[calloc]

Still has nothing to do with choosing LLVM over GCC. Currently GCC is happily generating object files for me that contains i386, x86_64, and ppc:

file x.o x.o: Mach-O universal binary with 2 architectures

x.o (for architecture i386): Mach-O object i386

x.o (for architecture x86_64): Mach-O 64-bit object x86_64

x.o (for architecture ppc7400): Mach-O object ppc

Going to another architecture doesn't mean changing the compiler at all, just like they didn't change the compiler when going from PowerPC to Intel. Back on PowerPC it was GCC and now on Intel it is GCC. I believe that GCC is also used to compile for the iPhone/iPad.

Please don't get me wrong, I am really happy Apple is embracing LLVM with the various tools surrounding it and is moving away from GCC, however that is not a sign that they are planning on moving CPU architectures again.