From: Jonathan Wakely <jwakely@redhat.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: [PATCH] libstdc++: Optimize std::is_trivially_destructible_v
Date: Thu, 14 Dec 2023 01:07:32 +0000 [thread overview]
Message-ID: <20231214010904.1724915-1-jwakely@redhat.com> (raw)
Tested x86_64-linux.
Does this look right? Can we do it faster, or simplify it?
-- >8 --
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.
---
libstdc++-v3/include/std/type_traits | 19 +++++++++
.../is_trivially_destructible/value_v.cc | 40 +++++++++++++++++++
2 files changed, 59 insertions(+)
create mode 100644 libstdc++-v3/testsuite/20_util/is_trivially_destructible/value_v.cc
diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 677cd934b94..a0821347676 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -3300,9 +3300,28 @@ 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...);
diff --git a/libstdc++-v3/testsuite/20_util/is_trivially_destructible/value_v.cc b/libstdc++-v3/testsuite/20_util/is_trivially_destructible/value_v.cc
new file mode 100644
index 00000000000..7db098a2c4d
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/is_trivially_destructible/value_v.cc
@@ -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>();
+}
--
2.43.0
next reply other threads:[~2023-12-14 1:09 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-14 1:07 Jonathan Wakely [this message]
2024-01-07 1:00 ` Jonathan Wakely
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