FWIW, this is basically an implementation of perfect hashing, and there's a myriad of different strategies. Sometimes “switch on length + well-chosen characters” are good, sometimes you can do better (e.g. just looking up in a table instead of a long if chain).

The “value speculation” thing looks completely weird to me, especially with the “volatile” that doesn't do anything at all (volatile is generally a pointer qualifier in C++). If it works, I'm not really convinced it works for the reason the author thinks it works (especially since it refers to an article talking about a CPU from the relative stone age).