f77 performance under 3.3.1

[Wayne Podaima]

We have some unhappy observations re performance of Fortran programs under
IRIX 3.3.1.  The same program compiled under 3.3.1 runs about 5% slower
than it did under 3.2.3 (same compiler options), using 1 cpu of a 4D/240S.
The program is compute intensive - no paging, no disk I/O, double precision.
Any ideas; anyone with similar results?

We then tried the libfpe.a floating point exception handling library,
expecting it to be still slower; well it ran 2% FASTER than the original
3.2.3 compiled version.  What gives?

Any comments appreciated,
  Wayne Podaima