/*
 * Copyright (c) 2014 The WebM project authors. All rights reserved.
 * Copyright (c) 2023, Alliance for Open Media. All rights reserved.
 *
 * This source code is subject to the terms of the BSD 2 Clause License and
 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
 * was not distributed with this source code in the LICENSE file, you can
 * obtain it at www.aomedia.org/license/software. If the Alliance for Open
 * Media Patent License 1.0 was not distributed with this source code in the
 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
 */

#include <arm_neon.h>
#include <assert.h>
#include <string.h>

#include "config/aom_config.h"

#include "aom/aom_integer.h"
#include "aom_dsp/aom_dsp_common.h"
#include "aom_dsp/aom_filter.h"
#include "aom_dsp/arm/aom_convolve8_neon.h"
#include "aom_dsp/arm/aom_filter.h"
#include "aom_dsp/arm/mem_neon.h"
#include "aom_dsp/arm/transpose_neon.h"
#include "aom_ports/mem.h"

DECLARE_ALIGNED(16, static const uint8_t, kMatMulPermuteTbl[32]) = {
  // clang-format off
  0,  1,  2,  3,  4,  5,  6,  7,  2,  3,  4,  5,  6,  7,  8,  9,
  4,  5,  6,  7,  8,  9, 10, 11,  6,  7,  8,  9, 10, 11, 12, 13
  // clang-format on
};

DECLARE_ALIGNED(16, static const uint8_t, kDotProdPermuteTbl[48]) = {
  0, 1, 2,  3,  1, 2,  3,  4,  2,  3,  4,  5,  3,  4,  5,  6,
  4, 5, 6,  7,  5, 6,  7,  8,  6,  7,  8,  9,  7,  8,  9,  10,
  8, 9, 10, 11, 9, 10, 11, 12, 10, 11, 12, 13, 11, 12, 13, 14
};

DECLARE_ALIGNED(16, static const uint8_t, kDotProdMergeBlockTbl[48]) = {
  // Shift left and insert new last column in transposed 4x4 block.
  1, 2, 3, 16, 5, 6, 7, 20, 9, 10, 11, 24, 13, 14, 15, 28,
  // Shift left and insert two new columns in transposed 4x4 block.
  2, 3, 16, 17, 6, 7, 20, 21, 10, 11, 24, 25, 14, 15, 28, 29,
  // Shift left and insert three new columns in transposed 4x4 block.
  3, 16, 17, 18, 7, 20, 21, 22, 11, 24, 25, 26, 15, 28, 29, 30
};

static inline int16x4_t convolve8_4_h(const uint8x16_t samples,
                                      const int8x8_t filters,
                                      const uint8x16x2_t permute_tbl) {
  // Permute samples ready for dot product.
  // { 0,  1,  2,  3,  1,  2,  3,  4,  2,  3,  4,  5,  3,  4,  5,  6 }
  // { 4,  5,  6,  7,  5,  6,  7,  8,  6,  7,  8,  9,  7,  8,  9, 10 }
  uint8x16_t permuted_samples[2] = { vqtbl1q_u8(samples, permute_tbl.val[0]),
                                     vqtbl1q_u8(samples, permute_tbl.val[1]) };

  int32x4_t sum =
      vusdotq_lane_s32(vdupq_n_s32(0), permuted_samples[0], filters, 0);
  sum = vusdotq_lane_s32(sum, permuted_samples[1], filters, 1);

  // Further narrowing and packing is performed by the caller.
  return vmovn_s32(sum);
}

static inline uint8x8_t convolve8_8_h(const uint8x16_t samples,
                                      const int8x8_t filters,
                                      const uint8x16x3_t permute_tbl) {
  // Permute samples ready for dot product.
  // { 0,  1,  2,  3,  1,  2,  3,  4,  2,  3,  4,  5,  3,  4,  5,  6 }
  // { 4,  5,  6,  7,  5,  6,  7,  8,  6,  7,  8,  9,  7,  8,  9, 10 }
  // { 8,  9, 10, 11,  9, 10, 11, 12, 10, 11, 12, 13, 11, 12, 13, 14 }
  uint8x16_t permuted_samples[3] = { vqtbl1q_u8(samples, permute_tbl.val[0]),
                                     vqtbl1q_u8(samples, permute_tbl.val[1]),
                                     vqtbl1q_u8(samples, permute_tbl.val[2]) };

