builtins.c (expand_builtin_compare_and_swap): If target is const0, don't pass the target to expand_atomic_compare_and_swap.

        * builtins.c (expand_builtin_compare_and_swap): If target is const0,
        don't pass the target to expand_atomic_compare_and_swap.
        (expand_builtin_atomic_compare_exchange): Likewise.

From-SVN: r181323