//
// arch/x86_64/rsp/vsub.h
//
// This file is subject to the terms and conditions defined in
// 'LICENSE', which is part of this source code package.
//

static inline __m128i rsp_vsub(__m128i vs, __m128i vt,
  __m128i carry, __m128i *acc_lo) {
  __m128i unsat_diff, sat_diff, overflow, vd;

  // acc_lo uses saturated arithmetic.
  unsat_diff = _mm_sub_epi16(vt, carry);
  sat_diff = _mm_subs_epi16(vt, carry);

  *acc_lo = _mm_sub_epi16(vs, unsat_diff);
  vd = _mm_subs_epi16(vs, sat_diff);

  // VD is the signed diff of the two sources and the carry. Since we
  // have to saturate the diff of all three, we have to be clever.
  overflow = _mm_cmpgt_epi16(sat_diff, unsat_diff);
  return _mm_adds_epi16(vd, overflow);
}

