GCC 4.0 vs. 3.5

[Robert Dewar]

I am pretty sure that tree-ssa will have a major impact on some users (i.e.
their code will behave differently, e.g. because they have made some
improper assumptions that the optimizer now handles differentlyh). We
reallydon't have much input yet on how large critical programs manage
with the new technology (large here to me = millions of lines).

I would not be at all surprised if we (AdaCore hat on now) have to maintain
the two technoloogies in parallel for a while. Given pretty major changes
in the front end (to go to function at a time), there may well be new
instabilities. This kind ofparallel maintenance is simpler if we
have clearly designated differences. Of course GNAT Pro version numbers
are separate anyway, so we can go to a new major version indepedently,
but it would be clearer if the GCC technology also changes major
version numbers.

Robert