Enhance multiplication

Author: mborland

include/boost/decimal/decimal128.hpp

@@ -1937,21 +1937,15 @@ constexpr auto operator*(decimal128 lhs, decimal128 rhs) noexcept -> decimal128
 
     auto lhs_sig {lhs.full_significand()};
     auto lhs_exp {lhs.biased_exponent()};
-
-    while (lhs_sig % 10 == 0 && lhs_sig != 0)
-    {
-        lhs_sig /= 10;
-        ++lhs_exp;
-    }
+    const auto lhs_zeros {detail::remove_trailing_zeros(lhs_sig)};
+    lhs_sig = lhs_zeros.trimmed_number;
+    lhs_exp += static_cast<std::int32_t>(lhs_zeros.number_of_removed_zeros);
 
     auto rhs_sig {rhs.full_significand()};
     auto rhs_exp {rhs.biased_exponent()};
-
-    while (rhs_sig % 10 == 0 && rhs_sig != 0)
-    {
-        rhs_sig /= 10;
-        ++rhs_exp;
-    }
+    const auto rhs_zeros {detail::remove_trailing_zeros(rhs_sig)};
+    rhs_sig = rhs_zeros.trimmed_number;
+    rhs_exp += static_cast<std::int32_t>(rhs_zeros.number_of_removed_zeros);
 
     const auto result {d128_mul_impl(lhs_sig, lhs_exp, lhs.isneg(),
                                      rhs_sig, rhs_exp, rhs.isneg())};
@@ -1970,20 +1964,16 @@ constexpr auto operator*(decimal128 lhs, Integer rhs) noexcept
 
     auto lhs_sig {lhs.full_significand()};
     auto lhs_exp {lhs.biased_exponent()};
-    while (lhs_sig % 10 == 0 && lhs_sig != 0)
-    {
-        lhs_sig /= 10;
-        ++lhs_exp;
-    }
+    const auto lhs_zeros {detail::remove_trailing_zeros(lhs_sig)};
+    lhs_sig = lhs_zeros.trimmed_number;
+    lhs_exp += static_cast<std::int32_t>(lhs_zeros.number_of_removed_zeros);
     auto lhs_components {detail::decimal128_components{lhs_sig, lhs_exp, lhs.isneg()}};
 
     auto rhs_sig {static_cast<detail::uint128>(detail::make_positive_unsigned(rhs))};
     std::int32_t rhs_exp {0};
-    while (rhs_sig % 10 == 0 && rhs_sig != 0)
-    {
-        rhs_sig /= 10;
-        ++rhs_exp;
-    }
+    const auto rhs_zeros {detail::remove_trailing_zeros(rhs_sig)};
+    rhs_sig = rhs_zeros.trimmed_number;
+    rhs_exp += static_cast<std::int32_t>(rhs_zeros.number_of_removed_zeros);
     auto unsigned_sig_rhs {detail::make_positive_unsigned(rhs_sig)};
     auto rhs_components {detail::decimal128_components{unsigned_sig_rhs, rhs_exp, (rhs < 0)}};
 
@@ -2433,25 +2423,17 @@ constexpr auto fmad128(decimal128 x, decimal128 y, decimal128 z) noexcept -> dec
 
     auto sig_lhs {x.full_significand()};
     auto exp_lhs {x.biased_exponent()};
-
-    while (sig_lhs % 10 == 0 && sig_lhs != 0)
-    {
-        sig_lhs /= 10;
-        ++exp_lhs;
-    }
+    detail::normalize<decimal128>(sig_lhs, exp_lhs);
 
     auto sig_rhs {y.full_significand()};
     auto exp_rhs {y.biased_exponent()};
-
-    while (sig_rhs % 10 == 0 && sig_rhs != 0)
-    {
-        sig_rhs /= 10;
-        ++exp_rhs;
-    }
+    detail::normalize<decimal128>(sig_rhs, exp_rhs);
 
     auto mul_result {d128_mul_impl(sig_lhs, exp_lhs, x.isneg(), sig_rhs, exp_rhs, y.isneg())};
     const decimal128 dec_result {mul_result.sig, mul_result.exp, mul_result.sign};
 
+    return dec_result + z;
+
     const auto res_add {detail::check_non_finite(dec_result, z)};
     if (res_add != zero)
     {