Definitely, but I think it's unlikely that it will close the gap much between the fast and slow std::toupper() compilations (my own toupper is mostly just in th

Definitely, but I think it's unlikely that it will close the gap much between the fast and slow std::toupper() compilations (my own toupper is mostly just in there as an interesting reference point). In addition to more instructions and a function call, the slow version has many more memory dereferences, so if everything is very cold it is likely to suffer more misses.