  // First 4 output values.
  int32x4_t sum0 =
      vusdotq_lane_s32(vdupq_n_s32(0), permuted_samples[0], filters, 0);
  sum0 = vusdotq_lane_s32(sum0, permuted_samples[1], filters, 1);
  // Second 4 output values.
  int32x4_t sum1 =
      vusdotq_lane_s32(vdupq_n_s32(0), permuted_samples[1], filters, 0);
  sum1 = vusdotq_lane_s32(sum1, permuted_samples[2], filters, 1);

  // Narrow and re-pack.
  int16x8_t sum = vcombine_s16(vmovn_s32(sum0), vmovn_s32(sum1));
  // We halved the filter values so -1 from right shift.
  return vqrshrun_n_s16(sum, FILTER_BITS - 1);
}

static inline void convolve8_horiz_8tap_neon_i8mm(
    const uint8_t *src, ptrdiff_t src_stride, uint8_t *dst,
    ptrdiff_t dst_stride, const int16_t *filter_x, int w, int h) {
  // Filter values are even, so halve to reduce intermediate precision reqs.
  const int8x8_t filter = vshrn_n_s16(vld1q_s16(filter_x), 1);

  if (w == 4) {
    const uint8x16x2_t perm_tbl = vld1q_u8_x2(kDotProdPermuteTbl);
    do {
      uint8x16_t s0, s1, s2, s3;
      load_u8_16x4(src, src_stride, &s0, &s1, &s2, &s3);

      int16x4_t d0 = convolve8_4_h(s0, filter, perm_tbl);
      int16x4_t d1 = convolve8_4_h(s1, filter, perm_tbl);
      int16x4_t d2 = convolve8_4_h(s2, filter, perm_tbl);
      int16x4_t d3 = convolve8_4_h(s3, filter, perm_tbl);
      // We halved the filter values so -1 from right shift.
      uint8x8_t d01 = vqrshrun_n_s16(vcombine_s16(d0, d1), FILTER_BITS - 1);
      uint8x8_t d23 = vqrshrun_n_s16(vcombine_s16(d2, d3), FILTER_BITS - 1);

      store_u8x4_strided_x2(dst + 0 * dst_stride, dst_stride, d01);
      store_u8x4_strided_x2(dst + 2 * dst_stride, dst_stride, d23);

      src += 4 * src_stride;
      dst += 4 * dst_stride;
      h -= 4;
    } while (h > 0);
  } else {
    const uint8x16x3_t perm_tbl = vld1q_u8_x3(kDotProdPermuteTbl);

    do {
      int width = w;
      const uint8_t *s = src;
      uint8_t *d = dst;
      do {
        uint8x16_t s0, s1, s2, s3;
        load_u8_16x4(s, src_stride, &s0, &s1, &s2, &s3);

        uint8x8_t d0 = convolve8_8_h(s0, filter, perm_tbl);
        uint8x8_t d1 = convolve8_8_h(s1, filter, perm_tbl);
        uint8x8_t d2 = convolve8_8_h(s2, filter, perm_tbl);
        uint8x8_t d3 = convolve8_8_h(s3, filter, perm_tbl);

        store_u8_8x4(d, dst_stride, d0, d1, d2, d3);

        s += 8;
        d += 8;
        width -= 8;
      } while (width != 0);
      src += 4 * src_stride;
      dst += 4 * dst_stride;
      h -= 4;
    } while (h > 0);
  }
}

static inline int16x4_t convolve6_4_h(const uint8x16_t samples,
                                      const int8x16_t filter,
                                      const uint8x16_t permute_tbl) {
  // Permute samples ready for matrix multiply.
  // { 0,  1,  2,  3,  4,  5,  6,  7,  2,  3,  4,  5,  6,  7,  8,  9 }
  uint8x16_t perm_samples = vqtbl1q_u8(samples, permute_tbl);

  // These instructions multiply a 2x8 matrix (samples) by an 8x2 matrix
  // (filter), destructively accumulating into the destination register.
  int32x4_t sum = vusmmlaq_s32(vdupq_n_s32(0), perm_samples, filter);

