Remove obsolete impl

Author: mborland

include/boost/decimal/detail/add_impl.hpp

@@ -254,83 +254,6 @@ constexpr auto d64_add_impl(T lhs_sig, U lhs_exp, bool lhs_sign,
     return {res_sig, new_exp, new_sign};
 }
 
-template <typename ReturnType, BOOST_DECIMAL_INTEGRAL T, BOOST_DECIMAL_INTEGRAL U>
-constexpr auto d64_add_impl(T lhs_sig, U lhs_exp, bool lhs_sign,
-                            T rhs_sig, U rhs_exp, bool rhs_sign) noexcept -> ReturnType
-{
-    const bool sign {lhs_sign};
-
-    auto delta_exp {lhs_exp > rhs_exp ? lhs_exp - rhs_exp : rhs_exp - lhs_exp};
-
-    if (delta_exp > detail::precision_v<decimal64> + 1)
-    {
-        // If the difference in exponents is more than the digits of accuracy
-        // we return the larger of the two
-        //
-        // e.g. 1e20 + 1e-20 = 1e20
-
-        return {lhs_sig, lhs_exp, lhs_sign};
-    }
-    else if (delta_exp == detail::precision_v<decimal64> + 1)
-    {
-        // Only need to see if we need to add one to the
-        // significand of the bigger value
-        //
-        // e.g. 1.234567e5 + 9.876543e-2 = 1.234568e5
-
-        if (rhs_sig >= UINT64_C(5'000'000'000'000'000))
-        {
-            ++lhs_sig;
-            return {lhs_sig, lhs_exp, lhs_sign};
-        }
-        else
-        {
-            return {lhs_sig, lhs_exp, lhs_sign};
-        }
-    }
-
-    // The two numbers can be added together without special handling
-    //
-    // If we can add to the lhs sig rather than dividing we can save some precision
-    // 64-bit sign int can have 19 digits, and our normalized significand has 16
-    if (delta_exp <= 3)
-    {
-        lhs_sig *= pow10(static_cast<T>(delta_exp));
-        lhs_exp -= delta_exp;
-        delta_exp = 0;
-    }
-    else
-    {
-        lhs_sig *= 1000;
-        delta_exp -= 3;
-        lhs_exp -= 3;
-
-        if (delta_exp > 1)
-        {
-            rhs_sig /= pow10(static_cast<T>(delta_exp - 1));
-            delta_exp = 1;
-        }
-
-        if (delta_exp == 1)
-        {
-            detail::fenv_round<decimal64>(rhs_sig, rhs_sign);
-        }
-    }
-
-    // Both of the significands are well under 64-bits, so we can fit them into int64_t without issue
-    const auto new_sig {static_cast<typename ReturnType::significand_type>(lhs_sig) +
-                        static_cast<typename ReturnType::significand_type>(rhs_sig)};
-    const auto new_exp {lhs_exp};
-
-    #ifdef BOOST_DECIMAL_DEBUG_ADD
-    std::cerr << "Res Sig: " << new_sig
-              << "\nRes Exp: " << new_exp
-              << "\nRes Neg: " << sign << std::endl;
-    #endif
-
-    return {new_sig, new_exp, sign};
-}
-
 #ifdef _MSC_VER
 #  pragma warning(push)
 #  pragma warning(disable: 4127) // If constexpr macro only works for C++17 and above