godot/drivers/webp/dsp/dec_neon.c

// Copyright 2012 Google Inc. All Rights Reserved.
//
// This code is licensed under the same terms as WebM:
//  Software License Agreement:  http://www.webmproject.org/license/software/
//  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
// -----------------------------------------------------------------------------
//
// ARM NEON version of dsp functions and loop filtering.
//
// Authors: Somnath Banerjee (somnath@google.com)
//          Johann Koenig (johannkoenig@google.com)

#include "./dsp.h"

#if defined(WEBP_USE_NEON)

#include "../dec/vp8i.h"

#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

#define QRegs "q0", "q1", "q2", "q3", "q4", "q5", "q6", "q7",                  \
              "q8", "q9", "q10", "q11", "q12", "q13", "q14", "q15"

#define FLIP_SIGN_BIT2(a, b, s)                                                \
  "veor     " #a "," #a "," #s "               \n"                             \
  "veor     " #b "," #b "," #s "               \n"                             \

#define FLIP_SIGN_BIT4(a, b, c, d, s)                                          \
  FLIP_SIGN_BIT2(a, b, s)                                                      \
  FLIP_SIGN_BIT2(c, d, s)                                                      \

#define NEEDS_FILTER(p1, p0, q0, q1, thresh, mask)                             \
  "vabd.u8    q15," #p0 "," #q0 "         \n"  /* abs(p0 - q0) */              \
  "vabd.u8    q14," #p1 "," #q1 "         \n"  /* abs(p1 - q1) */              \
  "vqadd.u8   q15, q15, q15               \n"  /* abs(p0 - q0) * 2 */          \
  "vshr.u8    q14, q14, #1                \n"  /* abs(p1 - q1) / 2 */          \
  "vqadd.u8   q15, q15, q14     \n"  /* abs(p0 - q0) * 2 + abs(p1 - q1) / 2 */ \
  "vdup.8     q14, " #thresh "            \n"                                  \
  "vcge.u8   " #mask ", q14, q15          \n"  /* mask <= thresh */

#define GET_BASE_DELTA(p1, p0, q0, q1, o)                                      \
  "vqsub.s8   q15," #q0 "," #p0 "         \n"  /* (q0 - p0) */                 \
  "vqsub.s8  " #o "," #p1 "," #q1 "       \n"  /* (p1 - q1) */                 \
  "vqadd.s8  " #o "," #o ", q15           \n"  /* (p1 - q1) + 1 * (p0 - q0) */ \
  "vqadd.s8  " #o "," #o ", q15           \n"  /* (p1 - q1) + 2 * (p0 - q0) */ \
  "vqadd.s8  " #o "," #o ", q15           \n"  /* (p1 - q1) + 3 * (p0 - q0) */

#define DO_SIMPLE_FILTER(p0, q0, fl)                                           \
  "vmov.i8    q15, #0x03                  \n"                                  \
  "vqadd.s8   q15, q15, " #fl "           \n"  /* filter1 = filter + 3 */      \
  "vshr.s8    q15, q15, #3                \n"  /* filter1 >> 3 */              \
  "vqadd.s8  " #p0 "," #p0 ", q15         \n"  /* p0 += filter1 */             \
                                                                               \
  "vmov.i8    q15, #0x04                  \n"                                  \
  "vqadd.s8   q15, q15, " #fl "           \n"  /* filter1 = filter + 4 */      \
  "vshr.s8    q15, q15, #3                \n"  /* filter2 >> 3 */              \
  "vqsub.s8  " #q0 "," #q0 ", q15         \n"  /* q0 -= filter2 */

// Applies filter on 2 pixels (p0 and q0)
#define DO_FILTER2(p1, p0, q0, q1, thresh)                                     \
  NEEDS_FILTER(p1, p0, q0, q1, thresh, q9)     /* filter mask in q9 */         \
  "vmov.i8    q10, #0x80                  \n"  /* sign bit */                  \
  FLIP_SIGN_BIT4(p1, p0, q0, q1, q10)          /* convert to signed value */   \
  GET_BASE_DELTA(p1, p0, q0, q1, q11)          /* get filter level  */         \
  "vand       q9, q9, q11                 \n"  /* apply filter mask */         \
  DO_SIMPLE_FILTER(p0, q0, q9)                 /* apply filter */              \
  FLIP_SIGN_BIT2(p0, q0, q10)

