Implement this as it is done on GCC:
__float128 a, b, c, d; a = __builtin_fmaf128_round_to_odd (b, c, d); // generates xsmaddqpo a = __builtin_fmaf128_round_to_odd (b, c, -d); // generates xsmsubqpo a = - __builtin_fmaf128_round_to_odd (b, c, d); // generates xsnmaddqpo a = - __builtin_fmaf128_round_to_odd (b, c, -d); // generates xsnmsubpqp