Simplify redundant code related to prev_frame mvs

For the setup of prev_frame and use_prev_frame_mvs, the removed
code has a copy that already exists inside read_uncompressed_header().

Change-Id: Ic814bc1f1781320e13f9ac3e183f21e2cab589d8

av1/decoder/decodeframe.c

@@ -3239,9 +3239,6 @@ size_t av1_decode_frame_headers_and_setup(AV1Decoder *pbi, const uint8_t *data,
                                           const uint8_t **p_data_end) {
   AV1_COMMON *const cm = &pbi->common;
   MACROBLOCKD *const xd = &pbi->mb;
-#if !CONFIG_TEMPMV_SIGNALING
-  RefBuffer *last_fb_ref_buf = &cm->frame_refs[LAST_FRAME - LAST_FRAME];
-#endif
 
 #if CONFIG_BITSTREAM_DEBUG
   bitstream_queue_set_frame_read(cm->current_video_frame * 2 + cm->show_frame);
@@ -3313,43 +3310,6 @@ size_t av1_decode_frame_headers_and_setup(AV1Decoder *pbi, const uint8_t *data,
 
   cm->setup_mi(cm);
 
-#if !CONFIG_TEMPMV_SIGNALING
-  // NOTE(zoeliu): As cm->prev_frame can take neither a frame of
-  //               show_exisiting_frame=1, nor can it take a frame not used as
-  //               a reference, it is probable that by the time it is being
-  //               referred to, the frame buffer it originally points to may
-  //               already get expired and have been reassigned to the current
-  //               newly coded frame. Hence, we need to check whether this is
-  //               the case, and if yes, we have 2 choices:
-  //               (1) Simply disable the use of previous frame mvs; or
-  //               (2) Have cm->prev_frame point to one reference frame buffer,
-  //                   e.g. LAST_FRAME.
-  if (!dec_is_ref_frame_buf(pbi, cm->prev_frame)) {
-    // Reassign the LAST_FRAME buffer to cm->prev_frame.
-    cm->prev_frame = last_fb_ref_buf->idx != INVALID_IDX
-                         ? &cm->buffer_pool->frame_bufs[last_fb_ref_buf->idx]
-                         : NULL;
-  }
-#endif
-
-#if CONFIG_TEMPMV_SIGNALING
-  if (cm->use_prev_frame_mvs && !frame_can_use_prev_frame_mvs(cm)) {
-    aom_internal_error(&cm->error, AOM_CODEC_CORRUPT_FRAME,
-                       "Frame wrongly requests previous frame MVs");
-  }
-#else
-  cm->use_prev_frame_mvs = !cm->error_resilient_mode && cm->prev_frame &&
-#if CONFIG_HORZONLY_FRAME_SUPERRES
-                           cm->width == cm->last_width &&
-                           cm->height == cm->last_height &&
-#else
-                           cm->width == cm->prev_frame->buf.y_crop_width &&
-                           cm->height == cm->prev_frame->buf.y_crop_height &&
-#endif  // CONFIG_HORZONLY_FRAME_SUPERRES
-                           !cm->last_intra_only && cm->last_show_frame &&
-                           (cm->last_frame_type != KEY_FRAME);
-#endif  // CONFIG_TEMPMV_SIGNALING
-
 #if CONFIG_SEGMENT_PRED_LAST
   cm->current_frame_seg_map = cm->cur_frame->seg_map;
   if (cm->current_frame_seg_map)