  // Further narrowing and packing is performed by the caller.
  return vmovn_s32(sum);
}

static inline uint8x8_t convolve6_8_h(const uint8x16_t samples,
                                      const int8x16_t filter,
                                      const uint8x16x2_t permute_tbl) {
  // Permute samples ready for matrix multiply.
  // { 0,  1,  2,  3,  4,  5,  6,  7,  2,  3,  4,  5,  6,  7,  8,  9 }
  // { 4,  5,  6,  7,  8,  9, 10, 11,  6,  7,  8,  9, 10, 11, 12, 13 }
  uint8x16_t perm_samples[2] = { vqtbl1q_u8(samples, permute_tbl.val[0]),
                                 vqtbl1q_u8(samples, permute_tbl.val[1]) };

  // These instructions multiply a 2x8 matrix (samples) by an 8x2 matrix
  // (filter), destructively accumulating into the destination register.
  int32x4_t sum0123 = vusmmlaq_s32(vdupq_n_s32(0), perm_samples[0], filter);
  int32x4_t sum4567 = vusmmlaq_s32(vdupq_n_s32(0), perm_samples[1], filter);

  // Narrow and re-pack.
  int16x8_t sum = vcombine_s16(vmovn_s32(sum0123), vmovn_s32(sum4567));
  // We halved the filter values so -1 from right shift.
  return vqrshrun_n_s16(sum, FILTER_BITS - 1);
}

static inline void convolve8_horiz_6tap_neon_i8mm(
    const uint8_t *src, ptrdiff_t src_stride, uint8_t *dst,
    ptrdiff_t dst_stride, const int16_t *filter_x, int width, int height) {
  // Filter values are even, so halve to reduce intermediate precision reqs.
  const int8x8_t x_filter = vshrn_n_s16(vld1q_s16(filter_x), 1);
  // Stagger the filter for use with the matrix multiply instructions.
  // { f0, f1, f2, f3, f4, f5,  0,  0,  0, f0, f1, f2, f3, f4, f5,  0 }
  const int8x16_t filter =
      vcombine_s8(vext_s8(x_filter, x_filter, 1), x_filter);

  if (width == 4) {
    const uint8x16_t perm_tbl = vld1q_u8(kMatMulPermuteTbl);
    do {
      uint8x16_t s0, s1, s2, s3;
      load_u8_16x4(src, src_stride, &s0, &s1, &s2, &s3);

      int16x4_t t0 = convolve6_4_h(s0, filter, perm_tbl);
      int16x4_t t1 = convolve6_4_h(s1, filter, perm_tbl);
      int16x4_t t2 = convolve6_4_h(s2, filter, perm_tbl);
      int16x4_t t3 = convolve6_4_h(s3, filter, perm_tbl);
      // We halved the filter values so -1 from right shift.
      uint8x8_t d01 = vqrshrun_n_s16(vcombine_s16(t0, t1), FILTER_BITS - 1);
      uint8x8_t d23 = vqrshrun_n_s16(vcombine_s16(t2, t3), FILTER_BITS - 1);

      store_u8x4_strided_x2(dst + 0 * dst_stride, dst_stride, d01);
      store_u8x4_strided_x2(dst + 2 * dst_stride, dst_stride, d23);

      src += 4 * src_stride;
      dst += 4 * dst_stride;
      height -= 4;
    } while (height > 0);
  } else {
    const uint8x16x2_t perm_tbl = vld1q_u8_x2(kMatMulPermuteTbl);

    do {
      int w = width;
      const uint8_t *s = src;
      uint8_t *d = dst;
      do {
        uint8x16_t s0, s1, s2, s3;
        load_u8_16x4(s, src_stride, &s0, &s1, &s2, &s3);

        uint8x8_t d0 = convolve6_8_h(s0, filter, perm_tbl);
        uint8x8_t d1 = convolve6_8_h(s1, filter, perm_tbl);
        uint8x8_t d2 = convolve6_8_h(s2, filter, perm_tbl);
        uint8x8_t d3 = convolve6_8_h(s3, filter, perm_tbl);

        store_u8_8x4(d, dst_stride, d0, d1, d2, d3);

        s += 8;
        d += 8;
        w -= 8;
      } while (w != 0);
      src += 4 * src_stride;
      dst += 4 * dst_stride;
      height -= 4;
    } while (height > 0);
  }
}

void aom_convolve8_horiz_neon_i8mm(const uint8_t *src, ptrdiff_t src_stride,
                                   uint8_t *dst, ptrdiff_t dst_stride,
                                   const int16_t *filter_x, int x_step_q4,
                                   const int16_t *filter_y, int y_step_q4,
                                   int w, int h) {
  assert((intptr_t)dst % 4 == 0);
  assert(dst_stride % 4 == 0);

