[libcxx-commits] [libcxx] [libc++] Optimize vector growing of trivially relocatable types (PR #76657)
Nikolas Klauser via libcxx-commits
libcxx-commits at lists.llvm.org
Fri Jan 12 04:58:53 PST 2024
https://github.com/philnik777 updated https://github.com/llvm/llvm-project/pull/76657
>From 0869709d4bdd8d522ebab154caa70c108eb65d83 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Sun, 31 Dec 2023 13:35:00 +0100
Subject: [PATCH] [libc++] Optimize vector growing of trivially relocatable
types
---
libcxx/benchmarks/ContainerBenchmarks.h | 2 +-
libcxx/benchmarks/vector_operations.bench.cpp | 18 +++-
libcxx/docs/ReleaseNotes/18.rst | 2 +
libcxx/include/CMakeLists.txt | 1 +
libcxx/include/__fwd/string.h | 2 +
.../__memory/uninitialized_algorithms.h | 77 ++++++--------
libcxx/include/__memory/unique_ptr.h | 23 ++++
.../__type_traits/is_trivially_relocatable.h | 39 +++++++
libcxx/include/string | 14 +++
libcxx/include/vector | 39 +++++--
.../is_trivially_comparable.compile.pass.cpp | 10 +-
.../is_trivially_relocatable.compile.pass.cpp | 100 ++++++++++++++++++
12 files changed, 265 insertions(+), 62 deletions(-)
create mode 100644 libcxx/include/__type_traits/is_trivially_relocatable.h
create mode 100644 libcxx/test/libcxx/type_traits/is_trivially_relocatable.compile.pass.cpp
diff --git a/libcxx/benchmarks/ContainerBenchmarks.h b/libcxx/benchmarks/ContainerBenchmarks.h
index 9a9abfd3b0d0f6..744505b439985b 100644
--- a/libcxx/benchmarks/ContainerBenchmarks.h
+++ b/libcxx/benchmarks/ContainerBenchmarks.h
@@ -80,7 +80,7 @@ void BM_ConstructFromRange(benchmark::State& st, Container, GenInputs gen) {
}
template <class Container>
-void BM_Pushback(benchmark::State& state, Container c) {
+void BM_Pushback_no_grow(benchmark::State& state, Container c) {
int count = state.range(0);
c.reserve(count);
while (state.KeepRunningBatch(count)) {
diff --git a/libcxx/benchmarks/vector_operations.bench.cpp b/libcxx/benchmarks/vector_operations.bench.cpp
index 38b14c56756fba..da21d1806c0129 100644
--- a/libcxx/benchmarks/vector_operations.bench.cpp
+++ b/libcxx/benchmarks/vector_operations.bench.cpp
@@ -1,6 +1,7 @@
#include <cstdint>
#include <cstdlib>
#include <cstring>
+#include <deque>
#include <functional>
#include <vector>
@@ -39,6 +40,21 @@ BENCHMARK_CAPTURE(BM_ConstructFromRange, vector_size_t, std::vector<size_t>{}, g
BENCHMARK_CAPTURE(BM_ConstructFromRange, vector_string, std::vector<std::string>{}, getRandomStringInputs)
->Arg(TestNumInputs);
-BENCHMARK_CAPTURE(BM_Pushback, vector_int, std::vector<int>{})->Arg(TestNumInputs);
+BENCHMARK_CAPTURE(BM_Pushback_no_grow, vector_int, std::vector<int>{})->Arg(TestNumInputs);
+
+template <class T>
+void bm_grow(benchmark::State& state) {
+ for (auto _ : state) {
+ std::vector<T> vec;
+ benchmark::DoNotOptimize(vec);
+ for (size_t i = 0; i != 2048; ++i)
+ vec.emplace_back();
+ benchmark::DoNotOptimize(vec);
+ }
+}
+BENCHMARK(bm_grow<int>);
+BENCHMARK(bm_grow<std::string>);
+BENCHMARK(bm_grow<std::unique_ptr<int>>);
+BENCHMARK(bm_grow<std::deque<int>>);
BENCHMARK_MAIN();
diff --git a/libcxx/docs/ReleaseNotes/18.rst b/libcxx/docs/ReleaseNotes/18.rst
index fa60a581652d6a..412140bf2bdbce 100644
--- a/libcxx/docs/ReleaseNotes/18.rst
+++ b/libcxx/docs/ReleaseNotes/18.rst
@@ -69,6 +69,8 @@ Improvements and New Features
- ``std::for_each`` has been optimized for segmented iterators like ``std::deque::iterator`` in C++23 and
later, which can lead up to 40x performance improvements.
