shithub: libvpx

ref: f62dcc9c334eb5060293cbf0cfd7de82bb4ea78c
dir: /vp9/common/arm/neon/vp9_iht8x8_add_neon.c/

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/*
 *  Copyright (c) 2014 The WebM 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 <arm_neon.h>
#include <assert.h>

#include "./vp9_rtcd.h"
#include "./vpx_config.h"
#include "vp9/common/vp9_common.h"
#include "vpx_dsp/arm/transpose_neon.h"

static int16_t cospi_2_64 = 16305;
static int16_t cospi_4_64 = 16069;
static int16_t cospi_6_64 = 15679;
static int16_t cospi_8_64 = 15137;
static int16_t cospi_10_64 = 14449;
static int16_t cospi_12_64 = 13623;
static int16_t cospi_14_64 = 12665;
static int16_t cospi_16_64 = 11585;
static int16_t cospi_18_64 = 10394;
static int16_t cospi_20_64 = 9102;
static int16_t cospi_22_64 = 7723;
static int16_t cospi_24_64 = 6270;
static int16_t cospi_26_64 = 4756;
static int16_t cospi_28_64 = 3196;
static int16_t cospi_30_64 = 1606;

static INLINE void IDCT8x8_1D(int16x8_t *q8s16, int16x8_t *q9s16,
                              int16x8_t *q10s16, int16x8_t *q11s16,
                              int16x8_t *q12s16, int16x8_t *q13s16,
                              int16x8_t *q14s16, int16x8_t *q15s16) {
  int16x4_t d0s16, d1s16, d2s16, d3s16;
  int16x4_t d8s16, d9s16, d10s16, d11s16, d12s16, d13s16, d14s16, d15s16;
  int16x4_t d16s16, d17s16, d18s16, d19s16, d20s16, d21s16, d22s16, d23s16;
  int16x4_t d24s16, d25s16, d26s16, d27s16, d28s16, d29s16, d30s16, d31s16;
  int16x8_t q0s16, q1s16, q2s16, q3s16, q4s16, q5s16, q6s16, q7s16;
  int32x4_t q2s32, q3s32, q5s32, q6s32, q8s32, q9s32;
  int32x4_t q10s32, q11s32, q12s32, q13s32, q15s32;

  d0s16 = vdup_n_s16(cospi_28_64);
  d1s16 = vdup_n_s16(cospi_4_64);
  d2s16 = vdup_n_s16(cospi_12_64);
  d3s16 = vdup_n_s16(cospi_20_64);

  d16s16 = vget_low_s16(*q8s16);
  d17s16 = vget_high_s16(*q8s16);
  d18s16 = vget_low_s16(*q9s16);
  d19s16 = vget_high_s16(*q9s16);
  d20s16 = vget_low_s16(*q10s16);
  d21s16 = vget_high_s16(*q10s16);
  d22s16 = vget_low_s16(*q11s16);
  d23s16 = vget_high_s16(*q11s16);
  d24s16 = vget_low_s16(*q12s16);
  d25s16 = vget_high_s16(*q12s16);
  d26s16 = vget_low_s16(*q13s16);
  d27s16 = vget_high_s16(*q13s16);
  d28s16 = vget_low_s16(*q14s16);
  d29s16 = vget_high_s16(*q14s16);
  d30s16 = vget_low_s16(*q15s16);
  d31s16 = vget_high_s16(*q15s16);

  q2s32 = vmull_s16(d18s16, d0s16);
  q3s32 = vmull_s16(d19s16, d0s16);
  q5s32 = vmull_s16(d26s16, d2s16);
  q6s32 = vmull_s16(d27s16, d2s16);

  q2s32 = vmlsl_s16(q2s32, d30s16, d1s16);
  q3s32 = vmlsl_s16(q3s32, d31s16, d1s16);
  q5s32 = vmlsl_s16(q5s32, d22s16, d3s16);
  q6s32 = vmlsl_s16(q6s32, d23s16, d3s16);

