Note that unicode_eq() always called after identity check and hash check. I.e. identity check in Victor's patch is redundant and unicode_eq() called only for strings which have the same hash. The probability to have the same first byte and be equal is a great.

unicode_compare_eq() and unicode_eq() are designed for different purposes. They cannot be just merged.

As the optimization for unicode_eq(), I would have suggested a checking of first machine words instead of first bytes, but this trick is too dirty.