It produces a program.l and program.m file which describes the optimizations implemented and gives the altered source code, respectively. The command line option only writes these files if explicitly told to do so. There are many fine-tuning options for pfa, but the most important concerns the level one cache size. The compiler has many performance enhancing options as well, many of which concern memory management techniques. For small jobs, the memory management defaults are satisfactory, but for larger jobs some custom tuning will probably be necessary.
All jobs benefit from including the optimization options such as -Ofast.
This is an option group that includes SGI's choices of the best optimization routines and is a good place to start. With a little experience, some of the other options can be explored that may enhance performance even more. Another concern, especially for users coming from the Cray Y-MP environment, concerns the handling of floating point exceptions. The Origin 2000 is IEEE compliant in this area, meaning that by default it ignores floating point exceptions so your end results could end up being meaningless. As this command line tends to get longer and longer, I suggest putting it in your .cshrc.local file, along with setting the environment to your choice of exception handling routines.