Totally remove prev_mi in VP9 decoder.

This will save the memory and improve the decode speed due to
removing unnecessary memset of big prev_mi array for
all the key frames.

Decoding a all key frames 1080p video shows speed improve around 2%.

Change-Id: I6284a445c1291056e3c15135c3c20d502f791c10

4 files changed, 13 insertions, 82 deletions

diff --git a/vp9/common/vp9_alloccommon.c b/vp9/common/vp9_alloccommon.c
index 8a41f07f8..03959e365 100644
--- a/vp9/common/vp9_alloccommon.c
+++ b/vp9/common/vp9_alloccommon.c
@@ -17,17 +17,6 @@
 #include "vp9/common/vp9_onyxc_int.h"
 #include "vp9/common/vp9_systemdependent.h"
 
-static void clear_mi_border(const VP9_COMMON *cm, MODE_INFO *mi) {
-  int i;
-
-  // Top border row
-  vpx_memset(mi, 0, sizeof(*mi) * cm->mi_stride);
-
-  // Left border column
-  for (i = 1; i < cm->mi_rows + 1; ++i)
-    vpx_memset(&mi[i * cm->mi_stride], 0, sizeof(*mi));
-}
-
 void vp9_set_mb_mi(VP9_COMMON *cm, int width, int height) {
   const int aligned_width = ALIGN_POWER_OF_TWO(width, MI_SIZE_LOG2);
   const int aligned_height = ALIGN_POWER_OF_TWO(height, MI_SIZE_LOG2);
@@ -41,48 +30,6 @@ void vp9_set_mb_mi(VP9_COMMON *cm, int width, int height) {
   cm->MBs = cm->mb_rows * cm->mb_cols;
 }
 
-static void setup_mi(VP9_COMMON *cm) {
-  cm->mi = cm->mip + cm->mi_stride + 1;
-  cm->prev_mi = cm->prev_mip + cm->mi_stride + 1;
-
-  vpx_memset(cm->mip, 0, cm->mi_stride * (cm->mi_rows + 1) * sizeof(*cm->mip));
-  clear_mi_border(cm, cm->prev_mip);
-}
-
-static int alloc_mi(VP9_COMMON *cm, int mi_size) {
-  int i;
-
-  for (i = 0; i < 2; ++i) {
-    cm->mip_array[i] =
-        (MODE_INFO *)vpx_calloc(mi_size, sizeof(MODE_INFO));
-    if (cm->mip_array[i] == NULL)
-      return 1;
-  }
-
-  cm->mi_alloc_size = mi_size;
-
-  // Init the index.
-  cm->mi_idx = 0;
-  cm->prev_mi_idx = 1;
-
-  cm->mip = cm->mip_array[cm->mi_idx];
-  cm->prev_mip = cm->mip_array[cm->prev_mi_idx];
-
-  return 0;
-}
-
-static void free_mi(VP9_COMMON *cm) {
-  int i;
-
-  for (i = 0; i < 2; ++i) {
-    vpx_free(cm->mip_array[i]);
-    cm->mip_array[i] = NULL;
-  }
-
-  cm->mip = NULL;
-  cm->prev_mip = NULL;
-}
-
 void vp9_free_ref_frame_buffers(VP9_COMMON *cm) {
   int i;
 
@@ -101,14 +48,11 @@ void vp9_free_ref_frame_buffers(VP9_COMMON *cm) {
 }
 
 void vp9_free_context_buffers(VP9_COMMON *cm) {
-  free_mi(cm);
-
+  cm->free_mi(cm);
   vpx_free(cm->last_frame_seg_map);
   cm->last_frame_seg_map = NULL;
-
   vpx_free(cm->above_context);
   cm->above_context = NULL;
-
   vpx_free(cm->above_seg_context);
   cm->above_seg_context = NULL;
 }
@@ -117,7 +61,7 @@ int vp9_alloc_context_buffers(VP9_COMMON *cm, int width, int height) {
   vp9_free_context_buffers(cm);
 
   vp9_set_mb_mi(cm, width, height);
-  if (alloc_mi(cm, cm->mi_stride * calc_mi_size(cm->mi_rows)))
+  if (cm->alloc_mi(cm, cm->mi_stride * calc_mi_size(cm->mi_rows)))
     goto fail;
 
