/*

 * Copyright © 2020, VideoLAN and dav1d authors

 * Copyright © 2020, Two Orioles, LLC

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *

 * 1. Redistributions of source code must retain the above copyright notice, this

 *    list of conditions and the following disclaimer.

 *

 * 2. Redistributions in binary form must reproduce the above copyright notice,

 *    this list of conditions and the following disclaimer in the documentation

 *    and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR

 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#include "config.h"

#include <limits.h>

#include <stdlib.h>

#include "dav1d/common.h"

#include "common/intops.h"

#include "src/env.h"

#include "src/mem.h"

#include "src/refmvs.h"

static void add_spatial_candidate(refmvs_candidate *const mvstack, int *const cnt,

                                  const int weight, const refmvs_block *const b,

                                  const union refmvs_refpair ref, const mv gmv[2],

                                  int *const have_newmv_match,

                                  int *const have_refmv_match)

{

    if (b->mv.mv[0].n == INVALID_MV) return; // intra block, no intrabc

    if (ref.ref[1] == -1) {

        for (int n = 0; n < 2; n++) {

            if (b->ref.ref[n] == ref.ref[0]) {

                const mv cand_mv = ((b->mf & 1) && gmv[0].n != INVALID_MV) ?

                                   gmv[0] : b->mv.mv[n];

                *have_refmv_match = 1;

                *have_newmv_match |= b->mf >> 1;

                const int last = *cnt;

                for (int m = 0; m < last; m++)

                    if (mvstack[m].mv.mv[0].n == cand_mv.n) {

                        mvstack[m].weight += weight;

                        return;

                    }

                if (last < 8) {

                    mvstack[last].mv.mv[0] = cand_mv;

                    mvstack[last].weight = weight;

                    *cnt = last + 1;

                }

                return;

            }

        }

    } else if (b->ref.pair == ref.pair) {

        const refmvs_mvpair cand_mv = { .mv = {

            [0] = ((b->mf & 1) && gmv[0].n != INVALID_MV) ? gmv[0] : b->mv.mv[0],

            [1] = ((b->mf & 1) && gmv[1].n != INVALID_MV) ? gmv[1] : b->mv.mv[1],

        }};

        *have_refmv_match = 1;

        *have_newmv_match |= b->mf >> 1;

        const int last = *cnt;

        for (int n = 0; n < last; n++)

            if (mvstack[n].mv.n == cand_mv.n) {

                mvstack[n].weight += weight;

                return;

            }

        if (last < 8) {

            mvstack[last].mv = cand_mv;

            mvstack[last].weight = weight;

            *cnt = last + 1;

        }

    }

}

static int scan_row(refmvs_candidate *const mvstack, int *const cnt,

                    const union refmvs_refpair ref, const mv gmv[2],

                    const refmvs_block *b, const int bw4, const int w4,

                    const int max_rows, const int step,

                    int *const have_newmv_match, int *const have_refmv_match)

{

    const refmvs_block *cand_b = b;

    const enum BlockSize first_cand_bs = cand_b->bs;

    const uint8_t *const first_cand_b_dim = dav1d_block_dimensions[first_cand_bs];

    int cand_bw4 = first_cand_b_dim[0];

    int len = imax(step, imin(bw4, cand_bw4));

    if (bw4 <= cand_bw4) {

        // FIXME weight can be higher for odd blocks (bx4 & 1), but then the

        // position of the first block has to be odd already, i.e. not just

        // for row_offset=-3/-5

        // FIXME why can this not be cand_bw4?

        const int weight = bw4 == 1 ? 2 :

                           imax(2, imin(2 * max_rows, first_cand_b_dim[1]));

        add_spatial_candidate(mvstack, cnt, len * weight, cand_b, ref, gmv,

                              have_newmv_match, have_refmv_match);

        return weight >> 1;

    }

    for (int x = 0;;) {

        // FIXME if we overhang above, we could fill a bitmask so we don't have

        // to repeat the add_spatial_candidate() for the next row, but just increase

        // the weight here

        add_spatial_candidate(mvstack, cnt, len * 2, cand_b, ref, gmv,

                              have_newmv_match, have_refmv_match);

        x += len;

        if (x >= w4) return 1;

        cand_b = &b[x];

        cand_bw4 = dav1d_block_dimensions[cand_b->bs][0];

        assert(cand_bw4 < bw4);

        len = imax(step, cand_bw4);

    }

}

static int scan_col(refmvs_candidate *const mvstack, int *const cnt,

                    const union refmvs_refpair ref, const mv gmv[2],

                    /*const*/ refmvs_block *const *b, const int bh4, const int h4,

                    const int bx4, const int max_cols, const int step,

                    int *const have_newmv_match, int *const have_refmv_match)

