Merge "Cleaning vp9_variance.{c, h}."

2 files changed, 119 insertions, 236 deletions

diff --git a/vp9/encoder/vp9_variance.c b/vp9/encoder/vp9_variance.c
index 71867a938..a31a476f3 100644
--- a/vp9/encoder/vp9_variance.c
+++ b/vp9/encoder/vp9_variance.c
@@ -18,63 +18,34 @@
 
 #include "vp9/encoder/vp9_variance.h"
 
-void variance(const uint8_t *src_ptr,
-              int  source_stride,
-              const uint8_t *ref_ptr,
-              int  recon_stride,
-              int  w,
-              int  h,
-              unsigned int *sse,
-              int *sum) {
+void variance(const uint8_t *a, int  a_stride,
+              const uint8_t *b, int  b_stride,
+              int  w, int  h, unsigned int *sse, int *sum) {
   int i, j;
-  int diff;
 
   *sum = 0;
   *sse = 0;
 
   for (i = 0; i < h; i++) {
     for (j = 0; j < w; j++) {
-      diff = src_ptr[j] - ref_ptr[j];
+      const int diff = a[j] - b[j];
       *sum += diff;
       *sse += diff * diff;
     }
 
-    src_ptr += source_stride;
-    ref_ptr += recon_stride;
+    a += a_stride;
+    b += b_stride;
   }
 }
 
-/****************************************************************************
- *
- *  ROUTINE       : filter_block2d_bil_first_pass
- *
- *  INPUTS        : uint8_t  *src_ptr          : Pointer to source block.
- *                  uint32_t src_pixels_per_line : Stride of input block.
- *                  uint32_t pixel_step        : Offset between filter input
- *                                               samples (see notes).
- *                  uint32_t output_height     : Input block height.
- *                  uint32_t output_width      : Input block width.
- *                  int32_t  *vp9_filter       : Array of 2 bi-linear filter
- *                                               taps.
- *
- *  OUTPUTS       : int32_t *output_ptr        : Pointer to filtered block.
- *
- *  RETURNS       : void
- *
- *  FUNCTION      : Applies a 1-D 2-tap bi-linear filter to the source block in
- *                  either horizontal or vertical direction to produce the
- *                  filtered output block. Used to implement first-pass
- *                  of 2-D separable filter.
- *
- *  SPECIAL NOTES : Produces int32_t output to retain precision for next pass.
- *                  Two filter taps should sum to VP9_FILTER_WEIGHT.
- *                  pixel_step defines whether the filter is applied
- *                  horizontally (pixel_step=1) or vertically (pixel_step=
- *                  stride).
- *                  It defines the offset required to move from one input
- *                  to the next.
- *
- ****************************************************************************/
+// Applies a 1-D 2-tap bi-linear filter to the source block in either horizontal
+// or vertical direction to produce the filtered output block. Used to implement
+// first-pass of 2-D separable filter.
+//
+// Produces int32_t output to retain precision for next pass. Two filter taps
+// should sum to VP9_FILTER_WEIGHT. pixel_step defines whether the filter is
+// applied horizontally (pixel_step=1) or vertically (pixel_step=stride). It
+// defines the offset required to move from one input to the next.
 static void var_filter_block2d_bil_first_pass(const uint8_t *src_ptr,
                                               uint16_t *output_ptr,
                                               unsigned int src_pixels_per_line,
@@ -99,38 +70,14 @@ static void var_filter_block2d_bil_first_pass(const uint8_t *src_ptr,
   }
 }
 
