Clean up 4x4 coefficient decoding code.

Don't use vp9_decode_coefs_4x4() for 2nd order DC or luma blocks. The
code introduces some overhead which is unnecessary for these cases.
Also, remove variable declarations that are only used once, remove
magic offsets into the coefficient buffer (use xd->block[i].qcoeff
instead of xd->qcoeff + magic_offset), and fix a few Google Style
Guide violations.

Change-Id: I0ae653fd80ca7f1e4bccd87ecef95ddfff8f28b4

1 files changed, 63 insertions, 29 deletions

diff --git a/vp9/decoder/vp9_detokenize.c b/vp9/decoder/vp9_detokenize.c
index 46ccf627f..7434bd5f9 100644
--- a/vp9/decoder/vp9_detokenize.c
+++ b/vp9/decoder/vp9_detokenize.c
@@ -429,62 +429,92 @@ static int vp9_decode_mb_tokens_8x8(VP9D_COMP* const pbi,
   return eobtotal;
 }
 
-int vp9_decode_coefs_4x4(VP9D_COMP *dx, MACROBLOCKD *xd,
-                         BOOL_DECODER* const bc,
-                         PLANE_TYPE type, int i) {
+static int decode_coefs_4x4(VP9D_COMP *dx, MACROBLOCKD *xd,
+                            BOOL_DECODER* const bc,
+                            PLANE_TYPE type, int i, int seg_eob,
+                            TX_TYPE tx_type, const int *scan) {
   ENTROPY_CONTEXT *const A = (ENTROPY_CONTEXT *)xd->above_context;
   ENTROPY_CONTEXT *const L = (ENTROPY_CONTEXT *)xd->left_context;
   ENTROPY_CONTEXT *const a = A + vp9_block2above[i];
   ENTROPY_CONTEXT *const l = L + vp9_block2left[i];
-  INT16 *qcoeff_ptr = &xd->qcoeff[0];
-  const int *scan = vp9_default_zig_zag1d;
   unsigned short *const eobs = xd->eobs;
-  int segment_id = xd->mode_info_context->mbmi.segment_id;
-  int c, seg_eob = get_eob(xd, segment_id, 16);
-  TX_TYPE tx_type = DCT_DCT;
+  int c;
+
+  c = decode_coefs(dx, xd, bc, a, l, type, tx_type, seg_eob,
+                   xd->block[i].qcoeff, scan, TX_4X4, vp9_coef_bands);
+  eobs[i] = c;
+
+  return c;
+}
+
+static int decode_coefs_4x4_y(VP9D_COMP *dx, MACROBLOCKD *xd,
+                              BOOL_DECODER* const bc,
+                              PLANE_TYPE type, int i, int seg_eob) {
+  const TX_TYPE tx_type = (type == PLANE_TYPE_Y_WITH_DC) ?
+                          get_tx_type(xd, &xd->block[i]) : DCT_DCT;
+  const int *scan;
 
-  if (type == PLANE_TYPE_Y_WITH_DC)
-    tx_type = get_tx_type_4x4(xd, &xd->block[i]);
   switch (tx_type) {
-    case ADST_DCT :
+    case ADST_DCT:
       scan = vp9_row_scan;
       break;
-
-    case DCT_ADST :
+    case DCT_ADST:
       scan = vp9_col_scan;
       break;
-
-    default :
+    default:
       scan = vp9_default_zig_zag1d;
       break;
   }
-  eobs[i] = c = decode_coefs(dx, xd, bc, a, l, type,
-                             tx_type, seg_eob, qcoeff_ptr + i * 16,
-                             scan, TX_4X4, vp9_coef_bands);
-  return c;
+
+  return decode_coefs_4x4(dx, xd, bc, type, i, seg_eob, tx_type, scan);
 }
 
-int vp9_decode_mb_tokens_4x4_uv(VP9D_COMP* const dx,
-                                MACROBLOCKD* const xd,
-                                BOOL_DECODER* const bc) {
+int vp9_decode_coefs_4x4(VP9D_COMP *dx, MACROBLOCKD *xd,
+                         BOOL_DECODER* const bc,
+                         PLANE_TYPE type, int i) {
+  const int segment_id = xd->mode_info_context->mbmi.segment_id;
+  const int seg_eob = get_eob(xd, segment_id, 16);
+
+  return decode_coefs_4x4_y(dx, xd, bc, type, i, seg_eob);
+}
+
+static int decode_mb_tokens_4x4_uv(VP9D_COMP* const dx,
+                                   MACROBLOCKD* const xd,
+                                   BOOL_DECODER* const bc,
+                                   int seg_eob) {
   int eobtotal = 0, i;
 
-  for (i = 16; i < 24; i++)
-    eobtotal += vp9_decode_coefs_4x4(dx, xd, bc, PLANE_TYPE_UV, i);
+  // chroma blocks
+  for (i = 16; i < 24; i++) {
+    eobtotal += decode_coefs_4x4(dx, xd, bc, PLANE_TYPE_UV, i, seg_eob,
+                                 DCT_DCT, vp9_default_zig_zag1d);
+  }
 
   return eobtotal;
 }
 
+int vp9_decode_mb_tokens_4x4_uv(VP9D_COMP* const dx,
+                                MACROBLOCKD* const xd,
+                                BOOL_DECODER* const bc) {
+  const int segment_id = xd->mode_info_context->mbmi.segment_id;
+  const int seg_eob = get_eob(xd, segment_id, 16);
+
+  return decode_mb_tokens_4x4_uv(dx, xd, bc, seg_eob);
+}
+
 static int vp9_decode_mb_tokens_4x4(VP9D_COMP* const dx,
                                     MACROBLOCKD* const xd,
                                     BOOL_DECODER* const bc) {
   int i, eobtotal = 0;
   PLANE_TYPE type;
+  const int segment_id = xd->mode_info_context->mbmi.segment_id;
+  const int seg_eob = get_eob(xd, segment_id, 16);
+  const int has_2nd_order = get_2nd_order_usage(xd);
 
-  int has_2nd_order = get_2nd_order_usage(xd);
-
+  // 2nd order DC block
   if (has_2nd_order) {
-    eobtotal += vp9_decode_coefs_4x4(dx, xd, bc, PLANE_TYPE_Y2, 24) - 16;
+    eobtotal += decode_coefs_4x4(dx, xd, bc, PLANE_TYPE_Y2, 24, seg_eob,
+                                 DCT_DCT, vp9_default_zig_zag1d) - 16;
     type = PLANE_TYPE_Y_NO_DC;
   } else {
     xd->above_context->y2 = 1;
@@ -493,11 +523,15 @@ static int vp9_decode_mb_tokens_4x4(VP9D_COMP* const dx,
     type = PLANE_TYPE_Y_WITH_DC;
   }
 
+  // luma blocks
   for (i = 0; i < 16; ++i) {
-    eobtotal += vp9_decode_coefs_4x4(dx, xd, bc, type, i);
+    eobtotal += decode_coefs_4x4_y(dx, xd, bc, type, i, seg_eob);
   }
 
-  return eobtotal + vp9_decode_mb_tokens_4x4_uv(dx, xd, bc);
+  // chroma blocks
+  eobtotal += decode_mb_tokens_4x4_uv(dx, xd, bc, seg_eob);
+
+  return eobtotal;
 }
 
 int vp9_decode_mb_tokens(VP9D_COMP* const dx,