{

    const refmvs_block *cand_b = &b[0][bx4];

    const enum BlockSize first_cand_bs = cand_b->bs;

    const uint8_t *const first_cand_b_dim = dav1d_block_dimensions[first_cand_bs];

    int cand_bh4 = first_cand_b_dim[1];

    int len = imax(step, imin(bh4, cand_bh4));

    if (bh4 <= cand_bh4) {

        // FIXME weight can be higher for odd blocks (by4 & 1), but then the

        // position of the first block has to be odd already, i.e. not just

        // for col_offset=-3/-5

        // FIXME why can this not be cand_bh4?

        const int weight = bh4 == 1 ? 2 :

                           imax(2, imin(2 * max_cols, first_cand_b_dim[0]));

        add_spatial_candidate(mvstack, cnt, len * weight, cand_b, ref, gmv,

                            have_newmv_match, have_refmv_match);

        return weight >> 1;

    }

    for (int y = 0;;) {

        // FIXME if we overhang above, we could fill a bitmask so we don't have

        // to repeat the add_spatial_candidate() for the next row, but just increase

        // the weight here

        add_spatial_candidate(mvstack, cnt, len * 2, cand_b, ref, gmv,

                              have_newmv_match, have_refmv_match);

        y += len;

        if (y >= h4) return 1;

        cand_b = &b[y][bx4];

        cand_bh4 = dav1d_block_dimensions[cand_b->bs][1];

        assert(cand_bh4 < bh4);

        len = imax(step, cand_bh4);

    }

}

static inline union mv mv_projection(const union mv mv, const int num, const int den) {

    static const uint16_t div_mult[32] = {

           0, 16384, 8192, 5461, 4096, 3276, 2730, 2340,

        2048,  1820, 1638, 1489, 1365, 1260, 1170, 1092,

        1024,   963,  910,  862,  819,  780,  744,  712,

         682,   655,  630,  606,  585,  564,  546,  528

    };

    assert(den > 0 && den < 32);

    assert(num > -32 && num < 32);

    const int frac = num * div_mult[den];

    const int y = mv.y * frac, x = mv.x * frac;

    // Round and clip according to AV1 spec section 7.9.3

    return (union mv) { // 0x3fff == (1 << 14) - 1

        .y = iclip((y + 8192 + (y >> 31)) >> 14, -0x3fff, 0x3fff),

        .x = iclip((x + 8192 + (x >> 31)) >> 14, -0x3fff, 0x3fff)

    };

}

static void add_temporal_candidate(const refmvs_frame *const rf,

                                   refmvs_candidate *const mvstack, int *const cnt,

                                   const refmvs_temporal_block *const rb,

                                   const union refmvs_refpair ref, int *const globalmv_ctx,

                                   const union mv gmv[])

{

    if (rb->mv.n == INVALID_MV) return;

    union mv mv = mv_projection(rb->mv, rf->pocdiff[ref.ref[0] - 1], rb->ref);

    fix_mv_precision(rf->frm_hdr, &mv);

    const int last = *cnt;

    if (ref.ref[1] == -1) {

        if (globalmv_ctx)

            *globalmv_ctx = (abs(mv.x - gmv[0].x) | abs(mv.y - gmv[0].y)) >= 16;

        for (int n = 0; n < last; n++)

            if (mvstack[n].mv.mv[0].n == mv.n) {

                mvstack[n].weight += 2;

                return;

            }

        if (last < 8) {

            mvstack[last].mv.mv[0] = mv;

            mvstack[last].weight = 2;

            *cnt = last + 1;

        }

    } else {

        refmvs_mvpair mvp = { .mv = {

            [0] = mv,

            [1] = mv_projection(rb->mv, rf->pocdiff[ref.ref[1] - 1], rb->ref),

        }};

        fix_mv_precision(rf->frm_hdr, &mvp.mv[1]);

        for (int n = 0; n < last; n++)

            if (mvstack[n].mv.n == mvp.n) {

                mvstack[n].weight += 2;

                return;

            }

        if (last < 8) {

            mvstack[last].mv = mvp;

            mvstack[last].weight = 2;

            *cnt = last + 1;

        }

    }

}

static void add_compound_extended_candidate(refmvs_candidate *const same,

                                            int *const same_count,

                                            const refmvs_block *const cand_b,

                                            const int sign0, const int sign1,

                                            const union refmvs_refpair ref,

                                            const uint8_t *const sign_bias)

