avcodec/hevc_mvs: Pass HEVCLocalContext when slice-threading

The HEVC decoder has both HEVCContext and HEVCLocalContext
structures. The latter is supposed to be the structure
containing the per-slicethread state.

Yet that is not how it is handled in practice: Each HEVCLocalContext
has a unique HEVCContext allocated for it and each of these
coincides except in exactly one field: The corresponding
HEVCLocalContext. This makes it possible to pass the HEVCContext
everywhere where logically a HEVCLocalContext should be used.

This commit stops doing this for lavc/hevc_mvs.c; it also constifies
everything that is possible in order to ensure that no slice thread
accidentally modifies the main HEVCContext state.

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

3 files changed, 45 insertions, 44 deletions

diff --git a/libavcodec/hevc_mvs.c b/libavcodec/hevc_mvs.c
index 516e4a6b7a..bcf6ec3abc 100644
--- a/libavcodec/hevc_mvs.c
+++ b/libavcodec/hevc_mvs.c
@@ -40,10 +40,10 @@ static const uint8_t l0_l1_cand_idx[12][2] = {
     { 3, 2, },
 };
 
-void ff_hevc_set_neighbour_available(HEVCContext *s, int x0, int y0,
+void ff_hevc_set_neighbour_available(HEVCLocalContext *lc, int x0, int y0,
                                      int nPbW, int nPbH)
 {
-    HEVCLocalContext *lc = s->HEVClc;
+    const HEVCContext *const s = lc->parent;
     int x0b = av_mod_uintp2(x0, s->ps.sps->log2_ctb_size);
     int y0b = av_mod_uintp2(y0, s->ps.sps->log2_ctb_size);
 
@@ -62,7 +62,7 @@ void ff_hevc_set_neighbour_available(HEVCContext *s, int x0, int y0,
 /*
  * 6.4.1 Derivation process for z-scan order block availability
  */
-static av_always_inline int z_scan_block_avail(HEVCContext *s, int xCurr, int yCurr,
+static av_always_inline int z_scan_block_avail(const HEVCContext *s, int xCurr, int yCurr,
                               int xN, int yN)
 {
 #define MIN_TB_ADDR_ZS(x, y)                                            \
@@ -84,7 +84,7 @@ static av_always_inline int z_scan_block_avail(HEVCContext *s, int xCurr, int yC
 }
 
 //check if the two luma locations belong to the same motion estimation region
-static av_always_inline int is_diff_mer(HEVCContext *s, int xN, int yN, int xP, int yP)
+static av_always_inline int is_diff_mer(const HEVCContext *s, int xN, int yN, int xP, int yP)
 {
     uint8_t plevel = s->ps.pps->log2_parallel_merge_level;
 
@@ -161,11 +161,11 @@ static int check_mvset(Mv *mvLXCol, const Mv *mvCol,
                 refPicList_col, L ## l, temp_col.ref_idx[l])
 
 // derive the motion vectors section 8.5.3.1.8
-static int derive_temporal_colocated_mvs(HEVCContext *s, MvField temp_col,
+static int derive_temporal_colocated_mvs(const HEVCContext *s, MvField temp_col,
                                          int refIdxLx, Mv *mvLXCol, int X,
                                          int colPic, const RefPicList *refPicList_col)
 {
-    RefPicList *refPicList = s->ref->refPicList;
+    const RefPicList *refPicList = s->ref->refPicList;
 
     if (temp_col.pred_flag == PF_INTRA)
         return 0;
@@ -216,11 +216,11 @@ static int derive_temporal_colocated_mvs(HEVCContext *s, MvField temp_col,
 /*
  * 8.5.3.1.7  temporal luma motion vector prediction
  */
-static int temporal_luma_motion_vector(HEVCContext *s, int x0, int y0,
+static int temporal_luma_motion_vector(const HEVCContext *s, int x0, int y0,
                                        int nPbW, int nPbH, int refIdxLx,
                                        Mv *mvLXCol, int X)
 {
-    MvField *tab_mvf;
+    const MvField *tab_mvf;
     MvField temp_col;
     int x, y, x_pu, y_pu;
     int min_pu_width = s->ps.sps->min_pu_width;
@@ -283,16 +283,16 @@ static int temporal_luma_motion_vector(HEVCContext *s, int x0, int y0,
 /*
  * 8.5.3.1.2  Derivation process for spatial merging candidates
  */
-static void derive_spatial_merge_candidates(HEVCContext *s, int x0, int y0,
+static void derive_spatial_merge_candidates(HEVCLocalContext *lc, const HEVCContext *s,
+                                            int x0, int y0,
                                             int nPbW, int nPbH,
                                             int log2_cb_size,
                                             int singleMCLFlag, int part_idx,
                                             int merge_idx,
                                             struct MvField mergecandlist[])
 {
-    HEVCLocalContext *lc   = s->HEVClc;
-    RefPicList *refPicList = s->ref->refPicList;
-    MvField *tab_mvf       = s->ref->tab_mvf;
+    const RefPicList *refPicList = s->ref->refPicList;
+    const MvField *tab_mvf       = s->ref->tab_mvf;
 
