Performance loss from RedHat 7.0 to RedHat 9.0

[Jean-Marc Petit <petit at obs-besancon dot fr>]

Hello,

I just noticed a strong decrease of efficiency in code produced by G77 
when moving from the RedHat 7.0 version (can't recall the version, it's no 
longer on my computer) to RedHat 9.0. In both cases, the program works 
fine, and give the correct result. It has run with G77 on RH70 and RH90, 
f2c on RH70, G77 on Suse 8.0, PGF77 (PGI's Fortran compiler) on Suse 8.0 
and Intel Fortran 8.0 (ifc or now ifort) on RH90. G77 used to give an 
efficient code that was running at speed comparable to commercial Fortran, 
but on the RH90 release, it has slowed by almost a factor of 2.

Hardware: Athlon 1.0GHz, 512 MB RAM

RedHat 7.0:

compiler command: g77 -u -O3 -ffastmath -funroll-loops -m486 -o bench bench.f

result of the "time" command:

real    0m37.415s
user    0m36.890s
sys     0m0.000s


RedHat 9.0:

g77 -v gives: gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)

compiler command: g77 -u -O3 -fno-automatic -funroll-loops -malign-double 
-march=athlon -ffast-math -o bench bench.f

(this is my best case)

result of the "time" comand:

real    1m1.855s
user    1m1.740s
sys     0m0.000s


Is that a known behaviour ? Is there something obvious I can do to make 
things better ? I'd hate to be forced into using Intel Fortran Compiler.

By the way, Interl Fortran Compiler executiion time is:

real    0m26.749s
user    0m26.280s
sys     0m0.010s


Another problem with this version of GCC/G77: I have an old version of f2c 
(VERSION 19990503) that used to work on RedHat 7.0, and complains now on 
RedHat 9.0. I can compile it, and run it, but it can't link the programs, 
complaining about an undefined reference:

undefined reference to `MAIN__'

although my environment variables are (I think) correctly set. Is there 
something new in GCC/G77 that imposes to go to a newer version of f2c ?

Thank you for the time you'll spend on my questions, sincerely,

Jean-Marc Petit