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libstdc++: Optimize std::is_trivially_destructible_v

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This reduces the overhead of using std::is_trivially_destructible_v and
as a result fixes some recent regressions seen with a non-default
GLIBCXX_TESTSUITE_STDS env var:
FAIL: 20_util/variant/87619.cc  -std=gnu++20 (test for excess errors)
FAIL: 20_util/variant/87619.cc  -std=gnu++23 (test for excess errors)
FAIL: 20_util/variant/87619.cc  -std=gnu++26 (test for excess errors)

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_trivially_destructible_v): Use
	built-in directly when concepts are supported.
	* testsuite/20_util/is_trivially_destructible/value_v.cc: New
	test.
This commit is contained in:
Jonathan Wakely 2023-11-22 15:09:24 +00:00
parent b368d79998
commit 7af436ada2
2 changed files with 59 additions and 0 deletions
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19
libstdc++-v3/include/std/type_traits
View file

@ -3410,9 +3410,28 @@ template <typename _Tp>
inline constexpr bool is_trivially_move_assignable_v
= __is_trivially_assignable(__add_lval_ref_t<_Tp>,
__add_rval_ref_t<_Tp>);
#if __cpp_concepts
template <typename _Tp>
inline constexpr bool is_trivially_destructible_v = false;
template <typename _Tp>
requires (!is_reference_v<_Tp>) && requires (_Tp& __t) { __t.~_Tp(); }
inline constexpr bool is_trivially_destructible_v<_Tp>
= __has_trivial_destructor(_Tp);
template <typename _Tp>
inline constexpr bool is_trivially_destructible_v<_Tp&> = true;
template <typename _Tp>
inline constexpr bool is_trivially_destructible_v<_Tp&&> = true;
template <typename _Tp, size_t _Nm>
inline constexpr bool is_trivially_destructible_v<_Tp[_Nm]>
= is_trivially_destructible_v<_Tp>;
#else
template <typename _Tp>
inline constexpr bool is_trivially_destructible_v =
is_trivially_destructible<_Tp>::value;
#endif
template <typename _Tp, typename... _Args>
inline constexpr bool is_nothrow_constructible_v
= __is_nothrow_constructible(_Tp, _Args...);

40
libstdc++-v3/testsuite/20_util/is_trivially_destructible/value_v.cc Normal file
View file

@ -0,0 +1,40 @@
// { dg-do compile { target c++17 } }
#include <type_traits>
#include <testsuite_tr1.h>
template<typename T>
constexpr void test_cv()
{
static_assert(std::is_trivially_destructible_v<const T>
== std::is_trivially_destructible_v<T>);
static_assert(std::is_trivially_destructible_v<volatile T>
== std::is_trivially_destructible_v<T>);
static_assert(std::is_trivially_destructible_v<const volatile T>
== std::is_trivially_destructible_v<T>);
}
template<typename T, bool Expected>
void test()
{
static_assert(std::is_trivially_destructible_v<T> == Expected);
test_cv<T>();
}
void test01()
{
using namespace __gnu_test;
test<int, true>();
test<int&, true>();
test<int&&, true>();
test<int[1], true>();
test<TType, true>();
test<TType[1], true>();
test<PODType, true>();
test<PODType[1], true>();
test<NType, false>();
test<SLType, false>();
test<int(), false>();
test<void, false>();
test<int[], false>();
}