Going back to 2009, FreeBSD developers have worked to replace GCC with LLVM/Clang. Over time, there’s been numerous improvements especially with the FreeBSD 9.0 release. The FreeBSD developers are interested in doing away with the GPL-licensed GNU Compiler Collection and instead use the Apple-sponsored LLVM/Clang work that’s under a BSD-like license.

via [Phoronix] FreeBSD 10 To Use Clang Compiler, Deprecate GCC.