     const int min_pu_width = s->ps.sps->min_pu_width;
 
@@ -477,16 +477,16 @@ static void derive_spatial_merge_candidates(HEVCContext *s, int x0, int y0,
 /*
  * 8.5.3.1.1 Derivation process of luma Mvs for merge mode
  */
-void ff_hevc_luma_mv_merge_mode(HEVCContext *s, int x0, int y0, int nPbW,
+void ff_hevc_luma_mv_merge_mode(HEVCLocalContext *lc, int x0, int y0, int nPbW,
                                 int nPbH, int log2_cb_size, int part_idx,
                                 int merge_idx, MvField *mv)
 {
+    const HEVCContext *const s = lc->parent;
     int singleMCLFlag = 0;
     int nCS = 1 << log2_cb_size;
     MvField mergecand_list[MRG_MAX_NUM_CANDS];
     int nPbW2 = nPbW;
     int nPbH2 = nPbH;
-    HEVCLocalContext *lc = s->HEVClc;
 
     if (s->ps.pps->log2_parallel_merge_level > 2 && nCS == 8) {
         singleMCLFlag = 1;
@@ -497,8 +497,8 @@ void ff_hevc_luma_mv_merge_mode(HEVCContext *s, int x0, int y0, int nPbW,
         part_idx      = 0;
     }
 
-    ff_hevc_set_neighbour_available(s, x0, y0, nPbW, nPbH);
-    derive_spatial_merge_candidates(s, x0, y0, nPbW, nPbH, log2_cb_size,
+    ff_hevc_set_neighbour_available(lc, x0, y0, nPbW, nPbH);
+    derive_spatial_merge_candidates(lc, s, x0, y0, nPbW, nPbH, log2_cb_size,
                                     singleMCLFlag, part_idx,
                                     merge_idx, mergecand_list);
 
@@ -510,12 +510,12 @@ void ff_hevc_luma_mv_merge_mode(HEVCContext *s, int x0, int y0, int nPbW,
     *mv = mergecand_list[merge_idx];
 }
 
-static av_always_inline void dist_scale(HEVCContext *s, Mv *mv,
+static av_always_inline void dist_scale(const HEVCContext *s, Mv *mv,
                                         int min_pu_width, int x, int y,
                                         int elist, int ref_idx_curr, int ref_idx)
 {
-    RefPicList *refPicList = s->ref->refPicList;
-    MvField *tab_mvf       = s->ref->tab_mvf;
+    const RefPicList *refPicList = s->ref->refPicList;
+    const MvField *tab_mvf       = s->ref->tab_mvf;
     int ref_pic_elist      = refPicList[elist].list[TAB_MVF(x, y).ref_idx[elist]];
     int ref_pic_curr       = refPicList[ref_idx_curr].list[ref_idx];
 
@@ -527,13 +527,13 @@ static av_always_inline void dist_scale(HEVCContext *s, Mv *mv,
     }
 }
 
-static int mv_mp_mode_mx(HEVCContext *s, int x, int y, int pred_flag_index,
+static int mv_mp_mode_mx(const HEVCContext *s, int x, int y, int pred_flag_index,
                          Mv *mv, int ref_idx_curr, int ref_idx)
 {
-    MvField *tab_mvf = s->ref->tab_mvf;
+    const MvField *tab_mvf = s->ref->tab_mvf;
     int min_pu_width = s->ps.sps->min_pu_width;
 
