Function clinger_fast_path_impl

app/src/ThirdParty/fast_float.h:4676–4730

template <typename T>
fastfloat_really_inline FASTFLOAT_CONSTEXPR20 bool
clinger_fast_path_impl(uint64_t mantissa, int64_t exponent, bool is_negative,
                       T &value) noexcept {
  // The implementation of the Clinger's fast path is convoluted because
  // we want round-to-nearest in all cases, irrespective of the rounding mode
  // selected on the thread.
  // We proceed optimistically, assuming that detail::rounds_to_nearest()
  // returns true.
  if (binary_format<T>::min_exponent_fast_path() <= exponent &&
      exponent <= binary_format<T>::max_exponent_fast_path()) {
    // Unfortunately, the conventional Clinger's fast path is only possible
    // when the system rounds to the nearest float.
    //
    // We expect the next branch to almost always be selected.
    // We could check it first (before the previous branch), but
    // there might be performance advantages at having the check
    // be last.
    if (!cpp20_and_in_constexpr() && detail::rounds_to_nearest()) {
      // We have that fegetround() == FE_TONEAREST.
      // Next is Clinger's fast path.
      if (mantissa <= binary_format<T>::max_mantissa_fast_path()) {
        value = T(mantissa);
        if (exponent < 0) {
          value = value / binary_format<T>::exact_power_of_ten(-exponent);
        } else {
          value = value * binary_format<T>::exact_power_of_ten(exponent);
        }
        if (is_negative) {
          value = -value;
        }
        return true;
      }
    } else {
      // We do not have that fegetround() == FE_TONEAREST.
      // Next is a modified Clinger's fast path, inspired by Jakub Jelínek's
      // proposal
      if (exponent >= 0 &&
          mantissa <= binary_format<T>::max_mantissa_fast_path(exponent)) {
#if defined(__clang__) || defined(FASTFLOAT_32BIT)
        // Clang may map 0 to -0.0 when fegetround() == FE_DOWNWARD
        if (mantissa == 0) {
          value = is_negative ? T(-0.) : T(0.);
          return true;
        }
#endif
        value = T(mantissa) * binary_format<T>::exact_power_of_ten(exponent);
        if (is_negative) {
          value = -value;
        }
        return true;
      }
    }
  }
  return false;
}

/**
 * This function overload takes parsed_number_string_t structure that is created