template <endianness big_endian>
std::pair<const char *, char16_t *>
arm_convert_latin1_to_utf16(const char *buf, size_t len,
                            char16_t *utf16_output) {
  const char *end = buf + len;

  while (end - buf >= 16) {
    uint8x16_t in8 = vld1q_u8(reinterpret_cast<const uint8_t *>(buf));
    uint16x8_t inlow = vmovl_u8(vget_low_u8(in8));
    if simdutf_constexpr (!match_system(big_endian)) {
      inlow = vreinterpretq_u16_u8(vrev16q_u8(vreinterpretq_u8_u16(inlow)));
    }
    vst1q_u16(reinterpret_cast<uint16_t *>(utf16_output), inlow);
    uint16x8_t inhigh = vmovl_u8(vget_high_u8(in8));
    if simdutf_constexpr (!match_system(big_endian)) {
      inhigh = vreinterpretq_u16_u8(vrev16q_u8(vreinterpretq_u8_u16(inhigh)));
    }
    vst1q_u16(reinterpret_cast<uint16_t *>(utf16_output + 8), inhigh);
    utf16_output += 16;
    buf += 16;
  }

  return std::make_pair(buf, utf16_output);
}