-/****************************************************************************
- *
- *  ROUTINE       : filter_block2d_bil_second_pass
- *
- *  INPUTS        : int32_t  *src_ptr          : Pointer to source block.
- *                  uint32_t src_pixels_per_line : Stride of input block.
- *                  uint32_t pixel_step        : Offset between filter input
- *                                               samples (see notes).
- *                  uint32_t output_height     : Input block height.
- *                  uint32_t output_width      : Input block width.
- *                  int32_t  *vp9_filter       : Array of 2 bi-linear filter
- *                                               taps.
- *
- *  OUTPUTS       : uint16_t *output_ptr       : Pointer to filtered block.
- *
- *  RETURNS       : void
- *
- *  FUNCTION      : Applies a 1-D 2-tap bi-linear filter to the source block in
- *                  either horizontal or vertical direction to produce the
- *                  filtered output block. Used to implement second-pass
- *                  of 2-D separable filter.
- *
- *  SPECIAL NOTES : Requires 32-bit input as produced by
- *                  filter_block2d_bil_first_pass.
- *                  Two filter taps should sum to VP9_FILTER_WEIGHT.
- *                  pixel_step defines whether the filter is applied
- *                  horizontally (pixel_step=1) or vertically (pixel_step=
- *                  stride).
- *                  It defines the offset required to move from one input
- *                  to the next.
- *
- ****************************************************************************/
+// Applies a 1-D 2-tap bi-linear filter to the source block in either horizontal
+// or vertical direction to produce the filtered output block. Used to implement
+// second-pass of 2-D separable filter.
+//
+// Requires 32-bit input as produced by filter_block2d_bil_first_pass. Two
+// filter taps should sum to VP9_FILTER_WEIGHT. pixel_step defines whether the
+// filter is applied horizontally (pixel_step=1) or vertically (pixel_step=
+// stride). It defines the offset required to move from one input to the next.
 static void var_filter_block2d_bil_second_pass(const uint16_t *src_ptr,
                                                uint8_t *output_ptr,
                                                unsigned int src_pixels_per_line,
@@ -156,9 +103,8 @@ static void var_filter_block2d_bil_second_pass(const uint16_t *src_ptr,
 unsigned int vp9_get_mb_ss_c(const int16_t *src_ptr) {
   unsigned int i, sum = 0;
 
-  for (i = 0; i < 256; i++) {
-    sum += (src_ptr[i] * src_ptr[i]);
-  }
+  for (i = 0; i < 256; i++)
+    sum += src_ptr[i] * src_ptr[i];
 
   return sum;
 }
@@ -183,12 +129,10 @@ unsigned int vp9_sub_pixel_variance64x32_c(const uint8_t *src_ptr,
                                            const uint8_t *dst_ptr,
                                            int dst_pixels_per_line,
                                            unsigned int *sse) {
-  uint16_t fdata3[65 * 64];  // Temp data buffer used in filtering
+  uint16_t fdata3[65 * 64];
   uint8_t temp2[68 * 64];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 33, 64, hfilter);
@@ -205,13 +149,11 @@ unsigned int vp9_sub_pixel_avg_variance64x32_c(const uint8_t *src_ptr,
                                                int dst_pixels_per_line,
                                                unsigned int *sse,
                                                const uint8_t *second_pred) {
-  uint16_t fdata3[65 * 64];  // Temp data buffer used in filtering
+  uint16_t fdata3[65 * 64];
   uint8_t temp2[68 * 64];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 64 * 64);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 64 * 64);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 33, 64, hfilter);
@@ -240,12 +182,10 @@ unsigned int vp9_sub_pixel_variance32x64_c(const uint8_t *src_ptr,
                                            const uint8_t *dst_ptr,
                                            int dst_pixels_per_line,
                                            unsigned int *sse) {
-  uint16_t fdata3[65 * 64];  // Temp data buffer used in filtering
+  uint16_t fdata3[65 * 64];
   uint8_t temp2[68 * 64];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 65, 32, hfilter);
@@ -262,13 +202,11 @@ unsigned int vp9_sub_pixel_avg_variance32x64_c(const uint8_t *src_ptr,
                                                int dst_pixels_per_line,
                                                unsigned int *sse,
                                                const uint8_t *second_pred) {
-  uint16_t fdata3[65 * 64];  // Temp data buffer used in filtering
+  uint16_t fdata3[65 * 64];
   uint8_t temp2[68 * 64];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 32 * 64);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 32 * 64);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 65, 32, hfilter);
@@ -297,12 +235,10 @@ unsigned int vp9_sub_pixel_variance32x16_c(const uint8_t *src_ptr,
                                            const uint8_t *dst_ptr,
                                            int dst_pixels_per_line,
                                            unsigned int *sse) {
-  uint16_t fdata3[33 * 32];  // Temp data buffer used in filtering
+  uint16_t fdata3[33 * 32];
   uint8_t temp2[36 * 32];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 17, 32, hfilter);
@@ -319,13 +255,11 @@ unsigned int vp9_sub_pixel_avg_variance32x16_c(const uint8_t *src_ptr,
                                                int dst_pixels_per_line,
                                                unsigned int *sse,
                                                const uint8_t *second_pred) {
-  uint16_t fdata3[33 * 32];  // Temp data buffer used in filtering
+  uint16_t fdata3[33 * 32];
   uint8_t temp2[36 * 32];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 32 * 16);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 32 * 16);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 17, 32, hfilter);
@@ -354,12 +288,10 @@ unsigned int vp9_sub_pixel_variance16x32_c(const uint8_t *src_ptr,
                                            const uint8_t *dst_ptr,
                                            int dst_pixels_per_line,
                                            unsigned int *sse) {
-  uint16_t fdata3[33 * 32];  // Temp data buffer used in filtering
+  uint16_t fdata3[33 * 32];
   uint8_t temp2[36 * 32];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 33, 16, hfilter);
@@ -376,13 +308,11 @@ unsigned int vp9_sub_pixel_avg_variance16x32_c(const uint8_t *src_ptr,
                                                int dst_pixels_per_line,
                                                unsigned int *sse,
                                                const uint8_t *second_pred) {
-  uint16_t fdata3[33 * 32];  // Temp data buffer used in filtering
+  uint16_t fdata3[33 * 32];
   uint8_t temp2[36 * 32];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 16 * 32);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 16 * 32);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 33, 16, hfilter);
@@ -582,17 +512,12 @@ unsigned int vp9_sub_pixel_variance4x4_c(const uint8_t *src_ptr,
                                          int dst_pixels_per_line,
                                          unsigned int *sse) {
   uint8_t temp2[20 * 16];
-  const int16_t *hfilter, *vfilter;
-  uint16_t fdata3[5 * 4];  // Temp data buffer used in filtering
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  uint16_t fdata3[5 * 4];
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
-  // First filter 1d Horizontal
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 5, 4, hfilter);
-
-  // Now filter Verticaly
   var_filter_block2d_bil_second_pass(fdata3, temp2, 4,  4,  4,  4, vfilter);
 
