Thus far the only software that hasn’t behaved as expected when recompiled with the
-O3 -march=pentium3 -pipe -ffast-math -frame-omit-pointer CFLAGS has been Firefox. I had to recompile it last night with the old, safe CFLAGS because the “overoptimized” version just spun circles in the background, never appearing and never doing anything but eating processor time.
I don’t have any theories on why it didn’t work, although it’s possible that it’s just on one machine that it seems to fail. Of course, it could be that Firefox’s code is so gnarled and bloated that overoptimizing it causes a collision of realities — like the immovable object and the irresistible force. Gee, I didn’t know I had tempted destruction so blithely. ;)