  d8s16 = vrshrn_n_s32(q2s32, 14);
  d9s16 = vrshrn_n_s32(q3s32, 14);
  d10s16 = vrshrn_n_s32(q5s32, 14);
  d11s16 = vrshrn_n_s32(q6s32, 14);
  q4s16 = vcombine_s16(d8s16, d9s16);
  q5s16 = vcombine_s16(d10s16, d11s16);

  q2s32 = vmull_s16(d18s16, d1s16);
  q3s32 = vmull_s16(d19s16, d1s16);
  q9s32 = vmull_s16(d26s16, d3s16);
  q13s32 = vmull_s16(d27s16, d3s16);

  q2s32 = vmlal_s16(q2s32, d30s16, d0s16);
  q3s32 = vmlal_s16(q3s32, d31s16, d0s16);
  q9s32 = vmlal_s16(q9s32, d22s16, d2s16);
  q13s32 = vmlal_s16(q13s32, d23s16, d2s16);

  d14s16 = vrshrn_n_s32(q2s32, 14);
  d15s16 = vrshrn_n_s32(q3s32, 14);
  d12s16 = vrshrn_n_s32(q9s32, 14);
  d13s16 = vrshrn_n_s32(q13s32, 14);
  q6s16 = vcombine_s16(d12s16, d13s16);
  q7s16 = vcombine_s16(d14s16, d15s16);

  d0s16 = vdup_n_s16(cospi_16_64);

  q2s32 = vmull_s16(d16s16, d0s16);
  q3s32 = vmull_s16(d17s16, d0s16);
  q13s32 = vmull_s16(d16s16, d0s16);
  q15s32 = vmull_s16(d17s16, d0s16);

  q2s32 = vmlal_s16(q2s32, d24s16, d0s16);
  q3s32 = vmlal_s16(q3s32, d25s16, d0s16);
  q13s32 = vmlsl_s16(q13s32, d24s16, d0s16);
  q15s32 = vmlsl_s16(q15s32, d25s16, d0s16);

  d0s16 = vdup_n_s16(cospi_24_64);
  d1s16 = vdup_n_s16(cospi_8_64);

  d18s16 = vrshrn_n_s32(q2s32, 14);
  d19s16 = vrshrn_n_s32(q3s32, 14);
  d22s16 = vrshrn_n_s32(q13s32, 14);
  d23s16 = vrshrn_n_s32(q15s32, 14);
  *q9s16 = vcombine_s16(d18s16, d19s16);
  *q11s16 = vcombine_s16(d22s16, d23s16);

  q2s32 = vmull_s16(d20s16, d0s16);
  q3s32 = vmull_s16(d21s16, d0s16);
  q8s32 = vmull_s16(d20s16, d1s16);
  q12s32 = vmull_s16(d21s16, d1s16);

  q2s32 = vmlsl_s16(q2s32, d28s16, d1s16);
  q3s32 = vmlsl_s16(q3s32, d29s16, d1s16);
  q8s32 = vmlal_s16(q8s32, d28s16, d0s16);
  q12s32 = vmlal_s16(q12s32, d29s16, d0s16);

  d26s16 = vrshrn_n_s32(q2s32, 14);
  d27s16 = vrshrn_n_s32(q3s32, 14);
  d30s16 = vrshrn_n_s32(q8s32, 14);
  d31s16 = vrshrn_n_s32(q12s32, 14);
  *q13s16 = vcombine_s16(d26s16, d27s16);
  *q15s16 = vcombine_s16(d30s16, d31s16);

  q0s16 = vaddq_s16(*q9s16, *q15s16);
  q1s16 = vaddq_s16(*q11s16, *q13s16);
  q2s16 = vsubq_s16(*q11s16, *q13s16);
  q3s16 = vsubq_s16(*q9s16, *q15s16);

