Clean up ext_interp

1) Simplify macro branch
2) Improve the naming of interp_filter read/write functions

Change-Id: I0ae290b08a8b058359874d91da468062706ab2d5
diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index 91c2b3a..9de00fc 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -2643,7 +2643,7 @@
   }
 }
 
-static InterpFilter read_interp_filter(struct aom_read_bit_buffer *rb) {
+static InterpFilter read_frame_interp_filter(struct aom_read_bit_buffer *rb) {
   return aom_rb_read_bit(rb) ? SWITCHABLE
                              : aom_rb_read_literal(rb, LOG_SWITCHABLE_FILTERS);
 }
@@ -3938,7 +3938,7 @@
 #endif
 
       cm->allow_high_precision_mv = aom_rb_read_bit(rb);
-      cm->interp_filter = read_interp_filter(rb);
+      cm->interp_filter = read_frame_interp_filter(rb);
 
       for (i = 0; i < INTER_REFS_PER_FRAME; ++i) {
         RefBuffer *const ref_buf = &cm->frame_refs[i];
diff --git a/av1/decoder/decodemv.c b/av1/decoder/decodemv.c
index 2c2d98a..fc1c8e9 100644
--- a/av1/decoder/decodemv.c
+++ b/av1/decoder/decodemv.c
@@ -1034,12 +1034,12 @@
   }
 }
 
-static INLINE InterpFilter read_interp_filter(AV1_COMMON *const cm,
-                                              MACROBLOCKD *const xd,
+static INLINE InterpFilter read_mb_interp_filter(AV1_COMMON *const cm,
+                                                 MACROBLOCKD *const xd,
 #if CONFIG_DUAL_FILTER
-                                              int dir,
+                                                 int dir,
 #endif
-                                              aom_reader *r) {
+                                                 aom_reader *r) {
 #if CONFIG_EXT_INTERP
   if (!av1_is_interp_needed(xd)) return EIGHTTAP_REGULAR;
 #endif
@@ -1563,7 +1563,7 @@
 #endif
 
 #if !CONFIG_EXT_INTERP && !CONFIG_DUAL_FILTER
-  mbmi->interp_filter = read_interp_filter(cm, xd, r);
+  mbmi->interp_filter = read_mb_interp_filter(cm, xd, r);
 #endif  // !CONFIG_EXT_INTERP && !CONFIG_DUAL_FILTER
 
   if (bsize < BLOCK_8X8) {
@@ -1787,7 +1787,7 @@
     if (has_subpel_mv_component(xd->mi[0], xd, ref) ||
         (mbmi->ref_frame[1] > INTRA_FRAME &&
          has_subpel_mv_component(xd->mi[0], xd, ref + 2)))
-      mbmi->interp_filter[ref] = read_interp_filter(cm, xd, ref, r);
+      mbmi->interp_filter[ref] = read_mb_interp_filter(cm, xd, ref, r);
   }
   // The index system worsk as:
   // (0, 1) -> (vertical, horizontal) filter types for the first ref frame.
@@ -1796,7 +1796,7 @@
   mbmi->interp_filter[3] = mbmi->interp_filter[1];
 #else
 #if CONFIG_EXT_INTERP
-  mbmi->interp_filter = read_interp_filter(cm, xd, r);
+  mbmi->interp_filter = read_mb_interp_filter(cm, xd, r);
 #endif  // CONFIG_EXT_INTERP
 #endif  // CONFIG_DUAL_FILTER
 }
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index c7ee55f..8b9d17d 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -1030,8 +1030,8 @@
 }
 #endif  // CONFIG_EXT_INTRA
 
-static void write_switchable_interp_filter(AV1_COMP *cpi, const MACROBLOCKD *xd,
-                                           aom_writer *w) {
+static void write_mb_interp_filter(AV1_COMP *cpi, const MACROBLOCKD *xd,
+                                   aom_writer *w) {
   AV1_COMMON *const cm = &cpi->common;
   const MB_MODE_INFO *const mbmi = &xd->mi[0]->mbmi;
 #if CONFIG_DUAL_FILTER
@@ -1395,7 +1395,7 @@
     }
 
 #if !CONFIG_EXT_INTERP && !CONFIG_DUAL_FILTER
-    write_switchable_interp_filter(cpi, xd, w);
+    write_mb_interp_filter(cpi, xd, w);
 #endif  // !CONFIG_EXT_INTERP
 
     if (bsize < BLOCK_8X8) {
@@ -1615,7 +1615,7 @@
 #endif  // CONFIG_EXT_INTER
 
 #if CONFIG_EXT_INTERP || CONFIG_DUAL_FILTER
-    write_switchable_interp_filter(cpi, xd, w);
+    write_mb_interp_filter(cpi, xd, w);
 #endif  // CONFIG_EXT_INTERP
   }
 