-    RefPicList *refPicList = s->ref->refPicList;
+    const RefPicList *refPicList = s->ref->refPicList;
 
     if (((TAB_MVF(x, y).pred_flag) & (1 << pred_flag_index)) &&
         refPicList[pred_flag_index].list[TAB_MVF(x, y).ref_idx[pred_flag_index]] == refPicList[ref_idx_curr].list[ref_idx]) {
@@ -543,13 +543,13 @@ static int mv_mp_mode_mx(HEVCContext *s, int x, int y, int pred_flag_index,
     return 0;
 }
 
-static int mv_mp_mode_mx_lt(HEVCContext *s, int x, int y, int pred_flag_index,
+static int mv_mp_mode_mx_lt(const HEVCContext *s, int x, int y, int pred_flag_index,
                             Mv *mv, int ref_idx_curr, int ref_idx)
 {
-    MvField *tab_mvf = s->ref->tab_mvf;
+    const MvField *tab_mvf = s->ref->tab_mvf;
     int min_pu_width = s->ps.sps->min_pu_width;
 
-    RefPicList *refPicList = s->ref->refPicList;
+    const RefPicList *refPicList = s->ref->refPicList;
 
     if ((TAB_MVF(x, y).pred_flag) & (1 << pred_flag_index)) {
         int currIsLongTerm     = refPicList[ref_idx_curr].isLongTerm[ref_idx];
@@ -580,13 +580,13 @@ static int mv_mp_mode_mx_lt(HEVCContext *s, int x, int y, int pred_flag_index,
                      (y ## v) >> s->ps.sps->log2_min_pu_size,      \
                      pred, &mx, ref_idx_curr, ref_idx)
 
-void ff_hevc_luma_mv_mvp_mode(HEVCContext *s, int x0, int y0, int nPbW,
+void ff_hevc_luma_mv_mvp_mode(HEVCLocalContext *lc, int x0, int y0, int nPbW,
                               int nPbH, int log2_cb_size, int part_idx,
                               int merge_idx, MvField *mv,
                               int mvp_lx_flag, int LX)
 {
-    HEVCLocalContext *lc = s->HEVClc;
-    MvField *tab_mvf = s->ref->tab_mvf;
+    const HEVCContext *const s = lc->parent;
+    const MvField *const tab_mvf = s->ref->tab_mvf;
     int isScaledFlag_L0 = 0;
     int availableFlagLXA0 = 1;
     int availableFlagLXB0 = 1;
diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
index 846077b6ab..5307381d8b 100644
--- a/libavcodec/hevcdec.c
+++ b/libavcodec/hevcdec.c
@@ -1107,7 +1107,7 @@ static int hls_transform_unit(HEVCContext *s, int x0, int y0,
 
     if (lc->cu.pred_mode == MODE_INTRA) {
         int trafo_size = 1 << log2_trafo_size;
-        ff_hevc_set_neighbour_available(s, x0, y0, trafo_size, trafo_size);
+        ff_hevc_set_neighbour_available(lc, x0, y0, trafo_size, trafo_size);
 
