Pull in r244063 from upstream clang trunk (by James Y Knight):
Add missing atomic libcall support.
Support for emitting libcalls for __atomic_fetch_nand and
__atomic_{add,sub,and,or,xor,nand}_fetch was missing; add it, and some
test cases.
Differential Revision: http://reviews.llvm.org/D10847This fixes "cannot compile this atomic library call yet" errors when
compiling code which calls the above builtins, on arm < v6.