Function CTZ

Bcore/src/main/cpp/base/bit_utils.h:68–76

template<typename T>
constexpr int CTZ(T x) {
  static_assert(std::is_integral<T>::value, "T must be integral");
  // It is not unreasonable to ask for trailing zeros in a negative number. As such, do not check
  // that T is an unsigned type.
  static_assert(sizeof(T) == sizeof(uint64_t) || sizeof(T) <= sizeof(uint32_t),
                "Unsupported sizeof(T)");
  DCHECK_NE(x, static_cast<T>(0));
  return (sizeof(T) == sizeof(uint64_t)) ? __builtin_ctzll(x) : __builtin_ctz(x);
}

// Similar to CTZ except that on zero input it returns bitwidth and supports signed integers.
template<typename T>