avcodec/smacker: Use symbols table

Up until now, the return value of get_vlc2() has been used as an index
in an array that contained the value one is really interested in. Yet
since b613bacca9c256f1483c46847f713e47a0e9a5f6 this is no longer
necessary, as one can store the value that is right now stored in the
array in the VLC internal table.

This also means that all the information from the eight bit Huffman trees
are now stored in the corresponding VLC table; this will enable us to
remove several allocations lateron.

This improved performance: For GCC 9 the time for one call of
smka_decode_frame() for the sample from ticket #2425 decreased from
1811706 to 1794494 decicycles; for Clang 9 the number went from 1471663
to 1449420 decicycles.

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

1 files changed, 30 insertions, 24 deletions

diff --git a/libavcodec/smacker.c b/libavcodec/smacker.c
index c1928e3908..15c8856e69 100644
--- a/libavcodec/smacker.c
+++ b/libavcodec/smacker.c
@@ -78,7 +78,7 @@ typedef struct DBCtx {
     int current, length;
     int *values;
     VLC *v1, *v2;
-    const uint8_t *recode1, *recode2;
+    uint8_t vals[2];
     int escapes[3];
     int *last;
 } DBCtx;
@@ -156,9 +156,11 @@ static int smacker_decode_bigtree(GetBitContext *gb, DBCtx *ctx, int length)
         return AVERROR_INVALIDDATA;
     if(!get_bits1(gb)){ //Leaf
         int val, i1, i2;
-        i1 = ctx->v1->table ? get_vlc2(gb, ctx->v1->table, SMKTREE_BITS, 3) : 0;
-        i2 = ctx->v2->table ? get_vlc2(gb, ctx->v2->table, SMKTREE_BITS, 3) : 0;
-        val = ctx->recode1[i1] | (ctx->recode2[i2] << 8);
+        i1 = ctx->v1->table ? get_vlc2(gb, ctx->v1->table, SMKTREE_BITS, 3)
+                            : ctx->vals[0];
+        i2 = ctx->v2->table ? get_vlc2(gb, ctx->v2->table, SMKTREE_BITS, 3)
+                            : ctx->vals[1];
+        val = i1 | (i2 << 8);
         if(val == ctx->escapes[0]) {
             ctx->last[0] = ctx->current;
             val = 0;
@@ -218,7 +220,7 @@ static int smacker_decode_header_tree(SmackVContext *smk, GetBitContext *gb, int
             goto error;
         }
         if (!get_bits1(gb)) {
-            h[i].values[0] = 0;
+            ctx.vals[i] = 0;
             av_log(smk->avctx, AV_LOG_ERROR, "Skipping %s bytes tree\n",
                    i ? "high" : "low");
             continue;
@@ -228,15 +230,17 @@ static int smacker_decode_header_tree(SmackVContext *smk, GetBitContext *gb, int
             goto error;
         skip_bits1(gb);
         if (h[i].current > 1) {
-            err = init_vlc(&vlc[i], SMKTREE_BITS, h[i].current,
+            err = ff_init_vlc_sparse(&vlc[i], SMKTREE_BITS, h[i].current,
                            INIT_VLC_DEFAULT_SIZES(h[i].lengths),
                            INIT_VLC_DEFAULT_SIZES(h[i].bits),
+                                     INIT_VLC_DEFAULT_SIZES(h[i].values),
                            INIT_VLC_LE);
             if (err < 0) {
                 av_log(smk->avctx, AV_LOG_ERROR, "Cannot build VLC table\n");
                 goto error;
             }
-        }
+        } else
+            ctx.vals[i] = h[i].values[0];
     }
 
     escapes[0]  = get_bits(gb, 16);
@@ -250,8 +254,6 @@ static int smacker_decode_header_tree(SmackVContext *smk, GetBitContext *gb, int
     ctx.escapes[2] = escapes[2];
     ctx.v1 = &vlc[0];
     ctx.v2 = &vlc[1];
-    ctx.recode1 = h[0].values;
-    ctx.recode2 = h[1].values;
     ctx.last = last;
     ctx.length  = (size + 3) >> 2;
     ctx.current = 0;
@@ -605,6 +607,7 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data,
     VLC vlc[4]       = { { 0 } };
     int16_t *samples;
     uint8_t *samples8;
+    uint8_t values[4];
     int val;
     int i, res, ret;
     int unp_size;
@@ -670,14 +673,17 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data,
             goto error;
         skip_bits1(&gb);
         if(h[i].current > 1) {
-            ret = init_vlc(&vlc[i], SMKTREE_BITS, h[i].current,
+            ret = ff_init_vlc_sparse(&vlc[i], SMKTREE_BITS, h[i].current,
                            INIT_VLC_DEFAULT_SIZES(h[i].lengths),
-                    h[i].bits, sizeof(uint32_t), sizeof(uint32_t), INIT_VLC_LE);
+                                     INIT_VLC_DEFAULT_SIZES(h[i].bits),
+                                     INIT_VLC_DEFAULT_SIZES(h[i].values),
+                                     INIT_VLC_LE);
             if (ret < 0) {
                 av_log(avctx, AV_LOG_ERROR, "Cannot build VLC table\n");
                 goto error;
             }
-        }
+        } else
+            values[i] = h[i].values[0];
     }
     /* this codec relies on wraparound instead of clipping audio */
     if(bits) { //decode 16-bit data
@@ -694,26 +700,26 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data,
                 if(vlc[2].table)
                     res = get_vlc2(&gb, vlc[2].table, SMKTREE_BITS, 3);
                 else
-                    res = 0;
-                val  = h[2].values[res];
+                    res = values[2];
+                val  = res;
                 if(vlc[3].table)
                     res = get_vlc2(&gb, vlc[3].table, SMKTREE_BITS, 3);
                 else
-                    res = 0;
-                val |= h[3].values[res] << 8;
+                    res = values[3];
+                val |= res << 8;
                 pred[1] += (unsigned)sign_extend(val, 16);
                 *samples++ = pred[1];
             } else {
                 if(vlc[0].table)
                     res = get_vlc2(&gb, vlc[0].table, SMKTREE_BITS, 3);
                 else
-                    res = 0;
-                val  = h[0].values[res];
+                    res = values[0];
+                val  = res;
                 if(vlc[1].table)
                     res = get_vlc2(&gb, vlc[1].table, SMKTREE_BITS, 3);
                 else
-                    res = 0;
-                val |= h[1].values[res] << 8;
+                    res = values[1];
+                val |= res << 8;
                 pred[0] += (unsigned)sign_extend(val, 16);
                 *samples++ = pred[0];
             }
@@ -732,15 +738,15 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data,
                 if(vlc[1].table)
                     res = get_vlc2(&gb, vlc[1].table, SMKTREE_BITS, 3);
                 else
-                    res = 0;
-                pred[1] += sign_extend(h[1].values[res], 8);
+                    res = values[1];
+                pred[1] += sign_extend(res, 8);
                 *samples8++ = pred[1];
             } else {
                 if(vlc[0].table)
                     res = get_vlc2(&gb, vlc[0].table, SMKTREE_BITS, 3);
                 else
-                    res = 0;
-                pred[0] += sign_extend(h[0].values[res], 8);
+                    res = values[0];
+                pred[0] += sign_extend(res, 8);
                 *samples8++ = pred[0];
             }
         }