Certain functions such as objc_autoreleaseReturnValue have to be called as
tail-calls even at -O0. Since normal fast-isel doesn't emit calls as tail calls,
we have to fall back to SelectionDAG to select calls that are marked as tail.
<rdar://problem/17991614>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215600 91177308-0d34-0410-b5e6-96231b3b80d8
