> While I don't consider missed optimisations bugs as such, they are easy to find. Simply compile some non-trivial function and look at the output.

Perhaps you'll give me a little credit :) if I mention that I found missed optimization bugs in extremely trivial functions. One of them involved gcc generating several completely useless stores even at -O3: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44194