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| author | Jonathan Wakely <jwakely@redhat.com> | 2019-06-24 13:09:51 +0100 |
|---|---|---|
| committer | Jonathan Wakely <redi@gcc.gnu.org> | 2019-06-24 13:09:51 +0100 |
| commit | a3c8d7fbe29d4ab60cc46196a1376854734a4f8d (patch) | |
| tree | 5443500477c03424be3f577a036c328b5802073c /libstdc++-v3/include/std | |
| parent | ff164b601b75a9aba47edfaa9a215cb376ab055e (diff) | |
| download | gcc-a3c8d7fbe29d4ab60cc46196a1376854734a4f8d.zip gcc-a3c8d7fbe29d4ab60cc46196a1376854734a4f8d.tar.gz gcc-a3c8d7fbe29d4ab60cc46196a1376854734a4f8d.tar.bz2 | |
Fix std::midpoint for denormal values
* include/std/numeric (midpoint(T, T)): Change implementation for
floating-point types to avoid incorrect rounding of denormals.
* testsuite/26_numerics/midpoint/floating.cc: Add check for correct
rounding with denormals.
* testsuite/26_numerics/gcd/gcd_neg.cc: Adjust dg-error line numbers.
* testsuite/26_numerics/lcm/lcm_neg.cc: Likewise.
From-SVN: r272616
Diffstat (limited to 'libstdc++-v3/include/std')
| -rw-r--r-- | libstdc++-v3/include/std/numeric | 36 |
1 files changed, 25 insertions, 11 deletions
diff --git a/libstdc++-v3/include/std/numeric b/libstdc++-v3/include/std/numeric index fc2242f..af68446 100644 --- a/libstdc++-v3/include/std/numeric +++ b/libstdc++-v3/include/std/numeric @@ -69,9 +69,8 @@ * @defgroup numerics Numerics * * Components for performing numeric operations. Includes support for - * for complex number types, random number generation, numeric - * (n-at-a-time) arrays, generalized numeric algorithms, and special - * math functions. + * complex number types, random number generation, numeric (n-at-a-time) + * arrays, generalized numeric algorithms, and mathematical special functions. */ #if __cplusplus >= 201402L @@ -156,11 +155,22 @@ namespace __detail #endif // C++17 +_GLIBCXX_END_NAMESPACE_VERSION +} // namespace std + +#endif // C++14 + #if __cplusplus > 201703L +#include <limits> +#include <bits/std_abs.h> + +namespace std _GLIBCXX_VISIBILITY(default) +{ +_GLIBCXX_BEGIN_NAMESPACE_VERSION // midpoint # define __cpp_lib_interpolate 201902L -template<typename _Tp> + template<typename _Tp> constexpr enable_if_t<__and_v<is_arithmetic<_Tp>, is_same<remove_cv_t<_Tp>, _Tp>, __not_<is_same<_Tp, bool>>>, @@ -182,11 +192,17 @@ template<typename _Tp> } return __a + __k * _Tp(_Up(__M - __m) / 2); } - else + else // is_floating { - return __builtin_isnormal(__a) && __builtin_isnormal(__b) - ? __a / 2 + __b / 2 - : (__a + __b) / 2; + constexpr _Tp __lo = numeric_limits<_Tp>::min() * 2; + constexpr _Tp __hi = numeric_limits<_Tp>::max() / 2; + if (std::abs(__a) <= __hi && std::abs(__b) <= __hi) [[likely]] + return (__a + __b) / 2; // always correctly rounded + if (std::abs(__a) < __lo) // not safe to halve __a + return __a + __b/2; + if (std::abs(__b) < __lo) // not safe to halve __b + return __a/2 + __b; + return __a/2 + __b/2; // otherwise correctly rounded } } @@ -197,12 +213,10 @@ template<typename _Tp> { return __a + (__b - __a) / 2; } -#endif // C++20 - _GLIBCXX_END_NAMESPACE_VERSION } // namespace std -#endif // C++14 +#endif // C++20 #if __cplusplus > 201402L #include <bits/stl_function.h> |