{

    refmvs_candidate *const diff = &same[2];

    int *const diff_count = &same_count[2];

    for (int n = 0; n < 2; n++) {

        const int cand_ref = cand_b->ref.ref[n];

        if (cand_ref <= 0) break;

        mv cand_mv = cand_b->mv.mv[n];

        if (cand_ref == ref.ref[0]) {

            if (same_count[0] < 2)

                same[same_count[0]++].mv.mv[0] = cand_mv;

            if (diff_count[1] < 2) {

                if (sign1 ^ sign_bias[cand_ref - 1]) {

                    cand_mv.y = -cand_mv.y;

                    cand_mv.x = -cand_mv.x;

                }

                diff[diff_count[1]++].mv.mv[1] = cand_mv;

            }

        } else if (cand_ref == ref.ref[1]) {

            if (same_count[1] < 2)

                same[same_count[1]++].mv.mv[1] = cand_mv;

            if (diff_count[0] < 2) {

                if (sign0 ^ sign_bias[cand_ref - 1]) {

                    cand_mv.y = -cand_mv.y;

                    cand_mv.x = -cand_mv.x;

                }

                diff[diff_count[0]++].mv.mv[0] = cand_mv;

            }

        } else {

            mv i_cand_mv = (union mv) {

                .x = -cand_mv.x,

                .y = -cand_mv.y

            };

            if (diff_count[0] < 2) {

                diff[diff_count[0]++].mv.mv[0] =

                    sign0 ^ sign_bias[cand_ref - 1] ?

                    i_cand_mv : cand_mv;

            }

            if (diff_count[1] < 2) {

                diff[diff_count[1]++].mv.mv[1] =

                    sign1 ^ sign_bias[cand_ref - 1] ?

                    i_cand_mv : cand_mv;

            }

        }

    }

}

static void add_single_extended_candidate(refmvs_candidate mvstack[8], int *const cnt,

                                          const refmvs_block *const cand_b,

                                          const int sign, const uint8_t *const sign_bias)

{

    for (int n = 0; n < 2; n++) {

        const int cand_ref = cand_b->ref.ref[n];

        if (cand_ref <= 0) break;

        // we need to continue even if cand_ref == ref.ref[0], since

        // the candidate could have been added as a globalmv variant,

        // which changes the value

        // FIXME if scan_{row,col}() returned a mask for the nearest

        // edge, we could skip the appropriate ones here

        mv cand_mv = cand_b->mv.mv[n];

        if (sign ^ sign_bias[cand_ref - 1]) {

            cand_mv.y = -cand_mv.y;

            cand_mv.x = -cand_mv.x;

        }

        int m;

        const int last = *cnt;

        for (m = 0; m < last; m++)

            if (cand_mv.n == mvstack[m].mv.mv[0].n)

                break;

        if (m == last) {

            mvstack[m].mv.mv[0] = cand_mv;

            mvstack[m].weight = 2; // "minimal"

            *cnt = last + 1;

        }

    }

}

/*

 * refmvs_frame allocates memory for one sbrow (32 blocks high, whole frame

 * wide) of 4x4-resolution refmvs_block entries for spatial MV referencing.

 * mvrefs_tile[] keeps a list of 35 (32 + 3 above) pointers into this memory,

 * and each sbrow, the bottom entries (y=27/29/31) are exchanged with the top

 * (-5/-3/-1) pointers by calling dav1d_refmvs_tile_sbrow_init() at the start

 * of each tile/sbrow.

 *

 * For temporal MV referencing, we call dav1d_refmvs_save_tmvs() at the end of

 * each tile/sbrow (when tile column threading is enabled), or at the start of

 * each interleaved sbrow (i.e. once for all tile columns together, when tile

 * column threading is disabled). This will copy the 4x4-resolution spatial MVs

 * into 8x8-resolution refmvs_temporal_block structures. Then, for subsequent

 * frames, at the start of each tile/sbrow (when tile column threading is

 * enabled) or at the start of each interleaved sbrow (when tile column

 * threading is disabled), we call load_tmvs(), which will project the MVs to

 * their respective position in the current frame.