@@ -3280,8 +3280,8 @@
   }
 }
 
-static void write_interp_filter(InterpFilter filter,
-                                struct aom_write_bit_buffer *wb) {
+static void write_frame_interp_filter(InterpFilter filter,
+                                      struct aom_write_bit_buffer *wb) {
   aom_wb_write_bit(wb, filter == SWITCHABLE);
   if (filter != SWITCHABLE)
     aom_wb_write_literal(wb, filter, LOG_SWITCHABLE_FILTERS);
@@ -3983,7 +3983,7 @@
       aom_wb_write_bit(wb, cm->allow_high_precision_mv);
 
       fix_interp_filter(cm, cpi->td.counts);
-      write_interp_filter(cm->interp_filter, wb);
+      write_frame_interp_filter(cm->interp_filter, wb);
     }
   }
 
diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 2905864..c63f87a 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -53,20 +53,21 @@
 #include "av1/encoder/pvq_encoder.h"
 #endif
 #if CONFIG_DUAL_FILTER
+#define DUAL_FILTER_SET_SIZE (SWITCHABLE_FILTERS * SWITCHABLE_FILTERS)
 #if CONFIG_EXT_INTERP
-static const int filter_sets[25][2] = {
+static const int filter_sets[DUAL_FILTER_SET_SIZE][2] = {
   { 0, 0 }, { 0, 1 }, { 0, 2 }, { 0, 3 }, { 0, 4 }, { 1, 0 }, { 1, 1 },
   { 1, 2 }, { 1, 3 }, { 1, 4 }, { 2, 0 }, { 2, 1 }, { 2, 2 }, { 2, 3 },
   { 2, 4 }, { 3, 0 }, { 3, 1 }, { 3, 2 }, { 3, 3 }, { 3, 4 }, { 4, 0 },
   { 4, 1 }, { 4, 2 }, { 4, 3 }, { 4, 4 },
 };
-#else
-static const int filter_sets[9][2] = {
+#else   // CONFIG_EXT_INTERP
+static const int filter_sets[DUAL_FILTER_SET_SIZE][2] = {
   { 0, 0 }, { 0, 1 }, { 0, 2 }, { 1, 0 }, { 1, 1 },
   { 1, 2 }, { 2, 0 }, { 2, 1 }, { 2, 2 },
 };
-#endif
-#endif
+#endif  // CONFIG_EXT_INTERP
+#endif  // CONFIG_DUAL_FILTER
 
 #if CONFIG_EXT_REFS
 
@@ -7296,6 +7297,11 @@
     if (assign_filter == SWITCHABLE) {
       // do interp_filter search
       if (av1_is_interp_needed(xd)) {
+#if CONFIG_DUAL_FILTER
+        const int filter_set_size = DUAL_FILTER_SET_SIZE;
+#else
+        const int filter_set_size = SWITCHABLE_FILTERS;
+#endif
         int best_in_temp = 0;
 #if CONFIG_DUAL_FILTER
         InterpFilter best_filter[4];
@@ -7304,14 +7310,8 @@
         InterpFilter best_filter = mbmi->interp_filter;
 #endif
         restore_dst_buf(xd, tmp_dst, tmp_dst_stride);
-#if CONFIG_DUAL_FILTER
         // EIGHTTAP_REGULAR mode is calculated beforehand
-        for (i = 1; i < SWITCHABLE_FILTERS * SWITCHABLE_FILTERS; ++i)
-#else
-        // EIGHTTAP_REGULAR mode is calculated beforehand
-        for (i = 1; i < SWITCHABLE_FILTERS; ++i)
-#endif
-        {
+        for (i = 1; i < filter_set_size; ++i) {
           int tmp_skip_sb = 0;
           int64_t tmp_skip_sse = INT64_MAX;
           int tmp_rs;
@@ -10485,11 +10485,7 @@
       b_mode_info tmp_best_bmodes[16];  // Should this be 4 ?
       MB_MODE_INFO tmp_best_mbmode;
 #if CONFIG_DUAL_FILTER
-#if CONFIG_EXT_INTERP
-      BEST_SEG_INFO bsi[25];
-#else
-      BEST_SEG_INFO bsi[9];
-#endif
+      BEST_SEG_INFO bsi[DUAL_FILTER_SET_SIZE];
 #else
       BEST_SEG_INFO bsi[SWITCHABLE_FILTERS];
 #endif
@@ -10559,18 +10555,13 @@
 #endif
         } else {
 #if CONFIG_DUAL_FILTER
-          for (switchable_filter_index = 0;
-#if CONFIG_EXT_INTERP
-               switchable_filter_index < 25;
+          const int filter_set_size = DUAL_FILTER_SET_SIZE;
 #else
-               switchable_filter_index < 9;
+          const int filter_set_size = SWITCHABLE_FILTERS;
 #endif
-               ++switchable_filter_index) {
-#else
           for (switchable_filter_index = 0;
-               switchable_filter_index < SWITCHABLE_FILTERS;
+               switchable_filter_index < filter_set_size;
                ++switchable_filter_index) {
-#endif
             int newbest, rs;
             int64_t rs_rd;
             MB_MODE_INFO_EXT *mbmi_ext = x->mbmi_ext;