Fix AVX2 function

Author: nicodr97

source/Platform/x86/AVX2.cpp

@@ -102,7 +102,7 @@ class AVX2Vector {
     return AVX2Vector(_mm256_andnot_si256(rhs.vector, vector));
   }
 
-  #ifdef CPU_FEATURES_ARCH_X86_64
+#ifdef CPU_FEATURES_ARCH_X86_64
   inline uint16_t sum() const {
     __m256i sum256 = _mm256_sad_epu8(vector, _mm256_setzero_si256());
     __m128i sum128 = _mm_add_epi64(_mm256_extractf128_si256(sum256, 1), _mm256_castsi256_si128(sum256));
@@ -111,7 +111,7 @@ class AVX2Vector {
 #else
   inline uint16_t sum() const {
     __m256i sum256 = _mm256_sad_epu8(vector, _mm256_setzero_si256());
-    __m128i sum128 = _mm_add_epi32(_mm256_extractf128_si256(sum256, 1), _mm256_castsi256_si128(sum256));
+    __m128i sum128 = _mm_add_epi64(_mm256_extractf128_si256(sum256, 1), _mm256_castsi256_si128(sum256));
     return _mm_extract_epi32(sum128, 0) + _mm_extract_epi32(sum128, 1) + _mm_extract_epi32(sum128, 2) + _mm_extract_epi32(sum128, 3);
   }
 #endif