Supported CPUs in Clang

I’m testing Clang/LLVM on FreeBSD 9 and was wondering what CPU optimization options are available. I read the man page and have done other research and see that you can set this by using the -march flag, but I haven’t been able to find a list of what -march options are available for the i386/x86_64 architectures. For example, my computer has an AMD Athlon II X4 processor, and in GCC the flag for this would be “amdfam10.” Could someone point me to a list of supported options?