 */

void dav1d_refmvs_find(const refmvs_tile *const rt,

                       refmvs_candidate mvstack[8], int *const cnt,

                       int *const ctx,

                       const union refmvs_refpair ref, const enum BlockSize bs,

                       const enum EdgeFlags edge_flags,

                       const int by4, const int bx4)

{

    const refmvs_frame *const rf = rt->rf;

    const uint8_t *const b_dim = dav1d_block_dimensions[bs];

    const int bw4 = b_dim[0], w4 = imin(imin(bw4, 16), rt->tile_col.end - bx4);

    const int bh4 = b_dim[1], h4 = imin(imin(bh4, 16), rt->tile_row.end - by4);

    mv gmv[2], tgmv[2];

    *cnt = 0;

    assert(ref.ref[0] >=  0 && ref.ref[0] <= 8 &&

           ref.ref[1] >= -1 && ref.ref[1] <= 8);

    if (ref.ref[0] > 0) {

        tgmv[0] = get_gmv_2d(&rf->frm_hdr->gmv[ref.ref[0] - 1],

                             bx4, by4, bw4, bh4, rf->frm_hdr);

        gmv[0] = rf->frm_hdr->gmv[ref.ref[0] - 1].type > DAV1D_WM_TYPE_TRANSLATION ?

                 tgmv[0] : (mv) { .n = INVALID_MV };

    } else {

        tgmv[0] = (mv) { .n = 0 };

        gmv[0] = (mv) { .n = INVALID_MV };

    }

    if (ref.ref[1] > 0) {

        tgmv[1] = get_gmv_2d(&rf->frm_hdr->gmv[ref.ref[1] - 1],

                             bx4, by4, bw4, bh4, rf->frm_hdr);

        gmv[1] = rf->frm_hdr->gmv[ref.ref[1] - 1].type > DAV1D_WM_TYPE_TRANSLATION ?

                 tgmv[1] : (mv) { .n = INVALID_MV };

    }

    // top

    int have_newmv = 0, have_col_mvs = 0, have_row_mvs = 0;

    unsigned max_rows = 0, n_rows = ~0;

    const refmvs_block *b_top;

    if (by4 > rt->tile_row.start) {

        max_rows = imin((by4 - rt->tile_row.start + 1) >> 1, 2 + (bh4 > 1));

        b_top = &rt->r[(by4 & 31) - 1 + 5][bx4];

        n_rows = scan_row(mvstack, cnt, ref, gmv, b_top,

                          bw4, w4, max_rows, bw4 >= 16 ? 4 : 1,

                          &have_newmv, &have_row_mvs);

    }

    // left

    unsigned max_cols = 0, n_cols = ~0U;

    refmvs_block *const *b_left;

    if (bx4 > rt->tile_col.start) {

        max_cols = imin((bx4 - rt->tile_col.start + 1) >> 1, 2 + (bw4 > 1));

        b_left = &rt->r[(by4 & 31) + 5];

        n_cols = scan_col(mvstack, cnt, ref, gmv, b_left,

                          bh4, h4, bx4 - 1, max_cols, bh4 >= 16 ? 4 : 1,

                          &have_newmv, &have_col_mvs);

    }

    // top/right

    if (n_rows != ~0U && edge_flags & EDGE_I444_TOP_HAS_RIGHT &&

        imax(bw4, bh4) <= 16 && bw4 + bx4 < rt->tile_col.end)

    {

        add_spatial_candidate(mvstack, cnt, 4, &b_top[bw4], ref, gmv,

                              &have_newmv, &have_row_mvs);

    }

    const int nearest_match = have_col_mvs + have_row_mvs;

    const int nearest_cnt = *cnt;

    for (int n = 0; n < nearest_cnt; n++)

        mvstack[n].weight += 640;

    // temporal

    int globalmv_ctx = rf->frm_hdr->use_ref_frame_mvs;

    if (rf->use_ref_frame_mvs) {

        const ptrdiff_t stride = rf->rp_stride;

        const int by8 = by4 >> 1, bx8 = bx4 >> 1;

        const refmvs_temporal_block *const rbi = &rt->rp_proj[(by8 & 15) * stride + bx8];

        const refmvs_temporal_block *rb = rbi;

        const int step_h = bw4 >= 16 ? 2 : 1, step_v = bh4 >= 16 ? 2 : 1;

        const int w8 = imin((w4 + 1) >> 1, 8), h8 = imin((h4 + 1) >> 1, 8);

        for (int y = 0; y < h8; y += step_v) {

            for (int x = 0; x < w8; x+= step_h) {

                add_temporal_candidate(rf, mvstack, cnt, &rb[x], ref,

                                       !(x | y) ? &globalmv_ctx : NULL, tgmv);

            }

            rb += stride * step_v;

        }

        if (imin(bw4, bh4) >= 2 && imax(bw4, bh4) < 16) {

            const int bh8 = bh4 >> 1, bw8 = bw4 >> 1;

            rb = &rbi[bh8 * stride];

            const int has_bottom = by8 + bh8 < imin(rt->tile_row.end >> 1,

                                                    (by8 & ~7) + 8);

            if (has_bottom && bx8 - 1 >= imax(rt->tile_col.start >> 1, bx8 & ~7)) {

                add_temporal_candidate(rf, mvstack, cnt, &rb[-1], ref,

                                       NULL, NULL);

