I'm sorry, but like the other comment at the bottom, your guesses are so far from reality that they are hard to respond to. IACA is great for what it does, but it's a static analyzer and knows nothing about alignment. L0 doesn't even exist on modern Intel processors. Memory fences would change things, but aren't part of the problem as stated. And your guess that "it probably never even gets executed because the instruction should fit in instruction cache and branch prediction cache and all" just doesn't have any bearing on they way processors work.

Your disclaimer does indicate that you have the self-awareness that you are not an expert, but the fact that you are trying to make an argument would normally indicate that you think you understand what's happening to some extent. Rather than just guessing, I think you'd benefit from trying some things out and seeing what the results are. Play with perf, it's fun!