check_cxx_source_runs("
      #include <immintrin.h>
      int main()
      {
        __m256 a, b;
        float vals[8] = {1, 2, 3, 4, 5, 6, 7, 8};
        const int mask = 123;
        a = _mm256_loadu_ps(vals);
        b = a;
        b = _mm256_dp_ps (a, a, 3);
        _mm256_storeu_ps(vals,b);
        return 0;
      }"
            HAVE_AVX_EXTENSIONS)

elseif(HAVE_AVX_EXTENSIONS)