  *q13s16 = vsubq_s16(q4s16, q5s16);
  q4s16 = vaddq_s16(q4s16, q5s16);
  *q14s16 = vsubq_s16(q7s16, q6s16);
  q7s16 = vaddq_s16(q7s16, q6s16);
  d26s16 = vget_low_s16(*q13s16);
  d27s16 = vget_high_s16(*q13s16);
  d28s16 = vget_low_s16(*q14s16);
  d29s16 = vget_high_s16(*q14s16);

  d16s16 = vdup_n_s16(cospi_16_64);

  q9s32 = vmull_s16(d28s16, d16s16);
  q10s32 = vmull_s16(d29s16, d16s16);
  q11s32 = vmull_s16(d28s16, d16s16);
  q12s32 = vmull_s16(d29s16, d16s16);

  q9s32 = vmlsl_s16(q9s32, d26s16, d16s16);
  q10s32 = vmlsl_s16(q10s32, d27s16, d16s16);
  q11s32 = vmlal_s16(q11s32, d26s16, d16s16);
  q12s32 = vmlal_s16(q12s32, d27s16, d16s16);

  d10s16 = vrshrn_n_s32(q9s32, 14);
  d11s16 = vrshrn_n_s32(q10s32, 14);
  d12s16 = vrshrn_n_s32(q11s32, 14);
  d13s16 = vrshrn_n_s32(q12s32, 14);
  q5s16 = vcombine_s16(d10s16, d11s16);
  q6s16 = vcombine_s16(d12s16, d13s16);

  *q8s16 = vaddq_s16(q0s16, q7s16);
  *q9s16 = vaddq_s16(q1s16, q6s16);
  *q10s16 = vaddq_s16(q2s16, q5s16);
  *q11s16 = vaddq_s16(q3s16, q4s16);
  *q12s16 = vsubq_s16(q3s16, q4s16);
  *q13s16 = vsubq_s16(q2s16, q5s16);
  *q14s16 = vsubq_s16(q1s16, q6s16);
  *q15s16 = vsubq_s16(q0s16, q7s16);
}

static INLINE void IADST8X8_1D(int16x8_t *q8s16, int16x8_t *q9s16,
                               int16x8_t *q10s16, int16x8_t *q11s16,
                               int16x8_t *q12s16, int16x8_t *q13s16,
                               int16x8_t *q14s16, int16x8_t *q15s16) {
  int16x4_t d0s16, d1s16, d2s16, d3s16, d4s16, d5s16, d6s16, d7s16;
  int16x4_t d8s16, d9s16, d10s16, d11s16, d12s16, d13s16, d14s16, d15s16;
  int16x4_t d16s16, d17s16, d18s16, d19s16, d20s16, d21s16, d22s16, d23s16;
  int16x4_t d24s16, d25s16, d26s16, d27s16, d28s16, d29s16, d30s16, d31s16;
  int16x8_t q2s16, q4s16, q5s16, q6s16;
  int32x4_t q0s32, q1s32, q2s32, q3s32, q4s32, q5s32, q6s32, q7s32, q8s32;
  int32x4_t q9s32, q10s32, q11s32, q12s32, q13s32, q14s32, q15s32;

  d16s16 = vget_low_s16(*q8s16);
  d17s16 = vget_high_s16(*q8s16);
  d18s16 = vget_low_s16(*q9s16);
  d19s16 = vget_high_s16(*q9s16);
  d20s16 = vget_low_s16(*q10s16);
  d21s16 = vget_high_s16(*q10s16);
  d22s16 = vget_low_s16(*q11s16);
  d23s16 = vget_high_s16(*q11s16);
  d24s16 = vget_low_s16(*q12s16);
  d25s16 = vget_high_s16(*q12s16);
  d26s16 = vget_low_s16(*q13s16);
  d27s16 = vget_high_s16(*q13s16);
  d28s16 = vget_low_s16(*q14s16);
  d29s16 = vget_high_s16(*q14s16);
  d30s16 = vget_low_s16(*q15s16);
  d31s16 = vget_high_s16(*q15s16);

