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Reduce dqcoeff array size in decoder

The decoding process handles detokenization and reconstruction per
transform block sequentially. There is no need to offset the dqcoeff
buffer according to the transform block index. This allows to
reduce the memory spill and improve cache performance.

Change-Id: Ibb8bfe532a7a08fcabaf6d42cbec1e986901d32d

--- a/vp9/common/vp9_blockd.h

+++ b/vp9/common/vp9_blockd.h

@@ -188,8 +188,11 @@

 #endif

   /* dqcoeff are shared by all the planes. So planes must be decoded serially */

+#if CONFIG_VP9_ENCODER

   DECLARE_ALIGNED(16, tran_low_t, dqcoeff[64 * 64]);

-

+#else

+  DECLARE_ALIGNED(16, tran_low_t, dqcoeff[32 * 32]);

+#endif

   int lossless;

   int corrupted;

--- a/vp9/decoder/vp9_decodeframe.c

+++ b/vp9/decoder/vp9_decodeframe.c

@@ -188,7 +188,7 @@

   struct macroblockd_plane *const pd = &xd->plane[plane];

   if (eob > 0) {

     TX_TYPE tx_type = DCT_DCT;

-    tran_low_t *const dqcoeff = BLOCK_OFFSET(pd->dqcoeff, block);

+    tran_low_t *const dqcoeff = pd->dqcoeff;

 #if CONFIG_VP9_HIGHBITDEPTH

     if (xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH) {

       if (xd->lossless) {

--- a/vp9/decoder/vp9_detokenize.c

+++ b/vp9/decoder/vp9_detokenize.c

@@ -217,7 +217,7 @@

                                                pd->left_context + y);

   const scan_order *so = get_scan(xd, tx_size, pd->plane_type, block);

   const int eob = decode_coefs(xd, pd->plane_type,

-                               BLOCK_OFFSET(pd->dqcoeff, block), tx_size,

+                               pd->dqcoeff, tx_size,

                                dequant, ctx, so->scan, so->neighbors, r);

   vp9_set_contexts(xd, pd, plane_bsize, tx_size, eob > 0, x, y);

   return eob;

-- 

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