   return vp9_variance4x4(temp2, 4, dst_ptr, dst_pixels_per_line, sse);
@@ -607,18 +532,13 @@ unsigned int vp9_sub_pixel_avg_variance4x4_c(const uint8_t *src_ptr,
                                              unsigned int *sse,
                                              const uint8_t *second_pred) {
   uint8_t temp2[20 * 16];
-  const int16_t *hfilter, *vfilter;
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 4 * 4);  // compound pred buffer
-  uint16_t fdata3[5 * 4];  // Temp data buffer used in filtering
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 4 * 4);
+  uint16_t fdata3[5 * 4];
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
-  // First filter 1d Horizontal
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 5, 4, hfilter);
-
-  // Now filter Verticaly
   var_filter_block2d_bil_second_pass(fdata3, temp2, 4,  4,  4,  4, vfilter);
   vp9_comp_avg_pred(temp3, second_pred, 4, 4, temp2, 4);
   return vp9_variance4x4(temp3, 4, dst_ptr, dst_pixels_per_line, sse);
@@ -631,17 +551,14 @@ unsigned int vp9_sub_pixel_variance8x8_c(const uint8_t *src_ptr,
                                          const uint8_t *dst_ptr,
                                          int dst_pixels_per_line,
                                          unsigned int *sse) {
-  uint16_t fdata3[9 * 8];  // Temp data buffer used in filtering
+  uint16_t fdata3[9 * 8];
   uint8_t temp2[20 * 16];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 9, 8, hfilter);
   var_filter_block2d_bil_second_pass(fdata3, temp2, 8, 8, 8, 8, vfilter);
-
   return vp9_variance8x8(temp2, 8, dst_ptr, dst_pixels_per_line, sse);
 }
 
@@ -653,18 +570,17 @@ unsigned int vp9_sub_pixel_avg_variance8x8_c(const uint8_t *src_ptr,
                                              int dst_pixels_per_line,
                                              unsigned int *sse,
                                              const uint8_t *second_pred) {
-  uint16_t fdata3[9 * 8];  // Temp data buffer used in filtering
+  uint16_t fdata3[9 * 8];
   uint8_t temp2[20 * 16];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 8 * 8);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 8 * 8);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 9, 8, hfilter);
   var_filter_block2d_bil_second_pass(fdata3, temp2, 8, 8, 8, 8, vfilter);
   vp9_comp_avg_pred(temp3, second_pred, 8, 8, temp2, 8);
+
   return vp9_variance8x8(temp3, 8, dst_ptr, dst_pixels_per_line, sse);
 }
 