            }

            if (bx8 + bw8 < imin(rt->tile_col.end >> 1, (bx8 & ~7) + 8)) {

                if (has_bottom) {

                    add_temporal_candidate(rf, mvstack, cnt, &rb[bw8], ref,

                                           NULL, NULL);

                }

                if (by8 + bh8 - 1 < imin(rt->tile_row.end >> 1, (by8 & ~7) + 8)) {

                    add_temporal_candidate(rf, mvstack, cnt, &rb[bw8 - stride],

                                           ref, NULL, NULL);

                }

            }

        }

    }

    assert(*cnt <= 8);

    // top/left (which, confusingly, is part of "secondary" references)

    int have_dummy_newmv_match;

    if ((n_rows | n_cols) != ~0U) {

        add_spatial_candidate(mvstack, cnt, 4, &b_top[-1], ref, gmv,

                              &have_dummy_newmv_match, &have_row_mvs);

    }

    // "secondary" (non-direct neighbour) top & left edges

    // what is different about secondary is that everything is now in 8x8 resolution

    for (int n = 2; n <= 3; n++) {

        if ((unsigned) n > n_rows && (unsigned) n <= max_rows) {

            n_rows += scan_row(mvstack, cnt, ref, gmv,

                               &rt->r[(((by4 & 31) - 2 * n + 1) | 1) + 5][bx4 | 1],

                               bw4, w4, 1 + max_rows - n, bw4 >= 16 ? 4 : 2,

                               &have_dummy_newmv_match, &have_row_mvs);

        }

        if ((unsigned) n > n_cols && (unsigned) n <= max_cols) {

            n_cols += scan_col(mvstack, cnt, ref, gmv, &rt->r[((by4 & 31) | 1) + 5],

                               bh4, h4, (bx4 - n * 2 + 1) | 1,

                               1 + max_cols - n, bh4 >= 16 ? 4 : 2,

                               &have_dummy_newmv_match, &have_col_mvs);

        }

    }

    assert(*cnt <= 8);

    const int ref_match_count = have_col_mvs + have_row_mvs;

    // context build-up

    int refmv_ctx, newmv_ctx;

    switch (nearest_match) {

    case 0:

        refmv_ctx = imin(2, ref_match_count);

        newmv_ctx = ref_match_count > 0;

        break;

    case 1:

        refmv_ctx = imin(ref_match_count * 3, 4);

        newmv_ctx = 3 - have_newmv;

        break;

    case 2:

        refmv_ctx = 5;

        newmv_ctx = 5 - have_newmv;

        break;

    }

    // sorting (nearest, then "secondary")

    int len = nearest_cnt;

    while (len) {

        int last = 0;

        for (int n = 1; n < len; n++) {

            if (mvstack[n - 1].weight < mvstack[n].weight) {

#define EXCHANGE(a, b) do { refmvs_candidate tmp = a; a = b; b = tmp; } while (0)

                EXCHANGE(mvstack[n - 1], mvstack[n]);

                last = n;

            }

        }

        len = last;

    }

    len = *cnt;

    while (len > nearest_cnt) {

        int last = nearest_cnt;

        for (int n = nearest_cnt + 1; n < len; n++) {

            if (mvstack[n - 1].weight < mvstack[n].weight) {

                EXCHANGE(mvstack[n - 1], mvstack[n]);

#undef EXCHANGE

                last = n;

            }

        }

        len = last;

    }

    if (ref.ref[1] > 0) {

        if (*cnt < 2) {

            const int sign0 = rf->sign_bias[ref.ref[0] - 1];

            const int sign1 = rf->sign_bias[ref.ref[1] - 1];

            const int sz4 = imin(w4, h4);

            refmvs_candidate *const same = &mvstack[*cnt];

            int same_count[4] = { 0 };

            // non-self references in top

            if (n_rows != ~0U) for (int x = 0; x < sz4;) {

                const refmvs_block *const cand_b = &b_top[x];

                add_compound_extended_candidate(same, same_count, cand_b,

                                                sign0, sign1, ref, rf->sign_bias);

                x += dav1d_block_dimensions[cand_b->bs][0];

            }

            // non-self references in left

            if (n_cols != ~0U) for (int y = 0; y < sz4;) {

                const refmvs_block *const cand_b = &b_left[y][bx4 - 1];

                add_compound_extended_candidate(same, same_count, cand_b,

                                                sign0, sign1, ref, rf->sign_bias);

                y += dav1d_block_dimensions[cand_b->bs][1];

