But he didn't set the compiler option, he rewrote it to explicitly use those instructions, that is micro optimization no matter how you look at it. The reason m

But he didn't set the compiler option, he rewrote it to explicitly use those instructions, that is micro optimization no matter how you look at it. The reason micro optimization is so easy to get better than compiler results is that you know things about the data the compiler doesn't, like in this case you know it is fine to reorder the result while the compiler is too dumb to know that. You need much smarter compilers than we have today in order for such micro optimizations to stop paying dividends.