Problem with ssa optimization making an uninitialized variable

[Richard Kenner]

    If you get this, it means that we have been able to remove
    TREE_ADDRESSABLE from v4 and now we consider v4 a local variable. 
    Either compute_may_aliases got it wrong or the FE is not telling the
    optimizers something about v4.  Or maybe v4 really is uninitialized in
    the source code?

OK, thanks.

That pinned it down.

The problem was that I wasn't emitting the gotos out of each case in a
switch statement, so all the cases fell through and the statements that
took the address ended up being deleted.

At this point I can compile the entire Ada RTS without any ICEs or
unexpected warnings.