Since the compiler took advantage of it, doesn't it mean that the speedup is a well-known effect in the circumstances the compiler encountered? I'm nitpicking s

Since the compiler took advantage of it, doesn't it mean that the speedup is a well-known effect in the circumstances the compiler encountered? I'm nitpicking slightly on "paradoxical" and "chaotic". The behavior may be documented but to a human that does not remember every little rule, it may seem random.