Tested x86_64-linux. Pushed to trunk.
-- >8 --
Thi defines a variable template for the internal __is_duration helper
trait, defines a new __is_time_point_v variable template (to be used in
a subsequent commit), and adds explicit specializations of the standard
chrono::treat_as_floating_point trait for common types.
A fast path is added to chrono::duration_cast for the no-op case where
no conversion is needed.
Finally, some SFINAE constraints are simplified by using the
__enable_if_t alias, or by using variable templates.
libstdc++-v3/ChangeLog:
* include/bits/chrono.h (__is_duration_v, __is_time_point_v):
New variable templates.
(duration_cast): Add simplified definition for noconv case.
(treat_as_floating_point_v): Add explicit specializations.
(duration::operator%=, floor, ceil, round): Simplify SFINAE
constraints.
---
libstdc++-v3/include/bits/chrono.h | 62 ++++++++++++++++++++++--------
1 file changed, 45 insertions(+), 17 deletions(-)
diff --git a/libstdc++-v3/include/bits/chrono.h
b/libstdc++-v3/include/bits/chrono.h
index 22c0be3fbe6..56751d1c3a0 100644
--- a/libstdc++-v3/include/bits/chrono.h
+++ b/libstdc++-v3/include/bits/chrono.h
@@ -244,6 +244,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using __disable_if_is_duration
= typename enable_if<!__is_duration<_Tp>::value, _Tp>::type;
+#if __cpp_variable_templates
+ template<typename _Tp>
+ inline constexpr bool __is_duration_v = false;
+ template<typename _Rep, typename _Period>
+ inline constexpr bool __is_duration_v<duration<_Rep, _Period>> = true;
+ template<typename _Tp>
+ inline constexpr bool __is_time_point_v = false;
+ template<typename _Clock, typename _Dur>
+ inline constexpr bool __is_time_point_v<time_point<_Clock, _Dur>> = true;
+#endif
+
/// @endcond
/** Convert a `duration` to type `ToDur`.
@@ -261,13 +272,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr __enable_if_is_duration<_ToDur>
duration_cast(const duration<_Rep, _Period>& __d)
{
- typedef typename _ToDur::period __to_period;
- typedef typename _ToDur::rep __to_rep;
- typedef ratio_divide<_Period, __to_period> __cf;
- typedef typename common_type<__to_rep, _Rep, intmax_t>::type __cr;
- typedef __duration_cast_impl<_ToDur, __cf, __cr,
- __cf::num == 1, __cf::den == 1> __dc;
- return __dc::__cast(__d);
+#if __cpp_inline_variables && __cpp_if_constexpr
+ if constexpr (is_same_v<_ToDur, duration<_Rep, _Period>>)
+ return __d;
+ else
+#endif
+ {
+ using __to_period = typename _ToDur::period;
+ using __to_rep = typename _ToDur::rep;
+ using __cf = ratio_divide<_Period, __to_period>;
+ using __cr = typename common_type<__to_rep, _Rep, intmax_t>::type;
+ using __dc = __duration_cast_impl<_ToDur, __cf, __cr,
+ __cf::num == 1, __cf::den == 1>;
+ return __dc::__cast(__d);
+ }
}
/** Trait indicating whether to treat a type as a floating-point type.
@@ -290,6 +308,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template <typename _Rep>
inline constexpr bool treat_as_floating_point_v =
treat_as_floating_point<_Rep>::value;
+
+ template<>
+ inline constexpr bool treat_as_floating_point_v<int> = false;
+ template<>
+ inline constexpr bool treat_as_floating_point_v<long> = false;
+ template<>
+ inline constexpr bool treat_as_floating_point_v<long long> = false;
+ template<>
+ inline constexpr bool treat_as_floating_point_v<float> = true;
+ template<>
+ inline constexpr bool treat_as_floating_point_v<double> = true;
+ template<>
+ inline constexpr bool treat_as_floating_point_v<long double> = true;
#endif // C++17
#if __cplusplus > 201703L
@@ -632,8 +663,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// DR 934.
template<typename _Rep2 = rep>
_GLIBCXX17_CONSTEXPR
- typename enable_if<!treat_as_floating_point<_Rep2>::value,
- duration&>::type
+ __enable_if_t<!treat_as_floating_point<_Rep2>::value, duration&>
operator%=(const rep& __rhs)
{
__r %= __rhs;
@@ -642,8 +672,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Rep2 = rep>
_GLIBCXX17_CONSTEXPR
- typename enable_if<!treat_as_floating_point<_Rep2>::value,
- duration&>::type
+ __enable_if_t<!treat_as_floating_point<_Rep2>::value, duration&>
operator%=(const duration& __d)
{
__r %= __d.count();
@@ -1019,7 +1048,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*/
template<typename _ToDur, typename _Clock, typename _Dur>
[[nodiscard]] constexpr
- enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
+ enable_if_t<__is_duration_v<_ToDur>, time_point<_Clock, _ToDur>>
floor(const time_point<_Clock, _Dur>& __tp)
{
return time_point<_Clock, _ToDur>{
@@ -1040,7 +1069,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*/
template<typename _ToDur, typename _Clock, typename _Dur>
[[nodiscard]] constexpr
- enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
+ enable_if_t<__is_duration_v<_ToDur>, time_point<_Clock, _ToDur>>
ceil(const time_point<_Clock, _Dur>& __tp)
{
return time_point<_Clock, _ToDur>{
@@ -1062,10 +1091,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*/
template<typename _ToDur, typename _Clock, typename _Dur>
[[nodiscard]] constexpr
- enable_if_t<
- __and_<__is_duration<_ToDur>,
- __not_<treat_as_floating_point<typename _ToDur::rep>>>::value,
- time_point<_Clock, _ToDur>>
+ enable_if_t<__is_duration_v<_ToDur>
+ && !treat_as_floating_point_v<typename _ToDur::rep>,
+ time_point<_Clock, _ToDur>>
round(const time_point<_Clock, _Dur>& __tp)
{
return time_point<_Clock, _ToDur>{
--
2.38.1
