Improve od_dering_simd_sse4_1

Change-Id: I6173dfb181777343d254aef880a8c9d379206556

av1/common/od_dering_simd.h

@@ -179,18 +179,11 @@ int SIMD_FUNC(od_dir_find8)(const od_dering_in *img, int stride, int32_t *var,
   __m128i max = _mm_max_epi32(dir03, dir47);
   max = _mm_max_epi32(max, _mm_shuffle_epi32(max, _MM_SHUFFLE(1, 0, 3, 2)));
   max = _mm_max_epi32(max, _mm_shuffle_epi32(max, _MM_SHUFFLE(2, 3, 0, 1)));
-  dir03 = _mm_and_si128(_mm_cmpeq_epi32(max, dir03),
-                        _mm_setr_epi32(-1, -2, -3, -4));
-  dir47 = _mm_and_si128(_mm_cmpeq_epi32(max, dir47),
-                        _mm_setr_epi32(-5, -6, -7, -8));
-  dir03 = _mm_max_epu32(dir03, dir47);
-  dir03 = _mm_max_epu32(dir03, _mm_unpackhi_epi64(dir03, dir03));
-  dir03 =
-      _mm_max_epu32(dir03, _mm_shufflelo_epi16(dir03, _MM_SHUFFLE(1, 0, 3, 2)));
-  dir03 = _mm_xor_si128(dir03, _mm_set1_epi32(0xFFFFFFFF));
-
-  best_dir = _mm_cvtsi128_si32(dir03);
   best_cost = _mm_cvtsi128_si32(max);
+  __m128i t =
+      _mm_packs_epi32(_mm_cmpeq_epi32(max, dir03), _mm_cmpeq_epi32(max, dir47));
+  best_dir = _mm_movemask_epi8(_mm_packs_epi16(t, t));
+  best_dir = get_msb(best_dir ^ (best_dir - 1));  // Count trailing zeros
 #else
   /* Compute "mostly vertical" directions. */
   compute_directions(lines, cost + 4);