   cm->last_frame_seg_map = (uint8_t *)vpx_calloc(cm->mi_rows * cm->mi_cols, 1);
@@ -204,22 +148,7 @@ void vp9_remove_common(VP9_COMMON *cm) {
 }
 
 void vp9_init_context_buffers(VP9_COMMON *cm) {
-  setup_mi(cm);
+  cm->setup_mi(cm);
   if (cm->last_frame_seg_map)
     vpx_memset(cm->last_frame_seg_map, 0, cm->mi_rows * cm->mi_cols);
 }
-
-void vp9_swap_mi_and_prev_mi(VP9_COMMON *cm) {
-  // Swap indices.
-  const int tmp = cm->mi_idx;
-  cm->mi_idx = cm->prev_mi_idx;
-  cm->prev_mi_idx = tmp;
-
-  // Current mip will be the prev_mip for the next frame.
-  cm->mip = cm->mip_array[cm->mi_idx];
-  cm->prev_mip = cm->mip_array[cm->prev_mi_idx];
-
-  // Update the upper left visible macroblock ptrs.
-  cm->mi = cm->mip + cm->mi_stride + 1;
-  cm->prev_mi = cm->prev_mip + cm->mi_stride + 1;
-}
diff --git a/vp9/common/vp9_alloccommon.h b/vp9/common/vp9_alloccommon.h
index c5b893fac..955bb9ec5 100644
--- a/vp9/common/vp9_alloccommon.h
+++ b/vp9/common/vp9_alloccommon.h
@@ -31,7 +31,6 @@ int vp9_alloc_state_buffers(struct VP9Common *cm, int width, int height);
 void vp9_free_state_buffers(struct VP9Common *cm);
 
 void vp9_set_mb_mi(struct VP9Common *cm, int width, int height);
-void vp9_swap_mi_and_prev_mi(struct VP9Common *cm);
 
 #ifdef __cplusplus
 }  // extern "C"
diff --git a/vp9/common/vp9_entropymode.c b/vp9/common/vp9_entropymode.c
index 1a24572ba..d7610ed28 100644
--- a/vp9/common/vp9_entropymode.c
+++ b/vp9/common/vp9_entropymode.c
@@ -464,7 +464,8 @@ void vp9_setup_past_independence(VP9_COMMON *cm) {
     cm->frame_contexts[cm->frame_context_idx] = *cm->fc;
   }
 
-  if (frame_is_intra_only(cm))
+  // prev_mip will only be allocated in encoder.
+  if (frame_is_intra_only(cm) && cm->prev_mip)
     vpx_memset(cm->prev_mip, 0, cm->mi_stride * (cm->mi_rows + 1) *
                                     sizeof(*cm->prev_mip));
 
diff --git a/vp9/common/vp9_onyxc_int.h b/vp9/common/vp9_onyxc_int.h
index b3a6590b2..ae69c0c00 100644
--- a/vp9/common/vp9_onyxc_int.h
+++ b/vp9/common/vp9_onyxc_int.h
@@ -96,7 +96,6 @@ typedef struct VP9Common {
 #endif
 
   YV12_BUFFER_CONFIG *frame_to_show;
-
   RefCntBuffer frame_bufs[FRAME_BUFFERS];
   RefCntBuffer *prev_frame;
 
@@ -149,17 +148,20 @@ typedef struct VP9Common {
 
   /* We allocate a MODE_INFO struct for each macroblock, together with
      an extra row on top and column on the left to simplify prediction. */
-
-  int mi_idx;
-  int prev_mi_idx;
   int mi_alloc_size;
-  MODE_INFO *mip_array[2];
-
   MODE_INFO *mip; /* Base of allocated array */
   MODE_INFO *mi;  /* Corresponds to upper left visible macroblock */
+
+  // TODO(agrange): Move prev_mi into encoder structure.
+  // prev_mip and prev_mi will only be allocated in VP9 encoder.
   MODE_INFO *prev_mip; /* MODE_INFO array 'mip' from last decoded frame */
   MODE_INFO *prev_mi;  /* 'mi' from last frame (points into prev_mip) */
 
+  // Separate mi functions between encoder and decoder.
+  int (*alloc_mi)(struct VP9Common *cm, int mi_size);
+  void (*free_mi)(struct VP9Common *cm);
+  void (*setup_mi)(struct VP9Common *cm);
+
 
   // Whether to use previous frame's motion vectors for prediction.
   int use_prev_frame_mvs;