            }

            refmvs_candidate *const diff = &same[2];

            const int *const diff_count = &same_count[2];

            // merge together

            for (int n = 0; n < 2; n++) {

                int m = same_count[n];

                if (m >= 2) continue;

                const int l = diff_count[n];

                if (l) {

                    same[m].mv.mv[n] = diff[0].mv.mv[n];

                    if (++m == 2) continue;

                    if (l == 2) {

                        same[1].mv.mv[n] = diff[1].mv.mv[n];

                        continue;

                    }

                }

                do {

                    same[m].mv.mv[n] = tgmv[n];

                } while (++m < 2);

            }

            // if the first extended was the same as the non-extended one,

            // then replace it with the second extended one

            int n = *cnt;

            if (n == 1 && mvstack[0].mv.n == same[0].mv.n)

                mvstack[1].mv = mvstack[2].mv;

            do {

                mvstack[n].weight = 2;

            } while (++n < 2);

            *cnt = 2;

        }

        // clamping

        const int left = -(bx4 + bw4 + 4) * 4 * 8;

        const int right = (rf->iw4 - bx4 + 4) * 4 * 8;

        const int top = -(by4 + bh4 + 4) * 4 * 8;

        const int bottom = (rf->ih4 - by4 + 4) * 4 * 8;

        const int n_refmvs = *cnt;

        int n = 0;

        do {

            mvstack[n].mv.mv[0].x = iclip(mvstack[n].mv.mv[0].x, left, right);

            mvstack[n].mv.mv[0].y = iclip(mvstack[n].mv.mv[0].y, top, bottom);

            mvstack[n].mv.mv[1].x = iclip(mvstack[n].mv.mv[1].x, left, right);

            mvstack[n].mv.mv[1].y = iclip(mvstack[n].mv.mv[1].y, top, bottom);

        } while (++n < n_refmvs);

        switch (refmv_ctx >> 1) {

        case 0:

            *ctx = imin(newmv_ctx, 1);

            break;

        case 1:

            *ctx = 1 + imin(newmv_ctx, 3);

            break;

        case 2:

            *ctx = iclip(3 + newmv_ctx, 4, 7);

            break;

        }

        return;

    } else if (*cnt < 2 && ref.ref[0] > 0) {

        const int sign = rf->sign_bias[ref.ref[0] - 1];

        const int sz4 = imin(w4, h4);

        // non-self references in top

        if (n_rows != ~0U) for (int x = 0; x < sz4 && *cnt < 2;) {

            const refmvs_block *const cand_b = &b_top[x];

            add_single_extended_candidate(mvstack, cnt, cand_b, sign, rf->sign_bias);

            x += dav1d_block_dimensions[cand_b->bs][0];

        }

        // non-self references in left

        if (n_cols != ~0U) for (int y = 0; y < sz4 && *cnt < 2;) {

            const refmvs_block *const cand_b = &b_left[y][bx4 - 1];

            add_single_extended_candidate(mvstack, cnt, cand_b, sign, rf->sign_bias);

            y += dav1d_block_dimensions[cand_b->bs][1];

        }

    }

    assert(*cnt <= 8);

    // clamping

    int n_refmvs = *cnt;

    if (n_refmvs) {

        const int left = -(bx4 + bw4 + 4) * 4 * 8;

        const int right = (rf->iw4 - bx4 + 4) * 4 * 8;

        const int top = -(by4 + bh4 + 4) * 4 * 8;

        const int bottom = (rf->ih4 - by4 + 4) * 4 * 8;

        int n = 0;

        do {

            mvstack[n].mv.mv[0].x = iclip(mvstack[n].mv.mv[0].x, left, right);

            mvstack[n].mv.mv[0].y = iclip(mvstack[n].mv.mv[0].y, top, bottom);

        } while (++n < n_refmvs);

    }

    for (int n = *cnt; n < 2; n++)

        mvstack[n].mv.mv[0] = tgmv[0];

    *ctx = (refmv_ctx << 4) | (globalmv_ctx << 3) | newmv_ctx;

}

void dav1d_refmvs_tile_sbrow_init(refmvs_tile *const rt, const refmvs_frame *const rf,

                                  const int tile_col_start4, const int tile_col_end4,

                                  const int tile_row_start4, const int tile_row_end4,

                                  const int sby, int tile_row_idx, const int pass)

{

    if (rf->n_tile_threads == 1) tile_row_idx = 0;

    rt->rp_proj = &rf->rp_proj[16 * rf->rp_stride * tile_row_idx];

    const ptrdiff_t r_stride = rf->rp_stride * 2;

    const ptrdiff_t pass_off = (rf->n_frame_threads > 1 && pass == 2) ?