@@ -675,12 +591,10 @@ unsigned int vp9_sub_pixel_variance16x16_c(const uint8_t *src_ptr,
                                            const uint8_t *dst_ptr,
                                            int dst_pixels_per_line,
                                            unsigned int *sse) {
-  uint16_t fdata3[17 * 16];  // Temp data buffer used in filtering
+  uint16_t fdata3[17 * 16];
   uint8_t temp2[20 * 16];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 17, 16, hfilter);
@@ -699,11 +613,9 @@ unsigned int vp9_sub_pixel_avg_variance16x16_c(const uint8_t *src_ptr,
                                                const uint8_t *second_pred) {
   uint16_t fdata3[17 * 16];
   uint8_t temp2[20 * 16];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 16 * 16);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 16 * 16);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 17, 16, hfilter);
@@ -722,10 +634,8 @@ unsigned int vp9_sub_pixel_variance64x64_c(const uint8_t *src_ptr,
                                            unsigned int *sse) {
   uint16_t fdata3[65 * 64];  // Temp data buffer used in filtering
   uint8_t temp2[68 * 64];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 65, 64, hfilter);
@@ -742,13 +652,11 @@ unsigned int vp9_sub_pixel_avg_variance64x64_c(const uint8_t *src_ptr,
                                                int dst_pixels_per_line,
                                                unsigned int *sse,
                                                const uint8_t *second_pred) {
-  uint16_t fdata3[65 * 64];  // Temp data buffer used in filtering
+  uint16_t fdata3[65 * 64];
   uint8_t temp2[68 * 64];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 64 * 64);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 64 * 64);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 65, 64, hfilter);
@@ -764,12 +672,10 @@ unsigned int vp9_sub_pixel_variance32x32_c(const uint8_t *src_ptr,
                                            const uint8_t *dst_ptr,
                                            int dst_pixels_per_line,
                                            unsigned int *sse) {
-  uint16_t fdata3[33 * 32];  // Temp data buffer used in filtering
+  uint16_t fdata3[33 * 32];
   uint8_t temp2[36 * 32];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 33, 32, hfilter);
@@ -786,13 +692,11 @@ unsigned int vp9_sub_pixel_avg_variance32x32_c(const uint8_t *src_ptr,
                                                int dst_pixels_per_line,
                                                unsigned int *sse,
                                                const uint8_t *second_pred) {
-  uint16_t fdata3[33 * 32];  // Temp data buffer used in filtering
+  uint16_t fdata3[33 * 32];
   uint8_t temp2[36 * 32];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 32 * 32);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 32 * 32);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 33, 32, hfilter);
@@ -928,12 +832,10 @@ unsigned int vp9_sub_pixel_variance16x8_c(const uint8_t *src_ptr,
                                           const uint8_t *dst_ptr,
                                           int dst_pixels_per_line,
                                           unsigned int *sse) {
-  uint16_t fdata3[16 * 9];  // Temp data buffer used in filtering
+  uint16_t fdata3[16 * 9];
   uint8_t temp2[20 * 16];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 9, 16, hfilter);
@@ -950,13 +852,11 @@ unsigned int vp9_sub_pixel_avg_variance16x8_c(const uint8_t *src_ptr,
                                               int dst_pixels_per_line,
                                               unsigned int *sse,
                                               const uint8_t *second_pred) {
-  uint16_t fdata3[16 * 9];  // Temp data buffer used in filtering
+  uint16_t fdata3[16 * 9];
   uint8_t temp2[20 * 16];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 16 * 8);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 16 * 8);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 9, 16, hfilter);
@@ -974,10 +874,8 @@ unsigned int vp9_sub_pixel_variance8x16_c(const uint8_t *src_ptr,
                                           unsigned int *sse) {
   uint16_t fdata3[9 * 16];  // Temp data buffer used in filtering
   uint8_t temp2[20 * 16];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 17, 8, hfilter);
@@ -994,13 +892,11 @@ unsigned int vp9_sub_pixel_avg_variance8x16_c(const uint8_t *src_ptr,
                                               int dst_pixels_per_line,
                                               unsigned int *sse,
                                               const uint8_t *second_pred) {
-  uint16_t fdata3[9 * 16];  // Temp data buffer used in filtering
+  uint16_t fdata3[9 * 16];
   uint8_t temp2[20 * 16];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 8 * 16);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 8 * 16);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 17, 8, hfilter);
@@ -1016,12 +912,10 @@ unsigned int vp9_sub_pixel_variance8x4_c(const uint8_t *src_ptr,
                                          const uint8_t *dst_ptr,
                                          int dst_pixels_per_line,
                                          unsigned int *sse) {
-  uint16_t fdata3[8 * 5];  // Temp data buffer used in filtering
+  uint16_t fdata3[8 * 5];
   uint8_t temp2[20 * 16];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 5, 8, hfilter);
@@ -1038,13 +932,11 @@ unsigned int vp9_sub_pixel_avg_variance8x4_c(const uint8_t *src_ptr,
                                              int dst_pixels_per_line,
                                              unsigned int *sse,
                                              const uint8_t *second_pred) {
-  uint16_t fdata3[8 * 5];  // Temp data buffer used in filtering
+  uint16_t fdata3[8 * 5];
   uint8_t temp2[20 * 16];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 8 * 4);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 8 * 4);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 5, 8, hfilter);
@@ -1060,14 +952,12 @@ unsigned int vp9_sub_pixel_variance4x8_c(const uint8_t *src_ptr,
                                          const uint8_t *dst_ptr,
                                          int dst_pixels_per_line,
                                          unsigned int *sse) {
-  uint16_t fdata3[5 * 8];  // Temp data buffer used in filtering
+  uint16_t fdata3[5 * 8];
   // FIXME(jingning,rbultje): this temp2 buffer probably doesn't need to be
   // of this big? same issue appears in all other block size settings.
   uint8_t temp2[20 * 16];
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 9, 4, hfilter);
@@ -1084,13 +974,11 @@ unsigned int vp9_sub_pixel_avg_variance4x8_c(const uint8_t *src_ptr,
                                              int dst_pixels_per_line,
                                              unsigned int *sse,
                                              const uint8_t *second_pred) {
-  uint16_t fdata3[5 * 8];  // Temp data buffer used in filtering
+  uint16_t fdata3[5 * 8];
   uint8_t temp2[20 * 16];
-  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 4 * 8);  // compound pred buffer
-  const int16_t *hfilter, *vfilter;
-
-  hfilter = BILINEAR_FILTERS_2TAP(xoffset);
-  vfilter = BILINEAR_FILTERS_2TAP(yoffset);
+  DECLARE_ALIGNED_ARRAY(16, uint8_t, temp3, 4 * 8);
+  const int16_t *const hfilter = BILINEAR_FILTERS_2TAP(xoffset);
+  const int16_t *const vfilter = BILINEAR_FILTERS_2TAP(yoffset);
 
