argument.  This avoids the argument from being silenced when the argument is
the NULL macro, which is defined in a system header.  This also makes the output
a bit nicer, e.g.:

t.c:8:3: warning: null passed to a callee which requires a non-null argument
  func1(NULL, cp2, i1);
  ^     ~~~~

vs something like:

t.c:8:10: warning: argument is null where non-null is required
  func1(NULL, cp2, i1);
        ^

llvm-svn: 72393