g++ 3.1 EH broken for irix6.5

[Richard Kenner]

    It is not a question of what the SVR4 ABI specifies -- it a question
    of what we have already done.  If we change this, we have changed
    the meaning of programs written to work with GCC.  

Yes, but that only matters if the programs are using features they are
entitled to use based on documentation.  There are many programs out
there that are erroneous and rely on things GCC doesn't guarantee:
such as assuming specific registers get allocated for variables and 
used in an asm.  If we change the optimizer, we can "change the meaning
of programs written to work with GCC".

    We cannot do this without a very good reason.  Generating more
    efficient code is definitely not good enough.

Sure it is.  The alias set implementation is a perfectly good example: there
are numerous erroneous programs that have "worked" and will no longer work
once we made this change.