From baff521b634ef0d8eef16a0ab8e438092537909e Mon Sep 17 00:00:00 2001
From: Alexander Alekhin <alexander.a.alekhin@gmail.com>
Date: Wed, 15 Nov 2017 18:53:32 +0000
Subject: [PATCH] imgproc(Canny): eliminate unnecessary operations

drop manual loop unrolling:
- don't block compiler optimizations
- no effect on i5
---
 modules/imgproc/src/canny.cpp | 73 +++++++++--------------------------
 1 file changed, 18 insertions(+), 55 deletions(-)

diff --git a/modules/imgproc/src/canny.cpp b/modules/imgproc/src/canny.cpp
index b475c00e3c..6558f16923 100644
--- a/modules/imgproc/src/canny.cpp
+++ b/modules/imgproc/src/canny.cpp
@@ -812,8 +812,6 @@ public:
 
     ~finalPass() {}
 
-    finalPass& operator=(const finalPass&) {return *this;}
-
     void operator()(const Range &boundaries) const
     {
         // the final pass, form the final image
@@ -821,77 +819,39 @@ public:
         {
             int j = 0;
             uchar *pdst = dst.ptr<uchar>(i);
-            uchar *pmap;
+            const uchar *pmap = map.ptr<uchar>(i + 1);
 #if CV_SIMD128
             if(haveSIMD)
-                pmap = (uchar*)map.ptr<uchar>(i + 1) + CV_MALLOC_SIMD128;
+                pmap += CV_MALLOC_SIMD128;
             else
 #endif
-                pmap = (uchar*)map.ptr<uchar>(i + 1) + 1;
+                pmap += 1;
 #if CV_SIMD128
             if(haveSIMD) {
-                const v_int8x16 v_zero = v_setzero_s8();
+                const v_uint8x16 v_zero = v_setzero_u8();
+                const v_uint8x16 v_ff = ~v_zero;
+                const v_uint8x16 v_two(2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2);
 
-                for(; j <= dst.cols - 32; j += 32) {
-                    v_uint8x16 v_pmap1 = v_load_aligned((const unsigned char*)(pmap + j));
-                    v_uint8x16 v_pmap2 = v_load_aligned((const unsigned char*)(pmap + j + 16));
-
-                    v_uint16x8 v_pmaplo1, v_pmaphi1, v_pmaplo2, v_pmaphi2;
-                    v_expand(v_pmap1, v_pmaplo1, v_pmaphi1);
-                    v_expand(v_pmap2, v_pmaplo2, v_pmaphi2);
-
-                    v_pmaplo1 = v_pmaplo1 >> 1;
-                    v_pmaphi1 = v_pmaphi1 >> 1;
-                    v_pmaplo2 = v_pmaplo2 >> 1;
-                    v_pmaphi2 = v_pmaphi2 >> 1;
-
-                    v_pmap1 = v_pack(v_pmaplo1, v_pmaphi1);
-                    v_pmap2 = v_pack(v_pmaplo2, v_pmaphi2);
-
-                    v_pmap1 = v_reinterpret_as_u8(v_zero - v_reinterpret_as_s8(v_pmap1));
-                    v_pmap2 = v_reinterpret_as_u8(v_zero - v_reinterpret_as_s8(v_pmap2));
-
-                    v_store((pdst + j), v_pmap1);
-                    v_store((pdst + j + 16), v_pmap2);
-                }
-
-                if(j <= dst.cols - 16) {
+                for (; j <= dst.cols - 16; j += 16)
+                {
                     v_uint8x16 v_pmap = v_load_aligned((const unsigned char*)(pmap + j));
-
-                    v_uint16x8 v_pmaplo;
-                    v_uint16x8 v_pmaphi;
-                    v_expand(v_pmap, v_pmaplo, v_pmaphi);
-
-                    v_pmaplo = v_pmaplo >> 1;
-                    v_pmaphi = v_pmaphi >> 1;
-
-                    v_pmap = v_pack(v_pmaplo, v_pmaphi);
-                    v_pmap = v_reinterpret_as_u8(v_zero - v_reinterpret_as_s8(v_pmap));
-
+                    v_pmap = v_select(v_pmap == v_two, v_ff, v_zero);
                     v_store((pdst + j), v_pmap);
-                    j += 16;
                 }
 
-                if(j <= dst.cols - 8) {
-                    v_uint8x16 v_pmap = v_load_halves((const unsigned char*)(pmap + j), (const unsigned char*)(pmap + j));
-
-                    v_uint16x8 v_pmaplo;
-                    v_uint16x8 v_pmaphi;
-                    v_expand(v_pmap, v_pmaplo, v_pmaphi);
-
-                    v_pmaplo = v_pmaplo >> 1;
-                    v_pmaphi = v_pmaphi >> 1;
-
-                    v_pmap = v_pack(v_pmaplo, v_pmaphi);
-                    v_pmap = v_reinterpret_as_u8(v_zero - v_reinterpret_as_s8(v_pmap));
-
+                if (j <= dst.cols - 8)
+                {
+                    v_uint8x16 v_pmap = v_load_low((const unsigned char*)(pmap + j));
+                    v_pmap = v_select(v_pmap == v_two, v_ff, v_zero);
                     v_store_low((pdst + j), v_pmap);
                     j += 8;
                 }
             }
 #endif
             for (; j < dst.cols; j++)
+            {
                 pdst[j] = (uchar)-(pmap[j] >> 1);
+            }
         }
     }
 
@@ -901,6 +861,9 @@ private:
 #if CV_SIMD128
     bool haveSIMD;
 #endif
+
+    finalPass(const finalPass&); // = delete
+    finalPass& operator=(const finalPass&); // = delete
 };
 
 #ifdef HAVE_OPENVX