  (void)x_step_q4;
  (void)filter_y;
  (void)y_step_q4;

  src -= ((SUBPEL_TAPS / 2) - 1);

  int filter_taps = get_filter_taps_convolve8(filter_x);

  if (filter_taps == 2) {
    convolve8_horiz_2tap_neon(src + 3, src_stride, dst, dst_stride, filter_x, w,
                              h);
  } else if (filter_taps <= 6) {
    convolve8_horiz_6tap_neon_i8mm(src + 1, src_stride, dst, dst_stride,
                                   filter_x, w, h);
  } else {
    convolve8_horiz_8tap_neon_i8mm(src, src_stride, dst, dst_stride, filter_x,
                                   w, h);
  }
}

static inline void transpose_concat_4x4(uint8x8_t a0, uint8x8_t a1,
                                        uint8x8_t a2, uint8x8_t a3,
                                        uint8x16_t *b) {
  // Transpose 8-bit elements and concatenate result rows as follows:
  // a0: 00, 01, 02, 03, XX, XX, XX, XX
  // a1: 10, 11, 12, 13, XX, XX, XX, XX
  // a2: 20, 21, 22, 23, XX, XX, XX, XX
  // a3: 30, 31, 32, 33, XX, XX, XX, XX
  //
  // b: 00, 10, 20, 30, 01, 11, 21, 31, 02, 12, 22, 32, 03, 13, 23, 33

  uint8x16_t a0q = vcombine_u8(a0, vdup_n_u8(0));
  uint8x16_t a1q = vcombine_u8(a1, vdup_n_u8(0));
  uint8x16_t a2q = vcombine_u8(a2, vdup_n_u8(0));
  uint8x16_t a3q = vcombine_u8(a3, vdup_n_u8(0));

  uint8x16_t a01 = vzipq_u8(a0q, a1q).val[0];
  uint8x16_t a23 = vzipq_u8(a2q, a3q).val[0];

  uint16x8_t a0123 =
      vzipq_u16(vreinterpretq_u16_u8(a01), vreinterpretq_u16_u8(a23)).val[0];

  *b = vreinterpretq_u8_u16(a0123);
}

static inline void transpose_concat_8x4(uint8x8_t a0, uint8x8_t a1,
                                        uint8x8_t a2, uint8x8_t a3,
                                        uint8x16_t *b0, uint8x16_t *b1) {
  // Transpose 8-bit elements and concatenate result rows as follows:
  // a0: 00, 01, 02, 03, 04, 05, 06, 07
  // a1: 10, 11, 12, 13, 14, 15, 16, 17
  // a2: 20, 21, 22, 23, 24, 25, 26, 27
  // a3: 30, 31, 32, 33, 34, 35, 36, 37
  //
  // b0: 00, 10, 20, 30, 01, 11, 21, 31, 02, 12, 22, 32, 03, 13, 23, 33
  // b1: 04, 14, 24, 34, 05, 15, 25, 35, 06, 16, 26, 36, 07, 17, 27, 37

  uint8x16_t a0q = vcombine_u8(a0, vdup_n_u8(0));
  uint8x16_t a1q = vcombine_u8(a1, vdup_n_u8(0));
  uint8x16_t a2q = vcombine_u8(a2, vdup_n_u8(0));
  uint8x16_t a3q = vcombine_u8(a3, vdup_n_u8(0));

  uint8x16_t a01 = vzipq_u8(a0q, a1q).val[0];
  uint8x16_t a23 = vzipq_u8(a2q, a3q).val[0];

  uint16x8x2_t a0123 =
      vzipq_u16(vreinterpretq_u16_u8(a01), vreinterpretq_u16_u8(a23));

  *b0 = vreinterpretq_u8_u16(a0123.val[0]);
  *b1 = vreinterpretq_u8_u16(a0123.val[1]);
}

static inline int16x4_t convolve8_4_v(const uint8x16_t samples_lo,
                                      const uint8x16_t samples_hi,
                                      const int8x8_t filters) {
  // Sample permutation is performed by the caller.
  int32x4_t sum = vusdotq_lane_s32(vdupq_n_s32(0), samples_lo, filters, 0);
  sum = vusdotq_lane_s32(sum, samples_hi, filters, 1);

  // Further narrowing and packing is performed by the caller.
  return vmovn_s32(sum);
}

static inline uint8x8_t convolve8_8_v(const uint8x16_t samples0_lo,
                                      const uint8x16_t samples0_hi,
                                      const uint8x16_t samples1_lo,
                                      const uint8x16_t samples1_hi,
                                      const int8x8_t filters) {
  // Sample permutation is performed by the caller.

