Function matched 

unsafe fn matched(start: *const u8, cur: *const u8, chunki: usize) -> usize

Accepts a chunk-relative offset and returns a haystack relative offset.

This used to be marked #[cold] and #[inline(never)], but I couldn’t observe a consistent measureable difference between that and just inlining it. So we go with inlining it.

Safety

Same at ptr::offset_from in addition to cur >= start.