+- The performance of growing ``std::vector`` has been improved for trivially relocatable types.
+
- The library now provides several hardening modes under which common cases of library undefined behavior will be turned
into a reliable program termination. The ``fast`` hardening mode enables a set of security-critical checks with
minimal runtime overhead; the ``extensive`` hardening mode additionally enables relatively cheap checks that catch
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 0fe3ab44d2466e..d0436aeda3d157 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -803,6 +803,7 @@ set(files
__type_traits/is_trivially_lexicographically_comparable.h
__type_traits/is_trivially_move_assignable.h
__type_traits/is_trivially_move_constructible.h
+ __type_traits/is_trivially_relocatable.h
__type_traits/is_unbounded_array.h
__type_traits/is_union.h
__type_traits/is_unsigned.h
diff --git a/libcxx/include/__fwd/string.h b/libcxx/include/__fwd/string.h
index 032132374de5ed..a0a94241d72dee 100644
--- a/libcxx/include/__fwd/string.h
+++ b/libcxx/include/__fwd/string.h
@@ -12,6 +12,8 @@
#include <__availability>
#include <__config>
#include <__fwd/memory_resource.h>
+#include <__type_traits/is_fundamental.h>
+#include <__type_traits/is_trivially_relocatable.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
diff --git a/libcxx/include/__memory/uninitialized_algorithms.h b/libcxx/include/__memory/uninitialized_algorithms.h
index 2a4ecf655be287..723c095267ba30 100644
--- a/libcxx/include/__memory/uninitialized_algorithms.h
+++ b/libcxx/include/__memory/uninitialized_algorithms.h
@@ -29,6 +29,7 @@
#include <__type_traits/is_trivially_copy_constructible.h>
#include <__type_traits/is_trivially_move_assignable.h>
#include <__type_traits/is_trivially_move_constructible.h>
+#include <__type_traits/is_trivially_relocatable.h>
#include <__type_traits/is_unbounded_array.h>
#include <__type_traits/negation.h>
#include <__type_traits/remove_const.h>
@@ -591,60 +592,48 @@ __uninitialized_allocator_copy(_Alloc& __alloc, _Iter1 __first1, _Sent1 __last1,
return std::__rewrap_iter(__first2, __result);
}
-// Move-construct the elements [__first1, __last1) into [__first2, __first2 + N)
-// if the move constructor is noexcept, where N is distance(__first1, __last1).
-//
-// Otherwise try to copy all elements. If an exception is thrown the already copied
-// elements are destroyed in reverse order of their construction.