   var_filter_block2d_bil_first_pass(src_ptr, fdata3, src_pixels_per_line,
                                     1, 9, 4, hfilter);
@@ -1106,9 +994,8 @@ void vp9_comp_avg_pred(uint8_t *comp_pred, const uint8_t *pred, int width,
 
   for (i = 0; i < height; i++) {
     for (j = 0; j < width; j++) {
-      int tmp;
-      tmp = pred[j] + ref[j];
-      comp_pred[j] = (tmp + 1) >> 1;
+      const int tmp = pred[j] + ref[j];
+      comp_pred[j] = ROUND_POWER_OF_TWO(tmp, 1);
     }
     comp_pred += width;
     pred += width;
diff --git a/vp9/encoder/vp9_variance.h b/vp9/encoder/vp9_variance.h
index c9e39a1a2..4c8be71cd 100644
--- a/vp9/encoder/vp9_variance.h
+++ b/vp9/encoder/vp9_variance.h
@@ -17,14 +17,10 @@
 extern "C" {
 #endif
 
-void variance(const uint8_t *src_ptr,
-              int  source_stride,
-              const uint8_t *ref_ptr,
-              int  recon_stride,
-              int  w,
-              int  h,
-              unsigned int *sse,
-              int *sum);
+void variance(const uint8_t *a, int a_stride,
+              const uint8_t *b, int b_stride,
+              int  w, int  h,
+              unsigned int *sse, int *sum);
 
 typedef unsigned int(*vp9_sad_fn_t)(const uint8_t *src_ptr,
                                     int source_stride,