Simplify address arithmetic in vp9_optimize_b

Simplify address arithmetic on token_costs to reduce the number of generated
instructions that are used for address arithmetic inside routine
vp9_optimize_b. It also helps improve instruction scheduling depending on
compiler and optimization level.

Measured a 9.3% reduction in retired instructions and 5.3% reduction in
execution time for this routine with GCC v4.8.4 and optimization flags -O3,
and a reduction of up to 11.6% in execution time with other compilers.

No change in behavior.

TEST=Verified that encoded files match bit for bit, with and without this
change.
BUG=b/33678225

Change-Id: I6098650fb5cd2aa04e014fe6e68ca20761f3a21f

1 files changed, 10 insertions, 14 deletions

diff --git a/vp9/encoder/vp9_encodemb.c b/vp9/encoder/vp9_encodemb.c
index 20ebe6819..c88efa526 100644
--- a/vp9/encoder/vp9_encodemb.c
+++ b/vp9/encoder/vp9_encodemb.c
@@ -109,6 +109,8 @@ int vp9_optimize_b(MACROBLOCK *mb, int plane, int block, TX_SIZE tx_size,
   int64_t error0, error1;
   int16_t t0, t1;
   EXTRABIT e0;
+  unsigned int(*const token_costs)[2][COEFF_CONTEXTS][ENTROPY_TOKENS] =
+      mb->token_costs[tx_size][type][ref];
   int best, band, pt, i, final_eob;
 #if CONFIG_VP9_HIGHBITDEPTH
   const int *cat6_high_cost = vp9_get_high_cost_table(xd->bd);
@@ -148,10 +150,8 @@ int vp9_optimize_b(MACROBLOCK *mb, int plane, int block, TX_SIZE tx_size,
       if (next < default_eob) {
         band = band_translate[i + 1];
         pt = trellis_get_coeff_context(scan, nb, i, t0, token_cache);
-        rate0 += mb->token_costs[tx_size][type][ref][band][0][pt]
-                                [tokens[next][0].token];
-        rate1 += mb->token_costs[tx_size][type][ref][band][0][pt]
-                                [tokens[next][1].token];
+        rate0 += token_costs[band][0][pt][tokens[next][0].token];
+        rate1 += token_costs[band][0][pt][tokens[next][1].token];
       }
       UPDATE_RD_COST();
       /* And pick the best. */
@@ -208,13 +208,11 @@ int vp9_optimize_b(MACROBLOCK *mb, int plane, int block, TX_SIZE tx_size,
         band = band_translate[i + 1];
         if (t0 != EOB_TOKEN) {
           pt = trellis_get_coeff_context(scan, nb, i, t0, token_cache);
-          rate0 += mb->token_costs[tx_size][type][ref][band][!x][pt]
-                                  [tokens[next][0].token];
+          rate0 += token_costs[band][!x][pt][tokens[next][0].token];
         }
         if (t1 != EOB_TOKEN) {
           pt = trellis_get_coeff_context(scan, nb, i, t1, token_cache);
-          rate1 += mb->token_costs[tx_size][type][ref][band][!x][pt]
-                                  [tokens[next][1].token];
+          rate1 += token_costs[band][!x][pt][tokens[next][1].token];
         }
       }
 
@@ -270,13 +268,11 @@ int vp9_optimize_b(MACROBLOCK *mb, int plane, int block, TX_SIZE tx_size,
       t1 = tokens[next][1].token;
       /* Update the cost of each path if we're past the EOB token. */
       if (t0 != EOB_TOKEN) {
-        tokens[next][0].rate +=
-            mb->token_costs[tx_size][type][ref][band][1][pt][t0];
+        tokens[next][0].rate += token_costs[band][1][pt][t0];
         tokens[next][0].token = ZERO_TOKEN;
       }
       if (t1 != EOB_TOKEN) {
-        tokens[next][1].rate +=
-            mb->token_costs[tx_size][type][ref][band][1][pt][t1];
+        tokens[next][1].rate += token_costs[band][1][pt][t1];
         tokens[next][1].token = ZERO_TOKEN;
       }
       tokens[i][0].best_index = tokens[i][1].best_index = 0;
@@ -292,8 +288,8 @@ int vp9_optimize_b(MACROBLOCK *mb, int plane, int block, TX_SIZE tx_size,
   error1 = tokens[next][1].error;
   t0 = tokens[next][0].token;
   t1 = tokens[next][1].token;
-  rate0 += mb->token_costs[tx_size][type][ref][band][0][ctx][t0];
-  rate1 += mb->token_costs[tx_size][type][ref][band][0][ctx][t1];
+  rate0 += token_costs[band][0][ctx][t0];
+  rate1 += token_costs[band][0][ctx][t1];
   UPDATE_RD_COST();
   best = rd_cost1 < rd_cost0;
   final_eob = -1;