text: /*
   *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS.  All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
  
  #ifdef WEBRTC_ARCH_ARM_FAMILY
  
  #include <arm_neon.h>
  
  static inline void DotProductWithScaleNeon(int32_t* cross_correlation,
                                             const int16_t* vector1,
                                             const int16_t* vector2,
                                             size_t length,
                                             int scaling) {
    size_t i = 0;
    size_t len1 = length >> 3;
    size_t len2 = length & 7;
    int64x2_t sum0 = vdupq_n_s64(0);
    int64x2_t sum1 = vdupq_n_s64(0);
  
    for (i = len1; i > 0; i -= 1) {
      int16x8_t seq1_16x8 = vld1q_s16(vector1);
      int16x8_t seq2_16x8 = vld1q_s16(vector2);
  #if defined(WEBRTC_ARCH_ARM64)
      int32x4_t tmp0 = vmull_s16(vget_low_s16(seq1_16x8),
                                 vget_low_s16(seq2_16x8));
      int32x4_t tmp1 = vmull_high_s16(seq1_16x8, seq2_16x8);
  #else
      int32x4_t tmp0 = vmull_s16(vget_low_s16(seq1_16x8),
                                 vget_low_s16(seq2_16x8));
      int32x4_t tmp1 = vmull_s16(vget_high_s16(seq1_16x8),
                                 vget_high_s16(seq2_16x8));
  #endif
      sum0 = vpadalq_s32(sum0, tmp0);
      sum1 = vpadalq_s32(sum1, tmp1);
      vector1 += 8;
      vector2 += 8;
    }
  
    // Calculate the rest of the samples.
    int64_t sum_res = 0;
    for (i = len2; i > 0; i -= 1) {
      sum_res += WEBRTC_SPL_MUL_16_16(*vector1, *vector2);
      vector1++;
      vector2++;
    }
  
    sum0 = vaddq_s64(sum0, sum1);
  #if defined(WEBRTC_ARCH_ARM64)
    int64_t sum2 = vaddvq_s64(sum0);
    *cross_correlation = (int32_t)((sum2 + sum_res) >> scaling);
  #else
    int64x1_t shift = vdup_n_s64(-scaling);
    int64x1_t sum2 = vadd_s64(vget_low_s64(sum0), vget_high_s64(sum0));
    sum2 = vadd_s64(sum2, vdup_n_s64(sum_res));
    sum2 = vshl_s64(sum2, shift);
    vst1_lane_s32(cross_correlation, vreinterpret_s32_s64(sum2), 0);
  #endif
  }
  
  /* NEON version of WebRtcSpl_CrossCorrelation() for ARM32/64 platforms. */
  void WebRtcSpl_CrossCorrelationNeon(int32_t* cross_correlation,
                                      const int16_t* seq1,
                                      const int16_t* seq2,
                                      size_t dim_seq,
                                      size_t dim_cross_correlation,
                                      int right_shifts,
                                      int step_seq2) {
    size_t i = 0;
  
    for (i = 0; i < dim_cross_correlation; i++) {
      const int16_t* seq1_ptr = seq1;
      const int16_t* seq2_ptr = seq2 + (step_seq2 * i);
  
      DotProductWithScaleNeon(cross_correlation,
                              seq1_ptr,
                              seq2_ptr,
                              dim_seq,
                              right_shifts);
      cross_correlation++;
    }
  }
  
  #endif // WEBRTC_ARCH_ARM_FAMILY
  