Add function for x86 architecture

Author: nicodr97

source/Platform/x86/AVX2.cpp

@@ -102,11 +102,19 @@ class AVX2Vector {
     return AVX2Vector(_mm256_andnot_si256(rhs.vector, vector));
   }
 
+  #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));
     return _mm_extract_epi64(sum128, 0) + _mm_extract_epi64(sum128, 1);
   }
+#else
+  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));
+    return _mm_extract_epi32(sum128, 0) + _mm_extract_epi32(sum128, 1);
+  }
+#endif
 
   inline void clear() { vector = _mm256_setzero_si256(); }
 };