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vp9 com/dec: avoid reading unavailable above/left

in most cases at least the left column was a harmless race as it was
left unused later in the code.

Change-Id: I43211df66fb157c6feecf08c681add4fcf18b644

--- a/vp9/common/vp9_pred_common.c

+++ b/vp9/common/vp9_pred_common.c

@@ -16,12 +16,20 @@

 #include "vp9/common/vp9_seg_common.h"

 #include "vp9/common/vp9_treecoder.h"

+static INLINE const MB_MODE_INFO *get_above_mbmi(const MODE_INFO *const above) {

+  return (above != NULL) ? &above->mbmi : NULL;

+}

+

+static INLINE const MB_MODE_INFO *get_left_mbmi(const MODE_INFO *const left) {

+  return (left != NULL) ? &left->mbmi : NULL;

+}

+

 // Returns a context number for the given MB prediction signal

 unsigned char vp9_get_pred_context_switchable_interp(const MACROBLOCKD *xd) {

-  const MODE_INFO * const above_mi = xd->mi_8x8[-xd->mode_info_stride];

-  const MODE_INFO * const left_mi = xd->mi_8x8[-1];

-  const int left_in_image = xd->left_available && left_mi;

-  const int above_in_image = xd->up_available && above_mi;

+  const MODE_INFO *const above_mi = get_above_mi(xd);

+  const MODE_INFO *const left_mi = get_left_mi(xd);

+  const int above_in_image = above_mi != NULL;

+  const int left_in_image = left_mi != NULL;

   // Note:

   // The mode info data structure has a one element border above and to the

   // left of the entries correpsonding to real macroblocks.

@@ -53,14 +61,14 @@

 }

 // Returns a context number for the given MB prediction signal

 unsigned char vp9_get_pred_context_intra_inter(const MACROBLOCKD *xd) {

-  const MODE_INFO * const above_mi = xd->mi_8x8[-xd->mode_info_stride];

-  const MODE_INFO * const left_mi = xd->mi_8x8[-1];

-  const MB_MODE_INFO *const above_mbmi = above_mi ? &above_mi->mbmi : 0;

-  const MB_MODE_INFO *const left_mbmi = left_mi ? &left_mi->mbmi : 0;

-  const int left_in_image = xd->left_available && left_mi;

-  const int above_in_image = xd->up_available && above_mi;

-  const int left_intra = left_in_image ? !is_inter_block(left_mbmi) : 1;

+  const MODE_INFO *const above_mi = get_above_mi(xd);

+  const MODE_INFO *const left_mi = get_left_mi(xd);

+  const MB_MODE_INFO *const above_mbmi = get_above_mbmi(above_mi);

+  const MB_MODE_INFO *const left_mbmi = get_left_mbmi(left_mi);

+  const int above_in_image = above_mi != NULL;

+  const int left_in_image = left_mi != NULL;

   const int above_intra = above_in_image ? !is_inter_block(above_mbmi) : 1;

+  const int left_intra = left_in_image ? !is_inter_block(left_mbmi) : 1;

   // The mode info data structure has a one element border above and to the

   // left of the entries corresponding to real macroblocks.

@@ -81,12 +89,12 @@

 unsigned char vp9_get_pred_context_comp_inter_inter(const VP9_COMMON *cm,

                                                     const MACROBLOCKD *xd) {

   int pred_context;

-  const MODE_INFO * const above_mi = xd->mi_8x8[-xd->mode_info_stride];

-  const MODE_INFO * const left_mi = xd->mi_8x8[-1];

-  const MB_MODE_INFO *const above_mbmi = above_mi ? &above_mi->mbmi : 0;

-  const MB_MODE_INFO *const left_mbmi = left_mi ? &left_mi->mbmi : 0;

-  const int left_in_image = xd->left_available && left_mi;

-  const int above_in_image = xd->up_available && above_mi;

+  const MODE_INFO *const above_mi = get_above_mi(xd);

+  const MODE_INFO *const left_mi = get_left_mi(xd);

+  const MB_MODE_INFO *const above_mbmi = get_above_mbmi(above_mi);

+  const MB_MODE_INFO *const left_mbmi = get_left_mbmi(left_mi);

+  const int above_in_image = above_mi != NULL;

+  const int left_in_image = left_mi != NULL;

   // Note:

   // The mode info data structure has a one element border above and to the

   // left of the entries correpsonding to real macroblocks.

