Reorder some tree codes

[Richard Kenner]

    I'm sympathetic to the idea that it would be cooler to improve the
    middle end so that it did this optimization itself, but I don't know
    how hard that would be.  Does anyone have an idea about that?  (The
    documentation issue remains in this case, in that someone might
    reorder the codes, and then we have a performance degradation, if it's
    no longer possible to collapse the checks into a range check.)

I think it will now *if* the codes are all tested in order.