A 44% percent penalty sounds perfectly reasonable as a temporary situation until the compiler improves, given that the API is simpler and more consistent by using nothing everywhere to represent the absence of a match.
The nothing_sentinel trick is only used 7 times, all in the same file. It’s also not strictly needed and is mostly due to the fact that the old code was designed around the assumption that 0 indicated no match. Since we’re short on time we kept it that way in order to get it merged quickly (see discussion on the PR.