Improve readability for experiment UV_LVL

Add asserts for switch.
Add helper functions to make selection of plane functions readable.
Remove extra { such that brackets match.

Change-Id: I048f3e5e0822bf1669fdcbedb84a0255139df686
diff --git a/av1/encoder/picklpf.c b/av1/encoder/picklpf.c
index 26fd55e..da15d6a 100644
--- a/av1/encoder/picklpf.c
+++ b/av1/encoder/picklpf.c
@@ -27,6 +27,16 @@
 #include "av1/encoder/encoder.h"
 #include "av1/encoder/picklpf.h"
 
+static void yv12_copy_plane(const YV12_BUFFER_CONFIG *src_bc,
+                            YV12_BUFFER_CONFIG *dst_bc, int plane) {
+  switch (plane) {
+    case 0: aom_yv12_copy_y(src_bc, dst_bc); break;
+    case 1: aom_yv12_copy_u(src_bc, dst_bc); break;
+    case 2: aom_yv12_copy_v(src_bc, dst_bc); break;
+    default: assert(plane >= 0 && plane <= 2); break;
+  }
+}
+
 int av1_get_max_filter_level(const AV1_COMP *cpi) {
   if (cpi->oxcf.pass == 2) {
     return cpi->twopass.section_intra_rating > 8 ? MAX_LOOP_FILTER * 3 / 4
@@ -49,6 +59,7 @@
 
 #if CONFIG_VAR_TX || CONFIG_EXT_PARTITION || CONFIG_CB4X4
 #if CONFIG_UV_LVL
+  assert(plane >= 0 && plane <= 2);
   av1_loop_filter_frame(cm->frame_to_show, cm, &cpi->td.mb.e_mbd, filt_level,
                         plane, partial_frame);
 #else
@@ -65,52 +76,21 @@
                           1, partial_frame);
 #endif
 
+  int highbd = 0;
+#if CONFIG_HIGHBITDEPTH
+  highbd = cm->use_highbitdepth;
+#endif  // CONFIG_HIGHBITDEPTH
+
 #if CONFIG_UV_LVL
-#if CONFIG_HIGHBITDEPTH
-  if (cm->use_highbitdepth) {
-    if (plane == 0)
-      filt_err = aom_highbd_get_y_sse(sd, cm->frame_to_show);
-    else if (plane == 1)
-      filt_err = aom_highbd_get_u_sse(sd, cm->frame_to_show);
-    else
-      filt_err = aom_highbd_get_v_sse(sd, cm->frame_to_show);
-  } else {
-    if (plane == 0)
-      filt_err = aom_get_y_sse(sd, cm->frame_to_show);
-    else if (plane == 1)
-      filt_err = aom_get_u_sse(sd, cm->frame_to_show);
-    else
-      filt_err = aom_get_v_sse(sd, cm->frame_to_show);
-  }
-#else
-  if (plane == 0)
-    filt_err = aom_get_y_sse(sd, cm->frame_to_show);
-  else if (plane == 1)
-    filt_err = aom_get_u_sse(sd, cm->frame_to_show);
-  else
-    filt_err = aom_get_v_sse(sd, cm->frame_to_show);
-#endif  // CONFIG_HIGHBITDEPTH
+  filt_err = aom_get_sse_plane(sd, cm->frame_to_show, plane, highbd);
 
   // Re-instate the unfiltered frame
-  if (plane == 0)
-    aom_yv12_copy_y(&cpi->last_frame_uf, cm->frame_to_show);
-  else if (plane == 1)
-    aom_yv12_copy_u(&cpi->last_frame_uf, cm->frame_to_show);
-  else
-    aom_yv12_copy_v(&cpi->last_frame_uf, cm->frame_to_show);
+  yv12_copy_plane(&cpi->last_frame_uf, cm->frame_to_show, plane);
 #else
-#if CONFIG_HIGHBITDEPTH
-  if (cm->use_highbitdepth) {
-    filt_err = aom_highbd_get_y_sse(sd, cm->frame_to_show);
-  } else {
-    filt_err = aom_get_y_sse(sd, cm->frame_to_show);
-  }
-#else
-  filt_err = aom_get_y_sse(sd, cm->frame_to_show);
-#endif  // CONFIG_HIGHBITDEPTH
+  filt_err = aom_get_sse_plane(sd, cm->frame_to_show, 0, highbd);
 
   // Re-instate the unfiltered frame
-  aom_yv12_copy_y(&cpi->last_frame_uf, cm->frame_to_show);
+  yv12_copy_plane(&cpi->last_frame_uf, cm->frame_to_show, 0);
 #endif  // CONFIG_UV_LVL
 
   return filt_err;
@@ -140,7 +120,7 @@
     case 0: lvl = lf->filter_level; break;
     case 1: lvl = lf->filter_level_u; break;
     case 2: lvl = lf->filter_level_v; break;
-    default: lvl = lf->filter_level; break;
+    default: assert(plane >= 0 && plane <= 2); return 0;
   }
   int filt_mid = clamp(lvl, min_filter_level, max_filter_level);
 #else
@@ -154,12 +134,7 @@
   memset(ss_err, 0xFF, sizeof(ss_err));
 
 #if CONFIG_UV_LVL
-  if (plane == 0)
-    aom_yv12_copy_y(cm->frame_to_show, &cpi->last_frame_uf);
-  else if (plane == 1)
-    aom_yv12_copy_u(cm->frame_to_show, &cpi->last_frame_uf);
-  else if (plane == 2)
-    aom_yv12_copy_v(cm->frame_to_show, &cpi->last_frame_uf);
+  yv12_copy_plane(cm->frame_to_show, &cpi->last_frame_uf, plane);
 #else
   //  Make a copy of the unfiltered / processed recon buffer
   aom_yv12_copy_y(cm->frame_to_show, &cpi->last_frame_uf);