Re: underflows, overflows, ... [on Alphas]

[Craig Burley <burley at gnu dot org>]

>When the code comes to the first floating point it cores dump. can't run
>the code anymore.
>
>Whereas with digital fortran I only need to enable the flag -fpe2 and
>things run nicely.

For now, it seems that at least two things have to happen:

  1.  You have to compile all your code with the -mieee option.

  2.  You have to link to libraries (e.g. libf2c) that have been
      compiled with the -mieee option as well.

The former you can do easily enough, but the latter requires knowing
how to build g77 (egcs) accordingly, at least for now.

In the future we hope to provide an automatic means to link to the
appropriate library routines.  This will probably mean #2 will
become "you have to link all your code using the -mieee option",
which means "g77 -mieee foo.f bar.f" would be enough to get what
is needed.

Doing this will at least require something called "multi-libbing"
the version of libf2c shipped with egcs-g77.  I'm hoping we can
accomplish this for egcs version 1.2.  Ideally we'd set it up so
if you compiled with -mieee, any library calls in the generated code
would automatically pick up the corresponding libf2c routines
compiled with -mieee, but for now that sort of solution (used by at
least some Fortran vendors, I believe) seems to be outside of
the architectural scope of egcs.

        tq vm, (burley)