I posted a reply, but I think ultimately this is just a coincidence. There's a naïve reason that "mov S P" looks redundant ("just use S instead of P later"), but in typical GPT fashion, this is specious, and can't actually be done. It's essentially trying to swap two variables without using a temporary. If x86 had a conditional swap instruction, it could, but it doesn't, and just doing "cmp,cmov,cmov" can't handle it.<p>Another giveaway is that removing that line in the real optimization changes the output of the provided snippet if C < B. It feels like a hard sell to say GPT picked this line for that subtle reason based on information not provided, but explained it with something only correct at surface level.