  // First 4 output values.
  int32x4_t sum0 = vusdotq_lane_s32(vdupq_n_s32(0), samples0_lo, filters, 0);
  sum0 = vusdotq_lane_s32(sum0, samples0_hi, filters, 1);
  // Second 4 output values.
  int32x4_t sum1 = vusdotq_lane_s32(vdupq_n_s32(0), samples1_lo, filters, 0);
  sum1 = vusdotq_lane_s32(sum1, samples1_hi, filters, 1);

  // Narrow and re-pack.
  int16x8_t sum = vcombine_s16(vmovn_s32(sum0), vmovn_s32(sum1));
  // We halved the filter values so -1 from right shift.
  return vqrshrun_n_s16(sum, FILTER_BITS - 1);
}

static inline void convolve8_vert_8tap_neon_i8mm(
    const uint8_t *src, ptrdiff_t src_stride, uint8_t *dst,
    ptrdiff_t dst_stride, const int16_t *filter_y, int w, int h) {
  // Filter values are even, so halve to reduce intermediate precision reqs.
  const int8x8_t filter = vshrn_n_s16(vld1q_s16(filter_y), 1);
  const uint8x16x3_t merge_block_tbl = vld1q_u8_x3(kDotProdMergeBlockTbl);
  uint8x16x2_t samples_LUT;

  if (w == 4) {
    uint8x8_t s0, s1, s2, s3, s4, s5, s6;
    load_u8_8x7(src, src_stride, &s0, &s1, &s2, &s3, &s4, &s5, &s6);
    src += 7 * src_stride;

    // This operation combines a conventional transpose and the sample permute
    // (see horizontal case) required before computing the dot product.
    uint8x16_t s0123, s1234, s2345, s3456;
    transpose_concat_4x4(s0, s1, s2, s3, &s0123);
    transpose_concat_4x4(s1, s2, s3, s4, &s1234);
    transpose_concat_4x4(s2, s3, s4, s5, &s2345);
    transpose_concat_4x4(s3, s4, s5, s6, &s3456);

    do {
      uint8x8_t s7, s8, s9, s10;
      load_u8_8x4(src, src_stride, &s7, &s8, &s9, &s10);

      uint8x16_t s4567, s5678, s6789, s78910;
      transpose_concat_4x4(s7, s8, s9, s10, &s78910);

      // Merge new data into block from previous iteration.
      samples_LUT.val[0] = s3456;
      samples_LUT.val[1] = s78910;
      s4567 = vqtbl2q_u8(samples_LUT, merge_block_tbl.val[0]);
      s5678 = vqtbl2q_u8(samples_LUT, merge_block_tbl.val[1]);
      s6789 = vqtbl2q_u8(samples_LUT, merge_block_tbl.val[2]);

      int16x4_t d0 = convolve8_4_v(s0123, s4567, filter);
      int16x4_t d1 = convolve8_4_v(s1234, s5678, filter);
      int16x4_t d2 = convolve8_4_v(s2345, s6789, filter);
      int16x4_t d3 = convolve8_4_v(s3456, s78910, filter);
      // We halved the filter values so -1 from right shift.
      uint8x8_t d01 = vqrshrun_n_s16(vcombine_s16(d0, d1), FILTER_BITS - 1);
      uint8x8_t d23 = vqrshrun_n_s16(vcombine_s16(d2, d3), FILTER_BITS - 1);

      store_u8x4_strided_x2(dst + 0 * dst_stride, dst_stride, d01);
      store_u8x4_strided_x2(dst + 2 * dst_stride, dst_stride, d23);

      // Prepare block for next iteration - re-using as much as possible.
      // Shuffle everything up four rows.
      s0123 = s4567;
      s1234 = s5678;
      s2345 = s6789;
      s3456 = s78910;

      src += 4 * src_stride;
      dst += 4 * dst_stride;
      h -= 4;
    } while (h != 0);
  } else {
    do {
      int height = h;
      const uint8_t *s = src;
      uint8_t *d = dst;

      uint8x8_t s0, s1, s2, s3, s4, s5, s6;
      load_u8_8x7(s, src_stride, &s0, &s1, &s2, &s3, &s4, &s5, &s6);
      s += 7 * src_stride;

