u16x16_from_u8x16() and i16x16_from_i8x16() call intrisics
_mm256_cvtepu8_epi64 and _mm256_cvtepi8_epi64. But they are not seems
doing the right data conversion from the name of the wrappers.
The correct intrinsics been called should be _mm256_cvtepu8_epi16
and _mm256_cvtepi8_epi16.