decodemv.c: remove unused argument

Also, make some locals 'const'.

Change-Id: I030c493b8bb7a1827df16a9feda38dd9dd1e424c

av1/decoder/decodemv.c

@@ -284,14 +284,13 @@ static void read_drl_idx(FRAME_CONTEXT *ec_ctx, MACROBLOCKD *xd,
 }
 
 #if CONFIG_EXT_WARPED_MOTION
-static MOTION_MODE read_motion_mode(AV1_COMMON *cm, MACROBLOCKD *xd,
-                                    MODE_INFO *mi, aom_reader *r, int best) {
+static MOTION_MODE read_motion_mode(MACROBLOCKD *xd, MODE_INFO *mi,
+                                    aom_reader *r, int best) {
 #else
-static MOTION_MODE read_motion_mode(AV1_COMMON *cm, MACROBLOCKD *xd,
-                                    MODE_INFO *mi, aom_reader *r) {
+static MOTION_MODE read_motion_mode(MACROBLOCKD *xd, MODE_INFO *mi,
+                                    aom_reader *r) {
 #endif  // CONFIG_EXT_WARPED_MOTION
   MB_MODE_INFO *mbmi = &mi->mbmi;
-  (void)cm;
 
 #if CONFIG_EXT_SKIP
   if (mbmi->skip_mode) return SIMPLE_TRANSLATION;
@@ -1297,9 +1296,8 @@ static int read_mv_component(aom_reader *r, nmv_component *mvcomp,
 
 static INLINE void read_mv(aom_reader *r, MV *mv, const MV *ref,
                            nmv_context *ctx, MvSubpelPrecision precision) {
-  MV_JOINT_TYPE joint_type;
   MV diff = { 0, 0 };
-  joint_type =
+  const MV_JOINT_TYPE joint_type =
       (MV_JOINT_TYPE)aom_read_symbol(r, ctx->joints_cdf, MV_JOINTS, ACCT_STR);
 
   if (mv_joint_vertical(joint_type))
@@ -1345,14 +1343,12 @@ static REFERENCE_MODE read_block_reference_mode(AV1_COMMON *cm,
   aom_read_symbol(r, av1_get_pred_cdf_##pname(xd), 2, ACCT_STR)
 
 #if CONFIG_EXT_COMP_REFS
-static COMP_REFERENCE_TYPE read_comp_reference_type(AV1_COMMON *cm,
-                                                    const MACROBLOCKD *xd,
+static COMP_REFERENCE_TYPE read_comp_reference_type(const MACROBLOCKD *xd,
                                                     aom_reader *r) {
   const int ctx = av1_get_comp_reference_type_context(xd);
-  COMP_REFERENCE_TYPE comp_ref_type;
-  (void)cm;
-  comp_ref_type = (COMP_REFERENCE_TYPE)aom_read_symbol(
-      r, xd->tile_ctx->comp_ref_type_cdf[ctx], 2, ACCT_STR);
+  const COMP_REFERENCE_TYPE comp_ref_type =
+      (COMP_REFERENCE_TYPE)aom_read_symbol(
+          r, xd->tile_ctx->comp_ref_type_cdf[ctx], 2, ACCT_STR);
   FRAME_COUNTS *counts = xd->counts;
   if (counts) ++counts->comp_ref_type[ctx][comp_ref_type];
   return comp_ref_type;  // UNIDIR_COMP_REFERENCE or BIDIR_COMP_REFERENCE
@@ -1400,8 +1396,7 @@ static void read_ref_frames(AV1_COMMON *const cm, MACROBLOCKD *const xd,
     // FIXME(rbultje) I'm pretty sure this breaks segmentation ref frame coding
     if (mode == COMPOUND_REFERENCE) {
 #if CONFIG_EXT_COMP_REFS
-      const COMP_REFERENCE_TYPE comp_ref_type =
-          read_comp_reference_type(cm, xd, r);
+      const COMP_REFERENCE_TYPE comp_ref_type = read_comp_reference_type(xd, r);
 
       if (comp_ref_type == UNIDIR_COMP_REFERENCE) {
         const int ctx = av1_get_pred_context_uni_comp_ref_p(xd);
@@ -2223,9 +2218,9 @@ static void read_inter_block_mode_info(AV1Decoder *const pbi,
 
   if (mbmi->ref_frame[1] != INTRA_FRAME)
 #if CONFIG_EXT_WARPED_MOTION
-    mbmi->motion_mode = read_motion_mode(cm, xd, mi, r, best_cand);
+    mbmi->motion_mode = read_motion_mode(xd, mi, r, best_cand);
 #else
-    mbmi->motion_mode = read_motion_mode(cm, xd, mi, r);
+    mbmi->motion_mode = read_motion_mode(xd, mi, r);
 #endif  // CONFIG_EXT_WARPED_MOTION
 
 #if CONFIG_JNT_COMP