I remember that coyote gulch did some benchmarks of gcc compilers with different flags. He tried a genetic algorithm type approach to try and find the "perfect" set of optimization flags to use.
His site is probably permanently down. I found some people had it cached and mirrored. http://geckies.user.cis.ksu.edu/tiki-view_cache.php?url=http://www.coyotegul... Acovea: Analysis of Compiler Options via Evolutionary Algorithm by Scott Robert Ladd .