Function CLZ

Bcore/src/main/cpp/base/bit_utils.h:46–57

template<typename T>
constexpr int CLZ(T x) {
  static_assert(std::is_integral<T>::value, "T must be integral");
  static_assert(std::is_unsigned<T>::value, "T must be unsigned");
  static_assert(std::numeric_limits<T>::radix == 2, "Unexpected radix!");
  static_assert(sizeof(T) == sizeof(uint64_t) || sizeof(T) <= sizeof(uint32_t),
                "Unsupported sizeof(T)");
  DCHECK_NE(x, 0u);
  constexpr bool is_64_bit = (sizeof(T) == sizeof(uint64_t));
  constexpr size_t adjustment =
      is_64_bit ? 0u : std::numeric_limits<uint32_t>::digits - std::numeric_limits<T>::digits;
  return is_64_bit ? __builtin_clzll(x) : __builtin_clz(x) - adjustment;
}

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