        35 * 2 * rf->n_blocks : 0;

    refmvs_block *r = &rf->r[35 * r_stride * tile_row_idx + pass_off];

    const int sbsz = rf->sbsz;

    const int off = (sbsz * sby) & 16;

    for (int i = 0; i < sbsz; i++, r += r_stride)

        rt->r[off + 5 + i] = r;

    rt->r[off + 0] = r;

    r += r_stride;

    rt->r[off + 1] = NULL;

    rt->r[off + 2] = r;

    r += r_stride;

    rt->r[off + 3] = NULL;

    rt->r[off + 4] = r;

    if (sby & 1) {

#define EXCHANGE(a, b) do { void *const tmp = a; a = b; b = tmp; } while (0)

        EXCHANGE(rt->r[off + 0], rt->r[off + sbsz + 0]);

        EXCHANGE(rt->r[off + 2], rt->r[off + sbsz + 2]);

        EXCHANGE(rt->r[off + 4], rt->r[off + sbsz + 4]);

#undef EXCHANGE

    }

    rt->rf = rf;

    rt->tile_row.start = tile_row_start4;

    rt->tile_row.end = imin(tile_row_end4, rf->ih4);

    rt->tile_col.start = tile_col_start4;

    rt->tile_col.end = imin(tile_col_end4, rf->iw4);

}

static void load_tmvs_c(const refmvs_frame *const rf, int tile_row_idx,

                        const int col_start8, const int col_end8,

                        const int row_start8, int row_end8)

{

    if (rf->n_tile_threads == 1) tile_row_idx = 0;

    assert(row_start8 >= 0);

    assert((unsigned) (row_end8 - row_start8) <= 16U);

    row_end8 = imin(row_end8, rf->ih8);

    const int col_start8i = imax(col_start8 - 8, 0);

    const int col_end8i = imin(col_end8 + 8, rf->iw8);

    const ptrdiff_t stride = rf->rp_stride;

    refmvs_temporal_block *rp_proj =

        &rf->rp_proj[16 * stride * tile_row_idx + (row_start8 & 15) * stride];

    for (int y = row_start8; y < row_end8; y++) {

        for (int x = col_start8; x < col_end8; x++)

            rp_proj[x].mv.n = INVALID_MV;

        rp_proj += stride;

    }

    rp_proj = &rf->rp_proj[16 * stride * tile_row_idx];

    for (int n = 0; n < rf->n_mfmvs; n++) {

        const int ref2cur = rf->mfmv_ref2cur[n];

        if (ref2cur == INVALID_REF2CUR) continue;

        const int ref = rf->mfmv_ref[n];

        const int ref_sign = ref - 4;

        const refmvs_temporal_block *r = &rf->rp_ref[ref][row_start8 * stride];

        for (int y = row_start8; y < row_end8; y++) {

            const int y_sb_align = y & ~7;

            const int y_proj_start = imax(y_sb_align, row_start8);

            const int y_proj_end = imin(y_sb_align + 8, row_end8);

            for (int x = col_start8i; x < col_end8i; x++) {

                const refmvs_temporal_block *rb = &r[x];

                const int b_ref = rb->ref;

                if (!b_ref) continue;

                const int ref2ref = rf->mfmv_ref2ref[n][b_ref - 1];

                if (!ref2ref) continue;

                const mv b_mv = rb->mv;

                const mv offset = mv_projection(b_mv, ref2cur, ref2ref);

                int pos_x = x + apply_sign(abs(offset.x) >> 6,

                                           offset.x ^ ref_sign);

                const int pos_y = y + apply_sign(abs(offset.y) >> 6,

                                                 offset.y ^ ref_sign);

                if (pos_y >= y_proj_start && pos_y < y_proj_end) {

                    const ptrdiff_t pos = (pos_y & 15) * stride;

                    for (;;) {

                        const int x_sb_align = x & ~7;

                        if (pos_x >= imax(x_sb_align - 8, col_start8) &&

                            pos_x < imin(x_sb_align + 16, col_end8))

                        {

                            rp_proj[pos + pos_x].mv = rb->mv;

                            rp_proj[pos + pos_x].ref = ref2ref;

                        }

                        if (++x >= col_end8i) break;

                        rb++;

                        if (rb->ref != b_ref || rb->mv.n != b_mv.n) break;

                        pos_x++;

                    }

                } else {

                    for (;;) {

                        if (++x >= col_end8i) break;

                        rb++;

                        if (rb->ref != b_ref || rb->mv.n != b_mv.n) break;

                    }

                }

                x--;

