Merge pull request #1125 from cppalliance/1111

Avoid double counting digits in normalization process

Author: mborland

include/boost/decimal/decimal128_t.hpp

@@ -728,7 +728,7 @@ constexpr decimal128_t::decimal128_t(T1 coeff, T2 exp, bool sign) noexcept
     {
         if (coeff > detail::d128_max_significand_value || biased_exp < 0)
         {
-            coeff_digits = detail::coefficient_rounding<decimal128_t>(coeff, exp, biased_exp, sign);
+            coeff_digits = detail::coefficient_rounding<decimal128_t>(coeff, exp, biased_exp, sign, detail::num_digits(coeff));
         }
     }
 

include/boost/decimal/decimal32_t.hpp

@@ -635,7 +635,7 @@ constexpr decimal32_t::decimal32_t(T1 coeff, T2 exp, bool sign) noexcept // NOLI
     auto biased_exp {static_cast<int>(exp + detail::bias)};
     if (coeff > detail::d32_max_significand_value || biased_exp < 0)
     {
-        coeff_digits = detail::coefficient_rounding<decimal32_t>(coeff, exp, biased_exp, sign);
+        coeff_digits = detail::coefficient_rounding<decimal32_t>(coeff, exp, biased_exp, sign, detail::num_digits(coeff));
     }
 
     auto reduced_coeff {static_cast<significand_type>(coeff)};

include/boost/decimal/decimal64_t.hpp

@@ -629,7 +629,7 @@ constexpr decimal64_t::decimal64_t(T1 coeff, T2 exp, bool sign) noexcept
     auto biased_exp {static_cast<int>(exp) + detail::bias_v<decimal64_t>};
     if (coeff > detail::d64_max_significand_value || biased_exp < 0)
     {
-        coeff_digits = detail::coefficient_rounding<decimal64_t>(coeff, exp, biased_exp, sign);
+        coeff_digits = detail::coefficient_rounding<decimal64_t>(coeff, exp, biased_exp, sign, detail::num_digits(coeff));
     }
 
     auto reduced_coeff {static_cast<significand_type>(coeff)};

include/boost/decimal/detail/fenv_rounding.hpp

@@ -182,14 +182,12 @@ constexpr auto fenv_round(T& val, bool is_neg = false, bool sticky = false) noex
 #endif
 
 template <typename TargetDecimalType, typename T1, typename T2, typename T3>
-constexpr auto coefficient_rounding(T1& coeff, T2& exp, T3& biased_exp, const bool sign) noexcept
+constexpr auto coefficient_rounding(T1& coeff, T2& exp, T3& biased_exp, const bool sign, int coeff_digits) noexcept
 {
     // T1 will be a 128-bit or 256-bit
     using sig_type = typename TargetDecimalType::significand_type;
     using demoted_integer_type = std::conditional_t<std::numeric_limits<T1>::digits10 < std::numeric_limits<sig_type>::digits10, T1, sig_type>;
 
-    auto coeff_digits {detail::num_digits(coeff)};
-
     // How many digits need to be shifted?
     const auto shift_for_large_coeff {(coeff_digits - detail::precision_v<TargetDecimalType>) - 1};
     int shift {};

include/boost/decimal/detail/normalize.hpp

@@ -31,7 +31,7 @@ constexpr auto normalize(T1& significand, T2& exp, bool sign = false) noexcept -
     else if (digits > target_precision)
     {
         auto biased_exp {static_cast<int>(exp) + detail::bias_v<TargetDecimalType>};
-        detail::coefficient_rounding<TargetDecimalType>(significand, exp, biased_exp, sign);
+        detail::coefficient_rounding<TargetDecimalType>(significand, exp, biased_exp, sign, digits);
     }
 }