// Load/Store vertical edge
#define LOAD8x4(c1, c2, c3, c4, b1, b2, stride)                                \
  "vld4.8   {" #c1"[0], " #c2"[0], " #c3"[0], " #c4"[0]}," #b1 "," #stride"\n" \
  "vld4.8   {" #c1"[1], " #c2"[1], " #c3"[1], " #c4"[1]}," #b2 "," #stride"\n" \
  "vld4.8   {" #c1"[2], " #c2"[2], " #c3"[2], " #c4"[2]}," #b1 "," #stride"\n" \
  "vld4.8   {" #c1"[3], " #c2"[3], " #c3"[3], " #c4"[3]}," #b2 "," #stride"\n" \
  "vld4.8   {" #c1"[4], " #c2"[4], " #c3"[4], " #c4"[4]}," #b1 "," #stride"\n" \
  "vld4.8   {" #c1"[5], " #c2"[5], " #c3"[5], " #c4"[5]}," #b2 "," #stride"\n" \
  "vld4.8   {" #c1"[6], " #c2"[6], " #c3"[6], " #c4"[6]}," #b1 "," #stride"\n" \
  "vld4.8   {" #c1"[7], " #c2"[7], " #c3"[7], " #c4"[7]}," #b2 "," #stride"\n"

#define STORE8x2(c1, c2, p,stride)                                             \
  "vst2.8   {" #c1"[0], " #c2"[0]}," #p "," #stride " \n"                      \
  "vst2.8   {" #c1"[1], " #c2"[1]}," #p "," #stride " \n"                      \
  "vst2.8   {" #c1"[2], " #c2"[2]}," #p "," #stride " \n"                      \
  "vst2.8   {" #c1"[3], " #c2"[3]}," #p "," #stride " \n"                      \
  "vst2.8   {" #c1"[4], " #c2"[4]}," #p "," #stride " \n"                      \
  "vst2.8   {" #c1"[5], " #c2"[5]}," #p "," #stride " \n"                      \
  "vst2.8   {" #c1"[6], " #c2"[6]}," #p "," #stride " \n"                      \
  "vst2.8   {" #c1"[7], " #c2"[7]}," #p "," #stride " \n"

//-----------------------------------------------------------------------------
// Simple In-loop filtering (Paragraph 15.2)

static void SimpleVFilter16NEON(uint8_t* p, int stride, int thresh) {
  __asm__ volatile (
    "sub        %[p], %[p], %[stride], lsl #1  \n"  // p -= 2 * stride

    "vld1.u8    {q1}, [%[p]], %[stride]        \n"  // p1
    "vld1.u8    {q2}, [%[p]], %[stride]        \n"  // p0
    "vld1.u8    {q3}, [%[p]], %[stride]        \n"  // q0
    "vld1.u8    {q4}, [%[p]]                   \n"  // q1

    DO_FILTER2(q1, q2, q3, q4, %[thresh])

    "sub        %[p], %[p], %[stride], lsl #1  \n"  // p -= 2 * stride

    "vst1.u8    {q2}, [%[p]], %[stride]        \n"  // store op0
    "vst1.u8    {q3}, [%[p]]                   \n"  // store oq0
    : [p] "+r"(p)
    : [stride] "r"(stride), [thresh] "r"(thresh)
    : "memory", QRegs
  );
}

static void SimpleHFilter16NEON(uint8_t* p, int stride, int thresh) {
  __asm__ volatile (
    "sub        r4, %[p], #2                   \n"  // base1 = p - 2
    "lsl        r6, %[stride], #1              \n"  // r6 = 2 * stride
    "add        r5, r4, %[stride]              \n"  // base2 = base1 + stride

    LOAD8x4(d2, d3, d4, d5, [r4], [r5], r6)
    LOAD8x4(d6, d7, d8, d9, [r4], [r5], r6)
    "vswp       d3, d6                         \n"  // p1:q1 p0:q3
    "vswp       d5, d8                         \n"  // q0:q2 q1:q4
    "vswp       q2, q3                         \n"  // p1:q1 p0:q2 q0:q3 q1:q4