  d14s16 = vdup_n_s16(cospi_2_64);
  d15s16 = vdup_n_s16(cospi_30_64);

  q1s32 = vmull_s16(d30s16, d14s16);
  q2s32 = vmull_s16(d31s16, d14s16);
  q3s32 = vmull_s16(d30s16, d15s16);
  q4s32 = vmull_s16(d31s16, d15s16);

  d30s16 = vdup_n_s16(cospi_18_64);
  d31s16 = vdup_n_s16(cospi_14_64);

  q1s32 = vmlal_s16(q1s32, d16s16, d15s16);
  q2s32 = vmlal_s16(q2s32, d17s16, d15s16);
  q3s32 = vmlsl_s16(q3s32, d16s16, d14s16);
  q4s32 = vmlsl_s16(q4s32, d17s16, d14s16);

  q5s32 = vmull_s16(d22s16, d30s16);
  q6s32 = vmull_s16(d23s16, d30s16);
  q7s32 = vmull_s16(d22s16, d31s16);
  q8s32 = vmull_s16(d23s16, d31s16);

  q5s32 = vmlal_s16(q5s32, d24s16, d31s16);
  q6s32 = vmlal_s16(q6s32, d25s16, d31s16);
  q7s32 = vmlsl_s16(q7s32, d24s16, d30s16);
  q8s32 = vmlsl_s16(q8s32, d25s16, d30s16);

  q11s32 = vaddq_s32(q1s32, q5s32);
  q12s32 = vaddq_s32(q2s32, q6s32);
  q1s32 = vsubq_s32(q1s32, q5s32);
  q2s32 = vsubq_s32(q2s32, q6s32);

  d22s16 = vrshrn_n_s32(q11s32, 14);
  d23s16 = vrshrn_n_s32(q12s32, 14);
  *q11s16 = vcombine_s16(d22s16, d23s16);

  q12s32 = vaddq_s32(q3s32, q7s32);
  q15s32 = vaddq_s32(q4s32, q8s32);
  q3s32 = vsubq_s32(q3s32, q7s32);
  q4s32 = vsubq_s32(q4s32, q8s32);

  d2s16 = vrshrn_n_s32(q1s32, 14);
  d3s16 = vrshrn_n_s32(q2s32, 14);
  d24s16 = vrshrn_n_s32(q12s32, 14);
  d25s16 = vrshrn_n_s32(q15s32, 14);
  d6s16 = vrshrn_n_s32(q3s32, 14);
  d7s16 = vrshrn_n_s32(q4s32, 14);
  *q12s16 = vcombine_s16(d24s16, d25s16);

  d0s16 = vdup_n_s16(cospi_10_64);
  d1s16 = vdup_n_s16(cospi_22_64);
  q4s32 = vmull_s16(d26s16, d0s16);
  q5s32 = vmull_s16(d27s16, d0s16);
  q2s32 = vmull_s16(d26s16, d1s16);
  q6s32 = vmull_s16(d27s16, d1s16);

  d30s16 = vdup_n_s16(cospi_26_64);
  d31s16 = vdup_n_s16(cospi_6_64);

  q4s32 = vmlal_s16(q4s32, d20s16, d1s16);
  q5s32 = vmlal_s16(q5s32, d21s16, d1s16);
  q2s32 = vmlsl_s16(q2s32, d20s16, d0s16);
  q6s32 = vmlsl_s16(q6s32, d21s16, d0s16);

  q0s32 = vmull_s16(d18s16, d30s16);
  q13s32 = vmull_s16(d19s16, d30s16);

  q0s32 = vmlal_s16(q0s32, d28s16, d31s16);
  q13s32 = vmlal_s16(q13s32, d29s16, d31s16);

  q10s32 = vmull_s16(d18s16, d31s16);
  q9s32 = vmull_s16(d19s16, d31s16);

  q10s32 = vmlsl_s16(q10s32, d28s16, d30s16);
  q9s32 = vmlsl_s16(q9s32, d29s16, d30s16);