@@ -126,14 +134,14 @@

 unsigned char vp9_get_pred_context_comp_ref_p(const VP9_COMMON *cm,

                                               const MACROBLOCKD *xd) {

   int pred_context;

-  const MODE_INFO * const above_mi = xd->mi_8x8[-cm->mode_info_stride];

-  const MODE_INFO * const left_mi = xd->mi_8x8[-1];

-  const MB_MODE_INFO *const above_mbmi = above_mi ? &above_mi->mbmi : 0;

-  const MB_MODE_INFO *const left_mbmi = left_mi ? &left_mi->mbmi : 0;

-  const int left_in_image = xd->left_available && left_mi;

-  const int above_in_image = xd->up_available && above_mi;

-  const int left_intra = left_in_image ? !is_inter_block(left_mbmi) : 1;

+  const MODE_INFO *const above_mi = get_above_mi(xd);

+  const MODE_INFO *const left_mi = get_left_mi(xd);

+  const MB_MODE_INFO *const above_mbmi = get_above_mbmi(above_mi);

+  const MB_MODE_INFO *const left_mbmi = get_left_mbmi(left_mi);

+  const int above_in_image = above_mi != NULL;

+  const int left_in_image = left_mi != NULL;

   const int above_intra = above_in_image ? !is_inter_block(above_mbmi) : 1;

+  const int left_intra = left_in_image ? !is_inter_block(left_mbmi) : 1;

   // Note:

   // The mode info data structure has a one element border above and to the

   // left of the entries correpsonding to real macroblocks.

@@ -206,14 +214,14 @@

 }

 unsigned char vp9_get_pred_context_single_ref_p1(const MACROBLOCKD *xd) {

   int pred_context;

-  const MODE_INFO * const above_mi = xd->mi_8x8[-xd->mode_info_stride];

-  const MODE_INFO * const left_mi = xd->mi_8x8[-1];

-  const MB_MODE_INFO *const above_mbmi = above_mi ? &above_mi->mbmi : 0;

-  const MB_MODE_INFO *const left_mbmi = left_mi ? &left_mi->mbmi : 0;

-  const int left_in_image = xd->left_available && left_mi;

-  const int above_in_image = xd->up_available && above_mi;

-  const int left_intra = left_in_image ? !is_inter_block(left_mbmi) : 1;

+  const MODE_INFO *const above_mi = get_above_mi(xd);

+  const MODE_INFO *const left_mi = get_left_mi(xd);

+  const MB_MODE_INFO *const above_mbmi = get_above_mbmi(above_mi);

+  const MB_MODE_INFO *const left_mbmi = get_left_mbmi(left_mi);

+  const int above_in_image = above_mi != NULL;

+  const int left_in_image = left_mi != NULL;

   const int above_intra = above_in_image ? !is_inter_block(above_mbmi) : 1;

+  const int left_intra = left_in_image ? !is_inter_block(left_mbmi) : 1;

   // Note:

   // The mode info data structure has a one element border above and to the

   // left of the entries correpsonding to real macroblocks.

@@ -272,14 +280,14 @@

 unsigned char vp9_get_pred_context_single_ref_p2(const MACROBLOCKD *xd) {

   int pred_context;

-  const MODE_INFO * const above_mi = xd->mi_8x8[-xd->mode_info_stride];

-  const MODE_INFO * const left_mi = xd->mi_8x8[-1];

-  const MB_MODE_INFO *const above_mbmi = above_mi ? &above_mi->mbmi : 0;

-  const MB_MODE_INFO *const left_mbmi = left_mi ? &left_mi->mbmi : 0;

-  const int left_in_image = xd->left_available && left_mi;

-  const int above_in_image = xd->up_available && above_mi;

-  const int left_intra = left_in_image ? !is_inter_block(left_mbmi) : 1;

+  const MODE_INFO *const above_mi = get_above_mi(xd);

+  const MODE_INFO *const left_mi = get_left_mi(xd);

+  const MB_MODE_INFO *const above_mbmi = get_above_mbmi(above_mi);

+  const MB_MODE_INFO *const left_mbmi = get_left_mbmi(left_mi);

+  const int above_in_image = above_mi != NULL;

+  const int left_in_image = left_mi != NULL;

   const int above_intra = above_in_image ? !is_inter_block(above_mbmi) : 1;

+  const int left_intra = left_in_image ? !is_inter_block(left_mbmi) : 1;

   // Note:

   // The mode info data structure has a one element border above and to the

@@ -361,12 +369,12 @@

 // left of the entries corresponding to real blocks.

 // The prediction flags in these dummy entries are initialized to 0.

 unsigned char vp9_get_pred_context_tx_size(const MACROBLOCKD *xd) {

-  const MODE_INFO * const above_mi = xd->mi_8x8[-xd->mode_info_stride];

-  const MODE_INFO * const left_mi = xd->mi_8x8[-1];

-  const MB_MODE_INFO *const above_mbmi = above_mi ? &above_mi->mbmi : 0;

-  const MB_MODE_INFO *const left_mbmi = left_mi ? &left_mi->mbmi : 0;

-  const int left_in_image = xd->left_available && left_mi;

-  const int above_in_image = xd->up_available && above_mi;

+  const MODE_INFO *const above_mi = get_above_mi(xd);

+  const MODE_INFO *const left_mi = get_left_mi(xd);

+  const MB_MODE_INFO *const above_mbmi = get_above_mbmi(above_mi);

+  const MB_MODE_INFO *const left_mbmi = get_left_mbmi(left_mi);

+  const int above_in_image = above_mi != NULL;

+  const int left_in_image = left_mi != NULL;

   const int max_tx_size = max_txsize_lookup[xd->mi_8x8[0]->mbmi.sb_type];

   int above_context = max_tx_size;

   int left_context = max_tx_size;

