its argument is constant (needs not to be recalculated with each iteration) there is no difference in execution time.