Remove an unused variable arf_map

arf_map was used to store all the ALTREFs' virtual indices,
but now we use ref_fb_idx to store all reference frames'
virtual indices. Therefore this arf_map is no longer needed and
can be removed.

Change-Id: I8fca3ae43ca868db73ce6f4e7a5595e360b0d08d

av1/encoder/encoder.c

diff --git a/av1/encoder/encoder.c b/av1/encoder/encoder.c
index 7ff0fb0..c3d61de 100644
--- a/av1/encoder/encoder.c
+++ b/av1/encoder/encoder.c
@@ -847,8 +847,6 @@
   int fb_idx;
   for (fb_idx = 0; fb_idx < REF_FRAMES; ++fb_idx)
     cpi->ref_fb_idx[fb_idx] = fb_idx;
-  for (fb_idx = 0; fb_idx < MAX_EXT_ARFS + 1; ++fb_idx)
-    cpi->arf_map[fb_idx] = LAST_REF_FRAMES + 2 + fb_idx;
   cpi->rate_index = 0;
   cpi->rate_size = 0;
   cpi->cur_poc = -1;
@@ -3373,25 +3371,22 @@
     cpi->ref_fb_idx[ALTREF_FRAME - 1] = cpi->ref_fb_idx[GOLDEN_FRAME - 1];
     cpi->ref_fb_idx[GOLDEN_FRAME - 1] = tmp;
 
-    // We need to modify the mapping accordingly
-    cpi->arf_map[0] = cpi->ref_fb_idx[ALTREF_FRAME - 1];
     // TODO(zoeliu): Do we need to copy cpi->interp_filter_selected[0] over to
     // cpi->interp_filter_selected[GOLDEN_FRAME]?
   } else if (cpi->rc.is_src_frame_ext_arf && cm->show_existing_frame) {
+#if CONFIG_DEBUG
+    const GF_GROUP *const gf_group = &cpi->twopass.gf_group;
+    assert(gf_group->update_type[gf_group->index] == INTNL_OVERLAY_UPDATE);
+#endif
     // Deal with the special case for showing existing internal ALTREF_FRAME
     // Refresh the LAST_FRAME with the ALTREF_FRAME and retire the LAST3_FRAME
     // by updating the virtual indices.
-    const GF_GROUP *const gf_group = &cpi->twopass.gf_group;
-    const int which_arf = gf_group->arf_ref_idx[gf_group->index];
-    assert(gf_group->update_type[gf_group->index] == INTNL_OVERLAY_UPDATE);
 
     const int tmp = cpi->ref_fb_idx[LAST_REF_FRAMES - 1];
     shift_last_ref_frames(cpi);
 
     cpi->ref_fb_idx[LAST_FRAME - 1] = cpi->ref_fb_idx[ALTREF2_FRAME - 1];
     cpi->ref_fb_idx[ALTREF2_FRAME - 1] = tmp;
-    // We need to modify the mapping accordingly
-    cpi->arf_map[which_arf] = cpi->ref_fb_idx[ALTREF2_FRAME - 1];
 
     memcpy(cpi->interp_filter_selected[LAST_FRAME],
            cpi->interp_filter_selected[ALTREF2_FRAME],

av1/encoder/encoder.h

diff --git a/av1/encoder/encoder.h b/av1/encoder/encoder.h
index 1450efc..0ddb4f1 100644
--- a/av1/encoder/encoder.h
+++ b/av1/encoder/encoder.h
@@ -667,7 +667,6 @@
   int existing_fb_idx_to_show;
   int is_arf_filter_off[MAX_EXT_ARFS + 1];
   int num_extra_arfs;
-  int arf_map[MAX_EXT_ARFS + 1];
   int arf_pos_in_gf[MAX_EXT_ARFS + 1];
   int arf_pos_for_ovrly[MAX_EXT_ARFS + 1];
   int global_motion_search_done;