FreeBSD supports 32- and 64-bit x86, arm, mips, and powerpc, as well as sparc64. We intend to use Clang as the system compiler across supported architectures, and are either using it now or are close for architectures other than mips and sparc64. This bug will depend on those issues that prevent us from enabling Clang as the FreeBSD/mips system compiler.
We use Clang/LLVM/LLD as the system tool chain on all supported FreeBSD targets now. Depends-on issues have all been resolved or worked around. Three issues (PR25176, PR34391, PR34604) are still open and have been moved to the see-also list here.