If they're rare enough that they are ~never mispredicted then why does the cost of exceptions matter when they do happen? If they are common, then they're going

If they're rare enough that they are ~never mispredicted then why does the cost of exceptions matter when they do happen? If they are common, then they're going to be mispredicted. The demo benchmark, for example, would produce basically always missed branches. Well, if would if the compiler didn't just strip the empty branch, invalidating the entire benchmark.