  q14s32 = vaddq_s32(q2s32, q10s32);
  q15s32 = vaddq_s32(q6s32, q9s32);
  q2s32 = vsubq_s32(q2s32, q10s32);
  q6s32 = vsubq_s32(q6s32, q9s32);

  d28s16 = vrshrn_n_s32(q14s32, 14);
  d29s16 = vrshrn_n_s32(q15s32, 14);
  d4s16 = vrshrn_n_s32(q2s32, 14);
  d5s16 = vrshrn_n_s32(q6s32, 14);
  *q14s16 = vcombine_s16(d28s16, d29s16);

  q9s32 = vaddq_s32(q4s32, q0s32);
  q10s32 = vaddq_s32(q5s32, q13s32);
  q4s32 = vsubq_s32(q4s32, q0s32);
  q5s32 = vsubq_s32(q5s32, q13s32);

  d30s16 = vdup_n_s16(cospi_8_64);
  d31s16 = vdup_n_s16(cospi_24_64);

  d18s16 = vrshrn_n_s32(q9s32, 14);
  d19s16 = vrshrn_n_s32(q10s32, 14);
  d8s16 = vrshrn_n_s32(q4s32, 14);
  d9s16 = vrshrn_n_s32(q5s32, 14);
  *q9s16 = vcombine_s16(d18s16, d19s16);

  q5s32 = vmull_s16(d2s16, d30s16);
  q6s32 = vmull_s16(d3s16, d30s16);
  q7s32 = vmull_s16(d2s16, d31s16);
  q0s32 = vmull_s16(d3s16, d31s16);

  q5s32 = vmlal_s16(q5s32, d6s16, d31s16);
  q6s32 = vmlal_s16(q6s32, d7s16, d31s16);
  q7s32 = vmlsl_s16(q7s32, d6s16, d30s16);
  q0s32 = vmlsl_s16(q0s32, d7s16, d30s16);

  q1s32 = vmull_s16(d4s16, d30s16);
  q3s32 = vmull_s16(d5s16, d30s16);
  q10s32 = vmull_s16(d4s16, d31s16);
  q2s32 = vmull_s16(d5s16, d31s16);

  q1s32 = vmlsl_s16(q1s32, d8s16, d31s16);
  q3s32 = vmlsl_s16(q3s32, d9s16, d31s16);
  q10s32 = vmlal_s16(q10s32, d8s16, d30s16);
  q2s32 = vmlal_s16(q2s32, d9s16, d30s16);

  *q8s16 = vaddq_s16(*q11s16, *q9s16);
  *q11s16 = vsubq_s16(*q11s16, *q9s16);
  q4s16 = vaddq_s16(*q12s16, *q14s16);
  *q12s16 = vsubq_s16(*q12s16, *q14s16);

  q14s32 = vaddq_s32(q5s32, q1s32);
  q15s32 = vaddq_s32(q6s32, q3s32);
  q5s32 = vsubq_s32(q5s32, q1s32);
  q6s32 = vsubq_s32(q6s32, q3s32);

  d18s16 = vrshrn_n_s32(q14s32, 14);
  d19s16 = vrshrn_n_s32(q15s32, 14);
  d10s16 = vrshrn_n_s32(q5s32, 14);
  d11s16 = vrshrn_n_s32(q6s32, 14);
  *q9s16 = vcombine_s16(d18s16, d19s16);

  q1s32 = vaddq_s32(q7s32, q10s32);
  q3s32 = vaddq_s32(q0s32, q2s32);
  q7s32 = vsubq_s32(q7s32, q10s32);
  q0s32 = vsubq_s32(q0s32, q2s32);

  d28s16 = vrshrn_n_s32(q1s32, 14);
  d29s16 = vrshrn_n_s32(q3s32, 14);
  d14s16 = vrshrn_n_s32(q7s32, 14);
  d15s16 = vrshrn_n_s32(q0s32, 14);
  *q14s16 = vcombine_s16(d28s16, d29s16);

