Remove redundant transform size selection stage

This improves the encoding speed. For bus at CIF 1000 kbps, the
encoding time (speed 0) goes down from 248000 ms to 231000 ms,
i.e., 7% speed-up.

Change-Id: Ic59b39b7eb1b6e72fdb646e22bfeddd3eff1cb71

av1/encoder/rdopt.c

@@ -648,13 +648,15 @@ static void choose_tx_size_from_rd(AV1_COMP *cpi, MACROBLOCK *x, int *rate,
   int n, m;
   int s0, s1;
   int64_t best_rd = INT64_MAX, last_rd = INT64_MAX;
-  TX_SIZE best_tx = max_tx_size;
+  TX_SIZE best_tx = TX_SIZES;
   int start_tx, end_tx;
   const int tx_select = cm->tx_mode == TX_MODE_SELECT;
   TX_TYPE tx_type, best_tx_type = DCT_DCT;
   const int is_inter = is_inter_block(mbmi);
-
+  uint8_t zcoeff_blk[TX_SIZES][256];
+  int num_4x4_blks = 1 << (num_pels_log2_lookup[bs] - 4);
   const aom_prob *tx_probs = get_tx_probs2(max_tx_size, xd, &cm->fc->tx_probs);
+
   assert(skip_prob > 0);
   s0 = av1_cost_bit(skip_prob, 0);
   s1 = av1_cost_bit(skip_prob, 1);
@@ -738,15 +740,18 @@ static void choose_tx_size_from_rd(AV1_COMP *cpi, MACROBLOCK *x, int *rate,
         *skip = s;
         *psse = sse;
         best_tx_type = mbmi->tx_type;
+        memcpy(zcoeff_blk, x->zcoeff_blk[n], num_4x4_blks);
       }
     }
   }
 
   mbmi->tx_size = best_tx;
   mbmi->tx_type = best_tx_type;
+
   if (mbmi->tx_size >= TX_32X32) assert(mbmi->tx_type == DCT_DCT);
-  txfm_rd_in_plane(x, &r, &d, &s, &sse, ref_best_rd, 0, bs, best_tx,
-                   cpi->sf.use_fast_coef_costing);
+
+  if (best_tx < TX_SIZES)
+    memcpy(x->zcoeff_blk[best_tx], zcoeff_blk, num_4x4_blks);
 }
 
 static void super_block_yrd(AV1_COMP *cpi, MACROBLOCK *x, int *rate,
@@ -4016,6 +4021,7 @@ void av1_rd_pick_inter_mode_sb(AV1_COMP *cpi, TileDataEnc *tile_data,
       }
 #endif  // CONFIG_EXT_INTRA
       distortion2 = distortion_y + distortion_uv;
+      av1_encode_intra_block_plane(x, bsize, 0);
     } else {
 #if CONFIG_REF_MV
       int_mv backup_ref_mv[2];