-template <class _Alloc, class _Iter1, class _Sent1, class _Iter2>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Iter2
-__uninitialized_allocator_move_if_noexcept(_Alloc& __alloc, _Iter1 __first1, _Sent1 __last1, _Iter2 __first2) {
- static_assert(__is_cpp17_move_insertable<_Alloc>::value,
- "The specified type does not meet the requirements of Cpp17MoveInsertable");
- auto __destruct_first = __first2;
- auto __guard =
- std::__make_exception_guard(_AllocatorDestroyRangeReverse<_Alloc, _Iter2>(__alloc, __destruct_first, __first2));
- while (__first1 != __last1) {
-#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
- allocator_traits<_Alloc>::construct(__alloc, std::__to_address(__first2), std::move_if_noexcept(*__first1));
-#else
- allocator_traits<_Alloc>::construct(__alloc, std::__to_address(__first2), std::move(*__first1));
-#endif
- ++__first1;
- ++__first2;
- }
- __guard.__complete();
- return __first2;
-}
-
template <class _Alloc, class _Type>
struct __allocator_has_trivial_move_construct : _Not<__has_construct<_Alloc, _Type*, _Type&&> > {};
template <class _Type>
struct __allocator_has_trivial_move_construct<allocator<_Type>, _Type> : true_type {};
-#ifndef _LIBCPP_COMPILER_GCC
-template <
- class _Alloc,
- class _Iter1,
- class _Iter2,
- class _Type = typename iterator_traits<_Iter1>::value_type,
- class = __enable_if_t<is_trivially_move_constructible<_Type>::value && is_trivially_move_assignable<_Type>::value &&
- __allocator_has_trivial_move_construct<_Alloc, _Type>::value> >
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Iter2
-__uninitialized_allocator_move_if_noexcept(_Alloc&, _Iter1 __first1, _Iter1 __last1, _Iter2 __first2) {
- if (__libcpp_is_constant_evaluated()) {
- while (__first1 != __last1) {
- std::__construct_at(std::__to_address(__first2), std::move(*__first1));
- ++__first1;
- ++__first2;
+template <class _Alloc, class _Tp>
+struct __allocator_has_trivial_destroy : _Not<__has_destroy<_Alloc, _Tp*>> {};
+
+template <class _Tp, class _Up>
+struct __allocator_has_trivial_destroy<allocator<_Tp>, _Up> : true_type {};
+
+// __uninitialized_allocator_relocate relocates the objects in [__first, __last) into __result.
+// relocation means that the objects in [__first, __last) are placed into __result as-if by move-construct and destroy,
+// except that the move constructor and destructor may never be called if they are known to be equivalent to a memcpy.
+//
+// Preconditions: __result doesn't contain any objects and [__first, __last) contains objects
+// Postconditions: __result contains the object from [__first, __last) and [__first, __last) doesn't contain any objects
+template <class _Alloc, class _Tp>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
+__uninitialized_allocator_relocate(_Alloc& __alloc, _Tp* __first, _Tp* __last, _Tp* __result) {
+ if (__libcpp_is_constant_evaluated() || !__libcpp_is_trivially_relocatable<_Tp>::value ||
+ !__allocator_has_trivial_move_construct<_Alloc, _Tp>::value ||
+ !__allocator_has_trivial_destroy<_Alloc, _Tp>::value) {
+ auto __destruct_first = __result;
+ auto __guard =
+ std::__make_exception_guard(_AllocatorDestroyRangeReverse<_Alloc, _Tp*>(__alloc, __destruct_first, __result));
+ while (__first != __last) {
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+ allocator_traits<_Alloc>::construct(__alloc, std::__to_address(__result), std::move_if_noexcept(*__first));
+#else
+ allocator_traits<_Alloc>::construct(__alloc, std::__to_address(__result), std::move(*__first));
+#endif
+ ++__first;
+ ++__result;
}
- return __first2;
+ __guard.__complete();
+ std::__allocator_destroy(__alloc, __first, __last);
} else {
- return std::move(__first1, __last1, __first2);
+ __builtin_memcpy(__result, __first, sizeof(_Tp) * (__last - __first));
}
}
-#endif // _LIBCPP_COMPILER_GCC
_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__memory/unique_ptr.h b/libcxx/include/__memory/unique_ptr.h
index 7bf5e3c5e4e6b5..e68c0625a4c2de 100644
--- a/libcxx/include/__memory/unique_ptr.h
+++ b/libcxx/include/__memory/unique_ptr.h
@@ -33,6 +33,7 @@
#include <__type_traits/is_reference.h>
#include <__type_traits/is_same.h>
#include <__type_traits/is_swappable.h>
+#include <__type_traits/is_trivially_relocatable.h>
#include <__type_traits/is_void.h>
#include <__type_traits/remove_extent.h>
#include <__type_traits/type_identity.h>
@@ -129,6 +130,17 @@ class _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS unique_ptr {
static_assert(!is_rvalue_reference<deleter_type>::value, "the specified deleter type cannot be an rvalue reference");
+ // A unique_ptr contains the following members which may be trivially relocatable:
+ // - pointer : this may be trivially relocatable, so it's checked
+ // - delter_type: this may be trivially relocatable, so it's checked
+ //
+ // This uniuqe_ptr implementation only contains a pointer to the unique object and a delter, so there are no
+ // references to itself. This means that the entire structure is trivially relocatable if it's members are.
