libwebp/sharpyuv/sharpyuv_neon.c

// Copyright 2022 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING 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.
// -----------------------------------------------------------------------------
//
// Speed-critical functions for Sharp YUV.
//
// Author: Skal (pascal.massimino@gmail.com)

#include "sharpyuv/sharpyuv_dsp.h"

#if defined(WEBP_USE_NEON)
#include <assert.h>
#include <stdlib.h>
#include <arm_neon.h>
#endif

extern void InitSharpYUVNEON(void);

#if defined(WEBP_USE_NEON)

#define MAX_Y ((1 << 10) - 1)    // 10b precision over 16b-arithmetic
static uint16_t clip_y_NEON(int v) {
  return (v < 0) ? 0 : (v > MAX_Y) ? MAX_Y : (uint16_t)v;
}

static uint64_t SharpYUVUpdateY_NEON(const uint16_t* ref, const uint16_t* src,
                                     uint16_t* dst, int len) {
  int i;
  const int16x8_t zero = vdupq_n_s16(0);
  const int16x8_t max = vdupq_n_s16(MAX_Y);
  uint64x2_t sum = vdupq_n_u64(0);
  uint64_t diff;

  for (i = 0; i + 8 <= len; i += 8) {
    const int16x8_t A = vreinterpretq_s16_u16(vld1q_u16(ref + i));
    const int16x8_t B = vreinterpretq_s16_u16(vld1q_u16(src + i));
    const int16x8_t C = vreinterpretq_s16_u16(vld1q_u16(dst + i));
    const int16x8_t D = vsubq_s16(A, B);       // diff_y
    const int16x8_t F = vaddq_s16(C, D);       // new_y
    const uint16x8_t H =
        vreinterpretq_u16_s16(vmaxq_s16(vminq_s16(F, max), zero));
    const int16x8_t I = vabsq_s16(D);          // abs(diff_y)
    vst1q_u16(dst + i, H);
    sum = vpadalq_u32(sum, vpaddlq_u16(vreinterpretq_u16_s16(I)));
  }
  diff = vgetq_lane_u64(sum, 0) + vgetq_lane_u64(sum, 1);
  for (; i < len; ++i) {
    const int diff_y = ref[i] - src[i];
    const int new_y = (int)(dst[i]) + diff_y;
    dst[i] = clip_y_NEON(new_y);
    diff += (uint64_t)(abs(diff_y));
  }
  return diff;
}

static void SharpYUVUpdateRGB_NEON(const int16_t* ref, const int16_t* src,
                                   int16_t* dst, int len) {
  int i;
  for (i = 0; i + 8 <= len; i += 8) {
    const int16x8_t A = vld1q_s16(ref + i);
    const int16x8_t B = vld1q_s16(src + i);
    const int16x8_t C = vld1q_s16(dst + i);
    const int16x8_t D = vsubq_s16(A, B);   // diff_uv
    const int16x8_t E = vaddq_s16(C, D);   // new_uv
    vst1q_s16(dst + i, E);
  }
  for (; i < len; ++i) {
    const int diff_uv = ref[i] - src[i];
    dst[i] += diff_uv;
  }
}

static void SharpYUVFilterRow_NEON(const int16_t* A, const int16_t* B, int len,
                                   const uint16_t* best_y, uint16_t* out) {
  int i;
  const int16x8_t max = vdupq_n_s16(MAX_Y);
  const int16x8_t zero = vdupq_n_s16(0);
  for (i = 0; i + 8 <= len; i += 8) {
    const int16x8_t a0 = vld1q_s16(A + i + 0);
    const int16x8_t a1 = vld1q_s16(A + i + 1);
    const int16x8_t b0 = vld1q_s16(B + i + 0);
    const int16x8_t b1 = vld1q_s16(B + i + 1);
    const int16x8_t a0b1 = vaddq_s16(a0, b1);
    const int16x8_t a1b0 = vaddq_s16(a1, b0);
    const int16x8_t a0a1b0b1 = vaddq_s16(a0b1, a1b0);  // A0+A1+B0+B1
    const int16x8_t a0b1_2 = vaddq_s16(a0b1, a0b1);    // 2*(A0+B1)
    const int16x8_t a1b0_2 = vaddq_s16(a1b0, a1b0);    // 2*(A1+B0)
    const int16x8_t c0 = vshrq_n_s16(vaddq_s16(a0b1_2, a0a1b0b1), 3);
    const int16x8_t c1 = vshrq_n_s16(vaddq_s16(a1b0_2, a0a1b0b1), 3);
    const int16x8_t d0 = vaddq_s16(c1, a0);
    const int16x8_t d1 = vaddq_s16(c0, a1);
    const int16x8_t e0 = vrshrq_n_s16(d0, 1);
    const int16x8_t e1 = vrshrq_n_s16(d1, 1);
    const int16x8x2_t f = vzipq_s16(e0, e1);
    const int16x8_t g0 = vreinterpretq_s16_u16(vld1q_u16(best_y + 2 * i + 0));
    const int16x8_t g1 = vreinterpretq_s16_u16(vld1q_u16(best_y + 2 * i + 8));
    const int16x8_t h0 = vaddq_s16(g0, f.val[0]);
    const int16x8_t h1 = vaddq_s16(g1, f.val[1]);
    const int16x8_t i0 = vmaxq_s16(vminq_s16(h0, max), zero);
    const int16x8_t i1 = vmaxq_s16(vminq_s16(h1, max), zero);
    vst1q_u16(out + 2 * i + 0, vreinterpretq_u16_s16(i0));
    vst1q_u16(out + 2 * i + 8, vreinterpretq_u16_s16(i1));
  }
  for (; i < len; ++i) {
    const int a0b1 = A[i + 0] + B[i + 1];
    const int a1b0 = A[i + 1] + B[i + 0];
    const int a0a1b0b1 = a0b1 + a1b0 + 8;
    const int v0 = (8 * A[i + 0] + 2 * a1b0 + a0a1b0b1) >> 4;
    const int v1 = (8 * A[i + 1] + 2 * a0b1 + a0a1b0b1) >> 4;
    out[2 * i + 0] = clip_y_NEON(best_y[2 * i + 0] + v0);
    out[2 * i + 1] = clip_y_NEON(best_y[2 * i + 1] + v1);
  }
}
#undef MAX_Y

//------------------------------------------------------------------------------

WEBP_TSAN_IGNORE_FUNCTION void InitSharpYUVNEON(void) {
  SharpYUVUpdateY = SharpYUVUpdateY_NEON;
  SharpYUVUpdateRGB = SharpYUVUpdateRGB_NEON;
  SharpYUVFilterRow = SharpYUVFilterRow_NEON;
}

#else  // !WEBP_USE_NEON

void InitSharpYUVNEON(void) {}

#endif  // WEBP_USE_NEON