Refactor build_prediction_by_left_pred

Reduce data dependency in OBMC prediction.

Change-Id: I862184366972b8c1323832df4c72818dc84204b8

av1/encoder/reconinter_enc.c

diff --git a/av1/encoder/reconinter_enc.c b/av1/encoder/reconinter_enc.c
index 545d30b..e1d5eb8 100644
--- a/av1/encoder/reconinter_enc.c
+++ b/av1/encoder/reconinter_enc.c
@@ -416,6 +416,8 @@
   mi_y = left_mi_row << MI_SIZE_LOG2;
   const BLOCK_SIZE bsize = xd->mi[0]->sb_type;
 
+  InterPredParams inter_pred_params;
+
   for (int j = 0; j < num_planes; ++j) {
     const struct macroblockd_plane *pd = &xd->plane[j];
     int bw = clamp(block_size_wide[bsize] >> (pd->subsampling_x + 1), 4,
@@ -423,8 +425,19 @@
     int bh = (left_mi_height << MI_SIZE_LOG2) >> pd->subsampling_y;
 
     if (av1_skip_u4x4_pred_in_obmc(bsize, pd, 1)) continue;
-    build_inter_predictors(ctxt->cm, xd, j, &backup_mbmi, 1, bw, bh, mi_x,
-                           mi_y);
+
+    const struct buf_2d *const pre_buf = &pd->pre[0];
+    const MV mv = backup_mbmi.mv[0].as_mv;
+
+    av1_init_inter_params(&inter_pred_params, bw, bh, mi_y, mi_x,
+                          pd->subsampling_x, pd->subsampling_y, xd->bd,
+                          is_cur_buf_hbd(xd), 0, xd->block_ref_scale_factors[0],
+                          pre_buf, backup_mbmi.interp_filters);
+    inter_pred_params.conv_params = get_conv_params(0, 0, xd->bd);
+
+    av1_build_inter_predictor(pre_buf->buf, pre_buf->stride, pd->dst.buf,
+                              pd->dst.stride, &mv, mi_x, mi_y,
+                              &inter_pred_params);
   }
 }