            }

            r += stride;

        }

    }

}

static void save_tmvs_c(refmvs_temporal_block *rp, const ptrdiff_t stride,

                        refmvs_block *const *const rr,

                        const uint8_t *const ref_sign,

                        const int col_end8, const int row_end8,

                        const int col_start8, const int row_start8)

{

    for (int y = row_start8; y < row_end8; y++) {

        const refmvs_block *const b = rr[(y & 15) * 2];

        for (int x = col_start8; x < col_end8;) {

            const refmvs_block *const cand_b = &b[x * 2 + 1];

            const int bw8 = (dav1d_block_dimensions[cand_b->bs][0] + 1) >> 1;

            if (cand_b->ref.ref[1] > 0 && ref_sign[cand_b->ref.ref[1] - 1] &&

                (abs(cand_b->mv.mv[1].y) | abs(cand_b->mv.mv[1].x)) < 4096)

            {

                for (int n = 0; n < bw8; n++, x++)

                    rp[x] = (refmvs_temporal_block) { .mv = cand_b->mv.mv[1],

                                                      .ref = cand_b->ref.ref[1] };

            } else if (cand_b->ref.ref[0] > 0 && ref_sign[cand_b->ref.ref[0] - 1] &&

                       (abs(cand_b->mv.mv[0].y) | abs(cand_b->mv.mv[0].x)) < 4096)

            {

                for (int n = 0; n < bw8; n++, x++)

                    rp[x] = (refmvs_temporal_block) { .mv = cand_b->mv.mv[0],

                                                      .ref = cand_b->ref.ref[0] };

            } else {

                for (int n = 0; n < bw8; n++, x++) {

                    rp[x].mv.n = 0;

                    rp[x].ref = 0; // "invalid"

                }

            }

        }

        rp += stride;

    }

}

int dav1d_refmvs_init_frame(refmvs_frame *const rf,

                            const Dav1dSequenceHeader *const seq_hdr,

                            const Dav1dFrameHeader *const frm_hdr,

                            const uint8_t ref_poc[7],

                            refmvs_temporal_block *const rp,

                            const uint8_t ref_ref_poc[7][7],

                            /*const*/ refmvs_temporal_block *const rp_ref[7],

                            const int n_tile_threads, const int n_frame_threads)

{

    const int rp_stride = ((frm_hdr->width[0] + 127) & ~127) >> 3;

    const int n_tile_rows = n_tile_threads > 1 ? frm_hdr->tiling.rows : 1;

    const int n_blocks = rp_stride * n_tile_rows;

    rf->sbsz = 16 << seq_hdr->sb128;

    rf->frm_hdr = frm_hdr;

    rf->iw8 = (frm_hdr->width[0] + 7) >> 3;

    rf->ih8 = (frm_hdr->height + 7) >> 3;

    rf->iw4 = rf->iw8 << 1;

    rf->ih4 = rf->ih8 << 1;

    rf->rp = rp;

    rf->rp_stride = rp_stride;

    rf->n_tile_threads = n_tile_threads;

    rf->n_frame_threads = n_frame_threads;

    if (n_blocks != rf->n_blocks) {

        const size_t r_sz = sizeof(*rf->r) * 35 * 2 * n_blocks * (1 + (n_frame_threads > 1));

        const size_t rp_proj_sz = sizeof(*rf->rp_proj) * 16 * n_blocks;

        /* Note that sizeof(*rf->r) == 12, but it's accessed using 16-byte unaligned

         * loads in save_tmvs() asm which can overread 4 bytes into rp_proj. */

        dav1d_free_aligned(rf->r);

        rf->r = dav1d_alloc_aligned(ALLOC_REFMVS, r_sz + rp_proj_sz, 64);

        if (!rf->r) {

            rf->n_blocks = 0;

            return DAV1D_ERR(ENOMEM);

        }

        rf->rp_proj = (refmvs_temporal_block*)((uintptr_t)rf->r + r_sz);

        rf->n_blocks = n_blocks;

    }

    const int poc = frm_hdr->frame_offset;

    for (int i = 0; i < 7; i++) {

        const int poc_diff = get_poc_diff(seq_hdr->order_hint_n_bits,

                                          ref_poc[i], poc);

        rf->sign_bias[i] = poc_diff > 0;

        rf->mfmv_sign[i] = poc_diff < 0;

        rf->pocdiff[i] = iclip(get_poc_diff(seq_hdr->order_hint_n_bits,

                                            poc, ref_poc[i]), -31, 31);

    }

    // temporal MV setup

    rf->n_mfmvs = 0;

    rf->rp_ref = rp_ref;