    DO_FILTER2(q1, q2, q3, q4, %[thresh])

    "sub        %[p], %[p], #1                 \n"  // p - 1

    "vswp        d5, d6                        \n"
    STORE8x2(d4, d5, [%[p]], %[stride])
    STORE8x2(d6, d7, [%[p]], %[stride])

    : [p] "+r"(p)
    : [stride] "r"(stride), [thresh] "r"(thresh)
    : "memory", "r4", "r5", "r6", QRegs
  );
}

static void SimpleVFilter16iNEON(uint8_t* p, int stride, int thresh) {
  int k;
  for (k = 3; k > 0; --k) {
    p += 4 * stride;
    SimpleVFilter16NEON(p, stride, thresh);
  }
}

static void SimpleHFilter16iNEON(uint8_t* p, int stride, int thresh) {
  int k;
  for (k = 3; k > 0; --k) {
    p += 4;
    SimpleHFilter16NEON(p, stride, thresh);
  }
}

static void TransformOneNEON(const int16_t *in, uint8_t *dst) {
  const int kBPS = BPS;
  const int16_t constants[] = {20091, 17734, 0, 0};
  /* kC1, kC2. Padded because vld1.16 loads 8 bytes
   * Technically these are unsigned but vqdmulh is only available in signed.
   * vqdmulh returns high half (effectively >> 16) but also doubles the value,
   * changing the >> 16 to >> 15 and requiring an additional >> 1.
   * We use this to our advantage with kC2. The canonical value is 35468.
   * However, the high bit is set so treating it as signed will give incorrect
   * results. We avoid this by down shifting by 1 here to clear the highest bit.
   * Combined with the doubling effect of vqdmulh we get >> 16.
   * This can not be applied to kC1 because the lowest bit is set. Down shifting
   * the constant would reduce precision.
   */

  /* libwebp uses a trick to avoid some extra addition that libvpx does.
   * Instead of:
   * temp2 = ip[12] + ((ip[12] * cospi8sqrt2minus1) >> 16);
   * libwebp adds 1 << 16 to cospi8sqrt2minus1 (kC1). However, this causes the
   * same issue with kC1 and vqdmulh that we work around by down shifting kC2
   */

  /* Adapted from libvpx: vp8/common/arm/neon/shortidct4x4llm_neon.asm */
  __asm__ volatile (
    "vld1.16         {q1, q2}, [%[in]]           \n"
    "vld1.16         {d0}, [%[constants]]        \n"

    /* d2: in[0]
     * d3: in[8]
     * d4: in[4]
     * d5: in[12]
     */
    "vswp            d3, d4                      \n"

    /* q8 = {in[4], in[12]} * kC1 * 2 >> 16
     * q9 = {in[4], in[12]} * kC2 >> 16
     */
    "vqdmulh.s16     q8, q2, d0[0]               \n"
    "vqdmulh.s16     q9, q2, d0[1]               \n"

    /* d22 = a = in[0] + in[8]
     * d23 = b = in[0] - in[8]
     */
    "vqadd.s16       d22, d2, d3                 \n"
    "vqsub.s16       d23, d2, d3                 \n"

    /* The multiplication should be x * kC1 >> 16
     * However, with vqdmulh we get x * kC1 * 2 >> 16
     * (multiply, double, return high half)
     * We avoided this in kC2 by pre-shifting the constant.
     * q8 = in[4]/[12] * kC1 >> 16
     */
    "vshr.s16        q8, q8, #1                  \n"

    /* Add {in[4], in[12]} back after the multiplication. This is handled by
     * adding 1 << 16 to kC1 in the libwebp C code.
     */
    "vqadd.s16       q8, q2, q8                  \n"

    /* d20 = c = in[4]*kC2 - in[12]*kC1
     * d21 = d = in[4]*kC1 + in[12]*kC2
     */
    "vqsub.s16       d20, d18, d17               \n"
    "vqadd.s16       d21, d19, d16               \n"

    /* d2 = tmp[0] = a + d
     * d3 = tmp[1] = b + c
     * d4 = tmp[2] = b - c
     * d5 = tmp[3] = a - d
     */
    "vqadd.s16       d2, d22, d21                \n"
    "vqadd.s16       d3, d23, d20                \n"
    "vqsub.s16       d4, d23, d20                \n"
    "vqsub.s16       d5, d22, d21                \n"

