I recently refactored some signal processing code at work. My goal was to both make the code more maintainable as well as reverse engineer what it was doing. Most of the code was contained in a few large functions that could not be understood readily. I broke it up into many smaller functions that did one thing, keeping the code otherwise the same, and not only is it now easier to understand, but the compiler produced faster code. About 15 to 30 % reduction in runtime. (I verified the new code has exactly the same signal response as the old code.)