message: Optimize normL2Sqr_ with AVX2
diff: @@ -4422,7 +4422,22 @@ int normHamming(const uchar* a, const uchar* b, int n, int cellSize)
  float normL2Sqr_(const float* a, const float* b, int n)
  {
  int j = 0; float d = 0.f;
  -#if CV_SSE
  +#if CV_AVX2
  + float CV_DECL_ALIGNED(32) buf[8];
  + __m256 d0 = _mm256_setzero_ps();
  +
  + for( ; j <= n - 8; j += 8 )
  + {
  + __m256 t0 = _mm256_sub_ps(_mm256_loadu_ps(a + j), _mm256_loadu_ps(b + j));
  +#ifdef CV_FMA3
  + d0 = _mm256_fmadd_ps(t0, t0, d0);
  +#else
  + d0 = _mm256_add_ps(d0, _mm256_mul_ps(t0, t0));
  +#endif
  + }
  + _mm256_store_ps(buf, d0);
  + d = buf[0] + buf[1] + buf[2] + buf[3] + buf[4] + buf[5] + buf[6] + buf[7];
  +#elif CV_SSE
  float CV_DECL_ALIGNED(16) buf[4];
  __m128 d0 = _mm_setzero_ps(), d1 = _mm_setzero_ps();
  