  d30s16 = vdup_n_s16(cospi_16_64);

  d22s16 = vget_low_s16(*q11s16);
  d23s16 = vget_high_s16(*q11s16);
  q2s32 = vmull_s16(d22s16, d30s16);
  q3s32 = vmull_s16(d23s16, d30s16);
  q13s32 = vmull_s16(d22s16, d30s16);
  q1s32 = vmull_s16(d23s16, d30s16);

  d24s16 = vget_low_s16(*q12s16);
  d25s16 = vget_high_s16(*q12s16);
  q2s32 = vmlal_s16(q2s32, d24s16, d30s16);
  q3s32 = vmlal_s16(q3s32, d25s16, d30s16);
  q13s32 = vmlsl_s16(q13s32, d24s16, d30s16);
  q1s32 = vmlsl_s16(q1s32, d25s16, d30s16);

  d4s16 = vrshrn_n_s32(q2s32, 14);
  d5s16 = vrshrn_n_s32(q3s32, 14);
  d24s16 = vrshrn_n_s32(q13s32, 14);
  d25s16 = vrshrn_n_s32(q1s32, 14);
  q2s16 = vcombine_s16(d4s16, d5s16);
  *q12s16 = vcombine_s16(d24s16, d25s16);

  q13s32 = vmull_s16(d10s16, d30s16);
  q1s32 = vmull_s16(d11s16, d30s16);
  q11s32 = vmull_s16(d10s16, d30s16);
  q0s32 = vmull_s16(d11s16, d30s16);

  q13s32 = vmlal_s16(q13s32, d14s16, d30s16);
  q1s32 = vmlal_s16(q1s32, d15s16, d30s16);
  q11s32 = vmlsl_s16(q11s32, d14s16, d30s16);
  q0s32 = vmlsl_s16(q0s32, d15s16, d30s16);

  d20s16 = vrshrn_n_s32(q13s32, 14);
  d21s16 = vrshrn_n_s32(q1s32, 14);
  d12s16 = vrshrn_n_s32(q11s32, 14);
  d13s16 = vrshrn_n_s32(q0s32, 14);
  *q10s16 = vcombine_s16(d20s16, d21s16);
  q6s16 = vcombine_s16(d12s16, d13s16);

  q5s16 = vdupq_n_s16(0);

  *q9s16 = vsubq_s16(q5s16, *q9s16);
  *q11s16 = vsubq_s16(q5s16, q2s16);
  *q13s16 = vsubq_s16(q5s16, q6s16);
  *q15s16 = vsubq_s16(q5s16, q4s16);
}

void vp9_iht8x8_64_add_neon(const tran_low_t *input, uint8_t *dest, int stride,
                            int tx_type) {
  int i;
  uint8_t *d1, *d2;
  uint8x8_t d0u8, d1u8, d2u8, d3u8;
  uint64x1_t d0u64, d1u64, d2u64, d3u64;
  int16x8_t q8s16, q9s16, q10s16, q11s16, q12s16, q13s16, q14s16, q15s16;
  uint16x8_t q8u16, q9u16, q10u16, q11u16;

  q8s16 = vld1q_s16(input);
  q9s16 = vld1q_s16(input + 8);
  q10s16 = vld1q_s16(input + 8 * 2);
  q11s16 = vld1q_s16(input + 8 * 3);
  q12s16 = vld1q_s16(input + 8 * 4);
  q13s16 = vld1q_s16(input + 8 * 5);
  q14s16 = vld1q_s16(input + 8 * 6);
  q15s16 = vld1q_s16(input + 8 * 7);

  transpose_s16_8x8(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16, &q14s16,
                    &q15s16);

  switch (tx_type) {
    case 0:  // idct_idct is not supported. Fall back to C
      vp9_iht8x8_64_add_c(input, dest, stride, tx_type);
      return;
    case 1:  // iadst_idct
      // generate IDCT constants
      // GENERATE_IDCT_CONSTANTS