--- a/vp9/common/vp9_pred_common.h

+++ b/vp9/common/vp9_pred_common.h

@@ -14,17 +14,25 @@

 #include "vp9/common/vp9_blockd.h"

 #include "vp9/common/vp9_onyxc_int.h"

+static INLINE const MODE_INFO *get_above_mi(const MACROBLOCKD *const xd) {

+  return xd->up_available ? xd->mi_8x8[-xd->mode_info_stride] : NULL;

+}

+

+static INLINE const MODE_INFO *get_left_mi(const MACROBLOCKD *const xd) {

+  return xd->left_available ? xd->mi_8x8[-1] : NULL;

+}

+

 int vp9_get_segment_id(VP9_COMMON *cm, const uint8_t *segment_ids,

                        BLOCK_SIZE bsize, int mi_row, int mi_col);

-

 static INLINE int vp9_get_pred_context_seg_id(const MACROBLOCKD *xd) {

-  const MODE_INFO * const above_mi = xd->mi_8x8[-xd->mode_info_stride];

-  const MODE_INFO * const left_mi = xd->mi_8x8[-1];

-  const int above_sip = above_mi ? above_mi->mbmi.seg_id_predicted : 0;

-  const int left_sip = left_mi ? left_mi->mbmi.seg_id_predicted : 0;

+  const MODE_INFO *const above_mi = get_above_mi(xd);

+  const MODE_INFO *const left_mi = get_left_mi(xd);

+  const int above_sip = (above_mi != NULL) ?

+                        above_mi->mbmi.seg_id_predicted : 0;

+  const int left_sip = (left_mi != NULL) ? left_mi->mbmi.seg_id_predicted : 0;

-  return above_sip + (xd->left_available ? left_sip : 0);

+  return above_sip + left_sip;

 }

 static INLINE vp9_prob vp9_get_pred_prob_seg_id(struct segmentation *seg,

@@ -35,12 +43,13 @@

 void vp9_set_pred_flag_seg_id(MACROBLOCKD *xd, uint8_t pred_flag);

 static INLINE int vp9_get_pred_context_mbskip(const MACROBLOCKD *xd) {

-  const MODE_INFO * const above_mi = xd->mi_8x8[-xd->mode_info_stride];

-  const MODE_INFO * const left_mi = xd->mi_8x8[-1];

-  const int above_skip_coeff = above_mi ? above_mi->mbmi.skip_coeff : 0;

-  const int left_skip_coeff = left_mi ? left_mi->mbmi.skip_coeff : 0;

+  const MODE_INFO *const above_mi = get_above_mi(xd);

+  const MODE_INFO *const left_mi = get_left_mi(xd);

+  const int above_skip_coeff = (above_mi != NULL) ?

+                               above_mi->mbmi.skip_coeff : 0;

+  const int left_skip_coeff = (left_mi != NULL) ? left_mi->mbmi.skip_coeff : 0;

-  return above_skip_coeff + (xd->left_available ? left_skip_coeff : 0);

+  return above_skip_coeff + left_skip_coeff;

 }

 static INLINE vp9_prob vp9_get_pred_prob_mbskip(const VP9_COMMON *cm,

--- a/vp9/decoder/vp9_decodemv.c

+++ b/vp9/decoder/vp9_decodemv.c

@@ -173,7 +173,6 @@

   MB_MODE_INFO *const mbmi = &m->mbmi;

   const BLOCK_SIZE bsize = mbmi->sb_type;

   const MODE_INFO *above_mi = xd->mi_8x8[-cm->mode_info_stride];

-  const MODE_INFO *left_mi = xd->mi_8x8[-1];

   mbmi->segment_id = read_intra_segment_id(pbi, mi_row, mi_col, r);

   mbmi->skip_coeff = read_skip_coeff(pbi, mbmi->segment_id, r);

@@ -183,8 +182,9 @@

   if (bsize >= BLOCK_8X8) {

     const MB_PREDICTION_MODE A = above_block_mode(m, above_mi, 0);

-    const MB_PREDICTION_MODE L = xd->left_available ?

-                                  left_block_mode(m, left_mi, 0) : DC_PRED;

+    const MB_PREDICTION_MODE L = xd->left_available

+                               ? left_block_mode(m, xd->mi_8x8[-1], 0)

+                               : DC_PRED;

     mbmi->mode = read_intra_mode(r, vp9_kf_y_mode_prob[A][L]);

   } else {

     // Only 4x4, 4x8, 8x4 blocks

@@ -196,8 +196,9 @@

       for (idx = 0; idx < 2; idx += num_4x4_w) {

         const int ib = idy * 2 + idx;

         const MB_PREDICTION_MODE A = above_block_mode(m, above_mi, ib);

-        const MB_PREDICTION_MODE L = (xd->left_available || idx) ?

-                                     left_block_mode(m, left_mi, ib) : DC_PRED;

+        const MB_PREDICTION_MODE L = (xd->left_available || idx)

+                                   ? left_block_mode(m, xd->mi_8x8[-1], ib)

+                                   : DC_PRED;

         const MB_PREDICTION_MODE b_mode = read_intra_mode(r,

                                               vp9_kf_y_mode_prob[A][L]);

         m->bmi[ib].as_mode = b_mode;