         s->hpc.intra_pred[log2_trafo_size - 2](s, x0, y0, 0);
     }
@@ -1194,7 +1194,7 @@ static int hls_transform_unit(HEVCContext *s, int x0, int y0,
             }
             for (i = 0; i < (s->ps.sps->chroma_format_idc == 2 ? 2 : 1); i++) {
                 if (lc->cu.pred_mode == MODE_INTRA) {
-                    ff_hevc_set_neighbour_available(s, x0, y0 + (i << log2_trafo_size_c), trafo_size_h, trafo_size_v);
+                    ff_hevc_set_neighbour_available(lc, x0, y0 + (i << log2_trafo_size_c), trafo_size_h, trafo_size_v);
                     s->hpc.intra_pred[log2_trafo_size_c - 2](s, x0, y0 + (i << log2_trafo_size_c), 1);
                 }
                 if (cbf_cb[i])
@@ -1223,7 +1223,8 @@ static int hls_transform_unit(HEVCContext *s, int x0, int y0,
             }
             for (i = 0; i < (s->ps.sps->chroma_format_idc == 2 ? 2 : 1); i++) {
                 if (lc->cu.pred_mode == MODE_INTRA) {
-                    ff_hevc_set_neighbour_available(s, x0, y0 + (i << log2_trafo_size_c), trafo_size_h, trafo_size_v);
+                    ff_hevc_set_neighbour_available(lc, x0, y0 + (i << log2_trafo_size_c),
+                                                    trafo_size_h, trafo_size_v);
                     s->hpc.intra_pred[log2_trafo_size_c - 2](s, x0, y0 + (i << log2_trafo_size_c), 2);
                 }
                 if (cbf_cr[i])
@@ -1251,7 +1252,7 @@ static int hls_transform_unit(HEVCContext *s, int x0, int y0,
             int trafo_size_v = 1 << (log2_trafo_size + s->ps.sps->vshift[1]);
             for (i = 0; i < (s->ps.sps->chroma_format_idc == 2 ? 2 : 1); i++) {
                 if (lc->cu.pred_mode == MODE_INTRA) {
-                    ff_hevc_set_neighbour_available(s, xBase, yBase + (i << log2_trafo_size),
+                    ff_hevc_set_neighbour_available(lc, xBase, yBase + (i << log2_trafo_size),
                                                     trafo_size_h, trafo_size_v);
                     s->hpc.intra_pred[log2_trafo_size - 2](s, xBase, yBase + (i << log2_trafo_size), 1);
                 }
@@ -1261,7 +1262,7 @@ static int hls_transform_unit(HEVCContext *s, int x0, int y0,
             }
             for (i = 0; i < (s->ps.sps->chroma_format_idc == 2 ? 2 : 1); i++) {
                 if (lc->cu.pred_mode == MODE_INTRA) {
-                    ff_hevc_set_neighbour_available(s, xBase, yBase + (i << log2_trafo_size),
+                    ff_hevc_set_neighbour_available(lc, xBase, yBase + (i << log2_trafo_size),
                                                 trafo_size_h, trafo_size_v);
                     s->hpc.intra_pred[log2_trafo_size - 2](s, xBase, yBase + (i << log2_trafo_size), 2);
                 }
@@ -1274,11 +1275,11 @@ static int hls_transform_unit(HEVCContext *s, int x0, int y0,
         if (log2_trafo_size > 2 || s->ps.sps->chroma_format_idc == 3) {
             int trafo_size_h = 1 << (log2_trafo_size_c + s->ps.sps->hshift[1]);
             int trafo_size_v = 1 << (log2_trafo_size_c + s->ps.sps->vshift[1]);
-            ff_hevc_set_neighbour_available(s, x0, y0, trafo_size_h, trafo_size_v);
+            ff_hevc_set_neighbour_available(lc, x0, y0, trafo_size_h, trafo_size_v);
             s->hpc.intra_pred[log2_trafo_size_c - 2](s, x0, y0, 1);
             s->hpc.intra_pred[log2_trafo_size_c - 2](s, x0, y0, 2);
             if (s->ps.sps->chroma_format_idc == 2) {
-                ff_hevc_set_neighbour_available(s, x0, y0 + (1 << log2_trafo_size_c),
+                ff_hevc_set_neighbour_available(lc, x0, y0 + (1 << log2_trafo_size_c),
                                                 trafo_size_h, trafo_size_v);
                 s->hpc.intra_pred[log2_trafo_size_c - 2](s, x0, y0 + (1 << log2_trafo_size_c), 1);
                 s->hpc.intra_pred[log2_trafo_size_c - 2](s, x0, y0 + (1 << log2_trafo_size_c), 2);
@@ -1286,12 +1287,12 @@ static int hls_transform_unit(HEVCContext *s, int x0, int y0,
         } else if (blk_idx == 3) {
             int trafo_size_h = 1 << (log2_trafo_size + 1);
             int trafo_size_v = 1 << (log2_trafo_size + s->ps.sps->vshift[1]);
-            ff_hevc_set_neighbour_available(s, xBase, yBase,
+            ff_hevc_set_neighbour_available(lc, xBase, yBase,
                                             trafo_size_h, trafo_size_v);
             s->hpc.intra_pred[log2_trafo_size - 2](s, xBase, yBase, 1);
             s->hpc.intra_pred[log2_trafo_size - 2](s, xBase, yBase, 2);
             if (s->ps.sps->chroma_format_idc == 2) {
-                ff_hevc_set_neighbour_available(s, xBase, yBase + (1 << (log2_trafo_size)),
+                ff_hevc_set_neighbour_available(lc, xBase, yBase + (1 << (log2_trafo_size)),
                                                 trafo_size_h, trafo_size_v);
                 s->hpc.intra_pred[log2_trafo_size - 2](s, xBase, yBase + (1 << (log2_trafo_size)), 1);
                 s->hpc.intra_pred[log2_trafo_size - 2](s, xBase, yBase + (1 << (log2_trafo_size)), 2);
@@ -1822,7 +1823,7 @@ static void hevc_luma_mv_mvp_mode(HEVCContext *s, int x0, int y0, int nPbW,
     enum InterPredIdc inter_pred_idc = PRED_L0;
     int mvp_flag;
 
