Function hsum_float_8

ggml-quants.c:67–73

horizontally add 8 floats

#if __AVX__ || __AVX2__ || __AVX512F__
// horizontally add 8 floats
static inline float hsum_float_8(const __m256 x) {
    __m128 res = _mm256_extractf128_ps(x, 1);
    res = _mm_add_ps(res, _mm256_castps256_ps128(x));
    res = _mm_add_ps(res, _mm_movehl_ps(res, res));
    res = _mm_add_ss(res, _mm_movehdup_ps(res));
    return _mm_cvtss_f32(res);
}

// horizontally add 8 int32_t
static inline int hsum_i32_8(const __m256i a) {