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

#include "common.h"

static inline __m128i rsp_vmadl_vmudl(uint32_t iw, __m128i vs, __m128i vt,
  __m128i zero, __m128i *acc_lo, __m128i *acc_md, __m128i *acc_hi) {
  __m128i hi, overflow_mask;

  hi = _mm_mulhi_epu16(vs, vt); 

  // VMADL
  if (iw & 0x8) {

    // Tricky part: start accumulate everything.
    // Get/keep the carry as we'll add it in later.
    overflow_mask = _mm_adds_epu16(*acc_lo, hi); 
    *acc_lo = _mm_add_epi16(*acc_lo, hi); 

    overflow_mask = _mm_cmpeq_epi16(*acc_lo, overflow_mask);
    overflow_mask = _mm_cmpeq_epi16(overflow_mask, zero);
    hi = _mm_sub_epi16(zero, overflow_mask);

    // Check for overflow of the upper sum.
    //
    // TODO: Since hi can only be {0,1}, we should
    // be able to generalize this for performance.
    overflow_mask = _mm_adds_epu16(*acc_md, hi); 
    *acc_md = _mm_add_epi16(*acc_md, hi); 

    overflow_mask = _mm_cmpeq_epi16(*acc_md, overflow_mask);
    overflow_mask = _mm_cmpeq_epi16(overflow_mask, zero);

    // Finish up the accumulation of the... accumulator.
    // Since the product was unsigned, only worry about
    // positive overflow (i.e.: borrowing not possible).
    *acc_hi = _mm_sub_epi16(*acc_hi, overflow_mask);

    return rsp_uclamp_acc(*acc_lo, *acc_md, *acc_hi, zero);
  }

  // VMUDL
  else {
    *acc_lo = hi;
    *acc_md = zero;
    *acc_hi = zero;

    return hi;
  }
}