> matrix multiply probably one of the easy cases? I suppose the compiler must be able to somehow prove to itself that the code does not do anything else. What

> matrix multiply probably one of the easy cases? I suppose the compiler must be able to somehow prove to itself that the code does not do anything else. What if, for example, within the loop you "printf(column)" or something like that? In this case re-arranging the loop would produce a different result, wouldn't it? So the compiler probably will not optimize it in that case, would it?