Hi, I've managed to get our GENERIC kernel to compile with llvm/clang. There is still one temporary fix (at least until clang guys fix the related bug), but the kernel definitely compiles, boots and works stable. As a stress test I've done a buildworld, which it survived without problems. I've put everything about DragonFly and llvm/clang so far together on one page, http://leaf.dragonflybsd.org/~alexh/clang/clang.html in case you are interested in details or even want to try it yourself.
Sincerely, Alex