      // This operation combines a conventional transpose and the sample permute
      // (see horizontal case) required before computing the dot product.
      uint8x16_t s0123_lo, s0123_hi, s1234_lo, s1234_hi, s2345_lo, s2345_hi,
          s3456_lo, s3456_hi;
      transpose_concat_8x4(s0, s1, s2, s3, &s0123_lo, &s0123_hi);
      transpose_concat_8x4(s1, s2, s3, s4, &s1234_lo, &s1234_hi);
      transpose_concat_8x4(s2, s3, s4, s5, &s2345_lo, &s2345_hi);
      transpose_concat_8x4(s3, s4, s5, s6, &s3456_lo, &s3456_hi);

      do {
        uint8x8_t s7, s8, s9, s10;
        load_u8_8x4(s, src_stride, &s7, &s8, &s9, &s10);

        uint8x16_t s4567_lo, s4567_hi, s5678_lo, s5678_hi, s6789_lo, s6789_hi,
            s78910_lo, s78910_hi;
        transpose_concat_8x4(s7, s8, s9, s10, &s78910_lo, &s78910_hi);

        // Merge new data into block from previous iteration.
        samples_LUT.val[0] = s3456_lo;
        samples_LUT.val[1] = s78910_lo;
        s4567_lo = vqtbl2q_u8(samples_LUT, merge_block_tbl.val[0]);
        s5678_lo = vqtbl2q_u8(samples_LUT, merge_block_tbl.val[1]);
        s6789_lo = vqtbl2q_u8(samples_LUT, merge_block_tbl.val[2]);

        samples_LUT.val[0] = s3456_hi;
        samples_LUT.val[1] = s78910_hi;
        s4567_hi = vqtbl2q_u8(samples_LUT, merge_block_tbl.val[0]);
        s5678_hi = vqtbl2q_u8(samples_LUT, merge_block_tbl.val[1]);
        s6789_hi = vqtbl2q_u8(samples_LUT, merge_block_tbl.val[2]);

        uint8x8_t d0 =
            convolve8_8_v(s0123_lo, s4567_lo, s0123_hi, s4567_hi, filter);
        uint8x8_t d1 =
            convolve8_8_v(s1234_lo, s5678_lo, s1234_hi, s5678_hi, filter);
        uint8x8_t d2 =
            convolve8_8_v(s2345_lo, s6789_lo, s2345_hi, s6789_hi, filter);
        uint8x8_t d3 =
            convolve8_8_v(s3456_lo, s78910_lo, s3456_hi, s78910_hi, filter);

        store_u8_8x4(d, dst_stride, d0, d1, d2, d3);

        // Prepare block for next iteration - re-using as much as possible.
        // Shuffle everything up four rows.
        s0123_lo = s4567_lo;
        s0123_hi = s4567_hi;
        s1234_lo = s5678_lo;
        s1234_hi = s5678_hi;
        s2345_lo = s6789_lo;
        s2345_hi = s6789_hi;
        s3456_lo = s78910_lo;
        s3456_hi = s78910_hi;

        s += 4 * src_stride;
        d += 4 * dst_stride;
        height -= 4;
      } while (height != 0);
      src += 8;
      dst += 8;
      w -= 8;
    } while (w != 0);
  }
}

void aom_convolve8_vert_neon_i8mm(const uint8_t *src, ptrdiff_t src_stride,
                                  uint8_t *dst, ptrdiff_t dst_stride,
                                  const int16_t *filter_x, int x_step_q4,
                                  const int16_t *filter_y, int y_step_q4, int w,
                                  int h) {
  assert((intptr_t)dst % 4 == 0);
  assert(dst_stride % 4 == 0);

  (void)filter_x;
  (void)x_step_q4;
  (void)y_step_q4;

  src -= ((SUBPEL_TAPS / 2) - 1) * src_stride;

  int filter_taps = get_filter_taps_convolve8(filter_y);

  if (filter_taps == 2) {
    convolve8_vert_2tap_neon(src + 3 * src_stride, src_stride, dst, dst_stride,
                             filter_y, w, h);
  } else if (filter_taps == 4) {
    convolve8_vert_4tap_neon(src + 2 * src_stride, src_stride, dst, dst_stride,
                             filter_y, w, h);
  } else {
    convolve8_vert_8tap_neon_i8mm(src, src_stride, dst, dst_stride, filter_y, w,
                                  h);
  }
}