    "vzip.16         q1, q2                      \n"
    "vzip.16         q1, q2                      \n"

    "vswp            d3, d4                      \n"

    /* q8 = {tmp[4], tmp[12]} * kC1 * 2 >> 16
     * q9 = {tmp[4], tmp[12]} * kC2 >> 16
     */
    "vqdmulh.s16     q8, q2, d0[0]               \n"
    "vqdmulh.s16     q9, q2, d0[1]               \n"

    /* d22 = a = tmp[0] + tmp[8]
     * d23 = b = tmp[0] - tmp[8]
     */
    "vqadd.s16       d22, d2, d3                 \n"
    "vqsub.s16       d23, d2, d3                 \n"

    /* See long winded explanations prior */
    "vshr.s16        q8, q8, #1                  \n"
    "vqadd.s16       q8, q2, q8                  \n"

    /* d20 = c = in[4]*kC2 - in[12]*kC1
     * d21 = d = in[4]*kC1 + in[12]*kC2
     */
    "vqsub.s16       d20, d18, d17               \n"
    "vqadd.s16       d21, d19, d16               \n"

    /* d2 = tmp[0] = a + d
     * d3 = tmp[1] = b + c
     * d4 = tmp[2] = b - c
     * d5 = tmp[3] = a - d
     */
    "vqadd.s16       d2, d22, d21                \n"
    "vqadd.s16       d3, d23, d20                \n"
    "vqsub.s16       d4, d23, d20                \n"
    "vqsub.s16       d5, d22, d21                \n"

    "vld1.32         d6[0], [%[dst]], %[kBPS]    \n"
    "vld1.32         d6[1], [%[dst]], %[kBPS]    \n"
    "vld1.32         d7[0], [%[dst]], %[kBPS]    \n"
    "vld1.32         d7[1], [%[dst]], %[kBPS]    \n"

    "sub         %[dst], %[dst], %[kBPS], lsl #2 \n"

    /* (val) + 4 >> 3 */
    "vrshr.s16       d2, d2, #3                  \n"
    "vrshr.s16       d3, d3, #3                  \n"
    "vrshr.s16       d4, d4, #3                  \n"
    "vrshr.s16       d5, d5, #3                  \n"

    "vzip.16         q1, q2                      \n"
    "vzip.16         q1, q2                      \n"

    /* Must accumulate before saturating */
    "vmovl.u8        q8, d6                      \n"
    "vmovl.u8        q9, d7                      \n"

    "vqadd.s16       q1, q1, q8                  \n"
    "vqadd.s16       q2, q2, q9                  \n"

    "vqmovun.s16     d0, q1                      \n"
    "vqmovun.s16     d1, q2                      \n"

    "vst1.32         d0[0], [%[dst]], %[kBPS]    \n"
    "vst1.32         d0[1], [%[dst]], %[kBPS]    \n"
    "vst1.32         d1[0], [%[dst]], %[kBPS]    \n"
    "vst1.32         d1[1], [%[dst]]             \n"

    : [in] "+r"(in), [dst] "+r"(dst)  /* modified registers */
    : [kBPS] "r"(kBPS), [constants] "r"(constants)  /* constants */
    : "memory", "q0", "q1", "q2", "q8", "q9", "q10", "q11"  /* clobbered */
  );
}

static void TransformTwoNEON(const int16_t* in, uint8_t* dst, int do_two) {
  TransformOneNEON(in, dst);
  if (do_two) {
    TransformOneNEON(in + 16, dst + 4);
  }
}

extern void VP8DspInitNEON(void);

void VP8DspInitNEON(void) {
  VP8Transform = TransformTwoNEON;

  VP8SimpleVFilter16 = SimpleVFilter16NEON;
  VP8SimpleHFilter16 = SimpleHFilter16NEON;
  VP8SimpleVFilter16i = SimpleVFilter16iNEON;
  VP8SimpleHFilter16i = SimpleHFilter16iNEON;
}

#if defined(__cplusplus) || defined(c_plusplus)
}    // extern "C"
#endif

#endif   // WEBP_USE_NEON