      // first transform rows
      IDCT8x8_1D(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16, &q14s16,
                 &q15s16);

      // transpose the matrix
      transpose_s16_8x8(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16,
                        &q14s16, &q15s16);

      // generate IADST constants
      // GENERATE_IADST_CONSTANTS

      // then transform columns
      IADST8X8_1D(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16, &q14s16,
                  &q15s16);
      break;
    case 2:  // idct_iadst
      // generate IADST constants
      // GENERATE_IADST_CONSTANTS

      // first transform rows
      IADST8X8_1D(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16, &q14s16,
                  &q15s16);

      // transpose the matrix
      transpose_s16_8x8(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16,
                        &q14s16, &q15s16);

      // generate IDCT constants
      // GENERATE_IDCT_CONSTANTS

      // then transform columns
      IDCT8x8_1D(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16, &q14s16,
                 &q15s16);
      break;
    case 3:  // iadst_iadst
      // generate IADST constants
      // GENERATE_IADST_CONSTANTS

      // first transform rows
      IADST8X8_1D(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16, &q14s16,
                  &q15s16);

      // transpose the matrix
      transpose_s16_8x8(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16,
                        &q14s16, &q15s16);

      // then transform columns
      IADST8X8_1D(&q8s16, &q9s16, &q10s16, &q11s16, &q12s16, &q13s16, &q14s16,
                  &q15s16);
      break;
    default:  // iadst_idct
      assert(0);
      break;
  }

  q8s16 = vrshrq_n_s16(q8s16, 5);
  q9s16 = vrshrq_n_s16(q9s16, 5);
  q10s16 = vrshrq_n_s16(q10s16, 5);
  q11s16 = vrshrq_n_s16(q11s16, 5);
  q12s16 = vrshrq_n_s16(q12s16, 5);
  q13s16 = vrshrq_n_s16(q13s16, 5);
  q14s16 = vrshrq_n_s16(q14s16, 5);
  q15s16 = vrshrq_n_s16(q15s16, 5);

  for (d1 = d2 = dest, i = 0; i < 2; i++) {
    if (i != 0) {
      q8s16 = q12s16;
      q9s16 = q13s16;
      q10s16 = q14s16;
      q11s16 = q15s16;
    }

    d0u64 = vld1_u64((uint64_t *)d1);
    d1 += stride;
    d1u64 = vld1_u64((uint64_t *)d1);
    d1 += stride;
    d2u64 = vld1_u64((uint64_t *)d1);
    d1 += stride;
    d3u64 = vld1_u64((uint64_t *)d1);
    d1 += stride;

    q8u16 = vaddw_u8(vreinterpretq_u16_s16(q8s16), vreinterpret_u8_u64(d0u64));
    q9u16 = vaddw_u8(vreinterpretq_u16_s16(q9s16), vreinterpret_u8_u64(d1u64));
    q10u16 =
        vaddw_u8(vreinterpretq_u16_s16(q10s16), vreinterpret_u8_u64(d2u64));
    q11u16 =
        vaddw_u8(vreinterpretq_u16_s16(q11s16), vreinterpret_u8_u64(d3u64));

    d0u8 = vqmovun_s16(vreinterpretq_s16_u16(q8u16));
    d1u8 = vqmovun_s16(vreinterpretq_s16_u16(q9u16));
    d2u8 = vqmovun_s16(vreinterpretq_s16_u16(q10u16));
    d3u8 = vqmovun_s16(vreinterpretq_s16_u16(q11u16));

    vst1_u64((uint64_t *)d2, vreinterpret_u64_u8(d0u8));
    d2 += stride;
    vst1_u64((uint64_t *)d2, vreinterpret_u64_u8(d1u8));
    d2 += stride;
    vst1_u64((uint64_t *)d2, vreinterpret_u64_u8(d2u8));
    d2 += stride;
    vst1_u64((uint64_t *)d2, vreinterpret_u64_u8(d3u8));
    d2 += stride;
  }
}