There’s been a number of commits lately around higher optimization levels for your DragonFly kernel. It looks you can even set it systemwide. Boot code remains at -O; any higher level will make it explode. Is this safe? I have no idea!
A running description of activity related to DragonFly BSD.
That’s GCC stuff. Even -O can be dangerous in some cases (but I’ve seen it last time on gcc 4.x). On the other hand clang since 3.6 (probably) is quite safe even on -O3. Tested on my FreeBSD servers.