[astrange]

__builtin_expect is good for error handling code, because gcc can avoid size-increasing optimizations in that path, and it can even move all the unlikely code out into another section so it won't take up space in your caches.

But its code generation is better for a 99%/1% case than a 60%/40% case, because Intel doesn't listen to branch hints anymore nor really give advice on how to tune for them.