-    ff_hevc_set_neighbour_available(s, x0, y0, nPbW, nPbH);
+    ff_hevc_set_neighbour_available(lc, x0, y0, nPbW, nPbH);
     mv->pred_flag = 0;
     if (s->sh.slice_type == HEVC_SLICE_B)
         inter_pred_idc = ff_hevc_inter_pred_idc_decode(s, nPbW, nPbH);
@@ -1834,7 +1835,7 @@ static void hevc_luma_mv_mvp_mode(HEVCContext *s, int x0, int y0, int nPbW,
         mv->pred_flag = PF_L0;
         ff_hevc_hls_mvd_coding(s, x0, y0, 0);
         mvp_flag = ff_hevc_mvp_lx_flag_decode(s);
-        ff_hevc_luma_mv_mvp_mode(s, x0, y0, nPbW, nPbH, log2_cb_size,
+        ff_hevc_luma_mv_mvp_mode(lc, x0, y0, nPbW, nPbH, log2_cb_size,
                                  part_idx, merge_idx, mv, mvp_flag, 0);
         mv->mv[0].x += lc->pu.mvd.x;
         mv->mv[0].y += lc->pu.mvd.y;
@@ -1852,7 +1853,7 @@ static void hevc_luma_mv_mvp_mode(HEVCContext *s, int x0, int y0, int nPbW,
 
         mv->pred_flag += PF_L1;
         mvp_flag = ff_hevc_mvp_lx_flag_decode(s);
-        ff_hevc_luma_mv_mvp_mode(s, x0, y0, nPbW, nPbH, log2_cb_size,
+        ff_hevc_luma_mv_mvp_mode(lc, x0, y0, nPbW, nPbH, log2_cb_size,
                                  part_idx, merge_idx, mv, mvp_flag, 1);
         mv->mv[1].x += lc->pu.mvd.x;
         mv->mv[1].y += lc->pu.mvd.y;
@@ -1896,7 +1897,7 @@ static void hls_prediction_unit(HEVCContext *s, int x0, int y0,
         else
             merge_idx = 0;
 
-        ff_hevc_luma_mv_merge_mode(s, x0, y0, nPbW, nPbH, log2_cb_size,
+        ff_hevc_luma_mv_merge_mode(lc, x0, y0, nPbW, nPbH, log2_cb_size,
                                    partIdx, merge_idx, &current_mv);
     } else {
         hevc_luma_mv_mvp_mode(s, x0, y0, nPbW, nPbH, log2_cb_size,
diff --git a/libavcodec/hevcdec.h b/libavcodec/hevcdec.h
index 271a55df2f..3bb3fdb90a 100644
--- a/libavcodec/hevcdec.h
+++ b/libavcodec/hevcdec.h
@@ -667,12 +667,12 @@ void ff_hevc_bump_frame(HEVCContext *s);
 
 void ff_hevc_unref_frame(HEVCContext *s, HEVCFrame *frame, int flags);
 
-void ff_hevc_set_neighbour_available(HEVCContext *s, int x0, int y0,
+void ff_hevc_set_neighbour_available(HEVCLocalContext *lc, int x0, int y0,
                                      int nPbW, int nPbH);
-void ff_hevc_luma_mv_merge_mode(HEVCContext *s, int x0, int y0,
+void ff_hevc_luma_mv_merge_mode(HEVCLocalContext *lc, int x0, int y0,
                                 int nPbW, int nPbH, int log2_cb_size,
                                 int part_idx, int merge_idx, MvField *mv);
-void ff_hevc_luma_mv_mvp_mode(HEVCContext *s, int x0, int y0,
+void ff_hevc_luma_mv_mvp_mode(HEVCLocalContext *lc, int x0, int y0,
                               int nPbW, int nPbH, int log2_cb_size,
                               int part_idx, int merge_idx,
                               MvField *mv, int mvp_lx_flag, int LX);