November 5th is Clang Day
docs.freebsd.org
docs.freebsd.org
[0] http://lists.cs.uiuc.edu/pipermail/llvmdev/2007-July/009817....
Apple doesn't want to use GPLv3 because of the patent clause.
It's a philosophy thing. The new provisions in the GPLv3 (principly the counter-tivoization requirements which prevent shipping integrated devices without reprogrammability) are seen as unacceptable to the FreeBSD team. So they simply ruled against the license, which means that recent versions of gcc are unusable and they need to look elsewhere for a modern compiler.
That's the official answer. The cynical answer is that they've always hated the FSF and their dependence on GNU software, and are finally jumping ship now that there's a non-copyleft compiler available for them to use.
But still, it's FreeBSD's distro, and they get to write the rules. And clang is a modern, attractive compiler. The feud may be dumb but the choice isn't.
http://unix.stackexchange.com/questions/49906/why-is-freebsd...
Also, the difference between GPL2 and GPL3 is large enough for many BSD backers to be of concern (the anti-Tivoisation clauses mean that one cannot close down firmware compiled with a GPL3'd version of gcc if it contains even the tiniest part of libc. Possibly, even using some of its macros in your code would be enough to require you to make your software GPL3. We won't know until this has been to court, but why take the risk?
"Apple shipped the Mac OS X 10.8 and iOS 6 releases, and they were built virtually entirely with Clang - llvm-gcc is obsolete."
Another interesting thing: "We invested major effort into compiler implementation and tuning for the custom Apple CPU design known as the "Apple A6". The exceptional CPU performance of the iPhone 5 was a result of a joint effort between the Apple silicon and LLVM teams."
The A6 quote doesn't mean much. All compilers work hard on device-specific optimizations; you can find similar press releases from Intel every few months.