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libstdc++: Simplify std::common_comparison_category 

* libsupc++/compare (common_comparison_category): Define without using
	concepts and optimise for compilation time.
	(__detail::__cmp_cat_ids): Remove.
	(__detail::__common_cmp_cat): Replace class template and
	specializations with constexpr function.

From-SVN: r279307
This commit is contained in:
Jonathan Wakely 2019-12-12 14:35:55 +00:00 committed by Jonathan Wakely
parent 2fb1d6d654
commit d1505d0146
2 changed files with 30 additions and 31 deletions
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8
libstdc++-v3/ChangeLog
View File

@ -1,3 +1,11 @@
2019-12-12 Jonathan Wakely <jwakely@redhat.com>
* libsupc++/compare (common_comparison_category): Define without using
concepts and optimise for compilation time.
(__detail::__cmp_cat_ids): Remove.
(__detail::__common_cmp_cat): Replace class template and
specializations with constexpr function.
2019-12-12 François Dumont <fdumont@gcc.gnu.org>
* include/tr1/cctype: Add _GLIBCXX_BEGIN_VERSION_NAMESPACE and

53
libstdc++-v3/libsupc++/compare
View File

@ -385,53 +385,43 @@ namespace std
is_gteq(partial_ordering __cmp) noexcept
{ return __cmp >= 0; }
#if __cpp_lib_concepts
namespace __detail
{
template<typename _Tp>
inline constexpr unsigned __cmp_cat_id = 1;
template<>
inline constexpr unsigned __cmp_cat_id<strong_ordering> = 2;
inline constexpr unsigned __cmp_cat_id<partial_ordering> = 2;
template<>
inline constexpr unsigned __cmp_cat_id<weak_ordering> = 4;
template<>
inline constexpr unsigned __cmp_cat_id<partial_ordering> = 8;
inline constexpr unsigned __cmp_cat_id<strong_ordering> = 8;
template<typename... _Ts>
constexpr unsigned __cmp_cat_ids()
{ return (__cmp_cat_id<_Ts> | ...); }
template<unsigned>
struct __common_cmp_cat;
// If any Ti is not a comparison category type, U is void.
template<unsigned _Bits>
requires ((_Bits & 1) == 1)
struct __common_cmp_cat<_Bits> { using type = void; };
// Otherwise, if at least one Ti is std::partial_ordering,
// U is std::partial_ordering.
template<unsigned _Bits>
requires ((_Bits & 0b1001) == 0b1000)
struct __common_cmp_cat<_Bits> { using type = partial_ordering; };
// Otherwise, if at least one Ti is std::weak_ordering,
// U is std::weak_ordering.
template<unsigned _Bits>
requires ((_Bits & 0b1101) == 0b0100)
struct __common_cmp_cat<_Bits> { using type = weak_ordering; };
// Otherwise, U is std::strong_ordering.
template<>
struct __common_cmp_cat<0b0010> { using type = strong_ordering; };
constexpr auto __common_cmp_cat()
{
constexpr unsigned __cats = (__cmp_cat_id<_Ts> | ...);
// If any Ti is not a comparison category type, U is void.
if constexpr (__cats & 1)
return;
// Otherwise, if at least one Ti is std::partial_ordering,
// U is std::partial_ordering.
else if constexpr (bool(__cats & __cmp_cat_id<partial_ordering>))
return partial_ordering::equivalent;
// Otherwise, if at least one Ti is std::weak_ordering,
// U is std::weak_ordering.
else if constexpr (bool(__cats & __cmp_cat_id<weak_ordering>))
return weak_ordering::equivalent;
// Otherwise, U is std::strong_ordering.
else
return strong_ordering::equivalent;
}
} // namespace __detail
// [cmp.common], common comparison category type
template<typename... _Ts>
struct common_comparison_category
{
using type
= __detail::__common_cmp_cat<__detail::__cmp_cat_ids<_Ts...>()>::type;
using type = decltype(__detail::__common_cmp_cat<_Ts...>());
};
// Partial specializations for one and zero argument cases.
@ -460,6 +450,7 @@ namespace std
using common_comparison_category_t
= typename common_comparison_category<_Ts...>::type;
#if __cpp_lib_concepts
namespace __detail
{
template<typename _Tp, typename _Cat>