+ using __trivially_relocatable = __conditional_t<
+ __libcpp_is_trivially_relocatable<pointer>::value && __libcpp_is_trivially_relocatable<deleter_type>::value,
+ unique_ptr,
+ void>;
+
private:
__compressed_pair<pointer, deleter_type> __ptr_;
@@ -280,6 +292,17 @@ class _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS unique_ptr<_Tp[], _Dp>
typedef _Dp deleter_type;
typedef typename __pointer<_Tp, deleter_type>::type pointer;
+ // A unique_ptr contains the following members which may be trivially relocatable:
+ // - pointer : this may be trivially relocatable, so it's checked
+ // - delter_type: this may be trivially relocatable, so it's checked
+ //
+ // This uniuqe_ptr implementation only contains a pointer to the unique object and a delter, so there are no
+ // references to itself. This means that the entire structure is trivially relocatable if it's members are.
+ using __trivially_relocatable = __conditional_t<
+ __libcpp_is_trivially_relocatable<pointer>::value && __libcpp_is_trivially_relocatable<deleter_type>::value,
+ unique_ptr,
+ void>;
+
private:
__compressed_pair<pointer, deleter_type> __ptr_;
diff --git a/libcxx/include/__type_traits/is_trivially_relocatable.h b/libcxx/include/__type_traits/is_trivially_relocatable.h
new file mode 100644
index 00000000000000..af058759236c24
--- /dev/null
+++ b/libcxx/include/__type_traits/is_trivially_relocatable.h
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___TYPE_TRAITS_IS_TRIVIALLY_RELOCATABLE_H
+#define _LIBCPP___TYPE_TRAITS_IS_TRIVIALLY_RELOCATABLE_H
+
+#include <__config>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/integral_constant.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/is_trivially_copyable.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if __has_builtin(__is_trivially_relocatable)
+template <class _Tp, class = void>
+struct __libcpp_is_trivially_relocatable : integral_constant<bool, __is_trivially_relocatable(_Tp)> {};
+#else
+template <class _Tp, class = void>
+struct __libcpp_is_trivially_relocatable : is_trivially_copyable<_Tp> {};
+#endif
+
+template <class _Tp>
+struct __libcpp_is_trivially_relocatable<_Tp,
+ __enable_if_t<is_same<_Tp, typename _Tp::__trivially_relocatable>::value> >
+ : true_type {};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TYPE_TRAITS_IS_TRIVIALLY_RELOCATABLE_H
diff --git a/libcxx/include/string b/libcxx/include/string
index c676182fba8bac..0dba9c51b65458 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -724,6 +724,20 @@ public:
typedef typename __alloc_traits::pointer pointer;
typedef typename __alloc_traits::const_pointer const_pointer;
+ // A basic_string contains the following members which may be trivially relocatable:
+ // - pointer: is currently assumed to be trivially relocatable, but is still checked in case that changes
+ // - size_type: is always trivially relocatable, since it has to be an integral type
+ // - value_type: is always trivially relocatable, since it has to be trivial
+ // - unsigned char: is a fundamental type, so it's trivially relocatable
+ // - allocator_type: may or may not be trivially relocatable, so it's checked
+ //
+ // This string implementation doesn't contain any references into itself. It only contains a bit that says whether
+ // it is in small or large string mode, so the entire structure is trivially relocatable if it's members are.
+ using __trivially_relocatable = __conditional_t<
+ __libcpp_is_trivially_relocatable<allocator_type>::value && __libcpp_is_trivially_relocatable<pointer>::value,
+ basic_string,
+ void>;
+
static_assert((!is_array<value_type>::value), "Character type of basic_string must not be an array");
static_assert((is_standard_layout<value_type>::value), "Character type of basic_string must be standard-layout");
static_assert((is_trivial<value_type>::value), "Character type of basic_string must be trivial");
diff --git a/libcxx/include/vector b/libcxx/include/vector
index 0098273a195ff8..1e368fdcb8d3dd 100644
--- a/libcxx/include/vector
+++ b/libcxx/include/vector
@@ -982,14 +982,18 @@ template <ranges::input_range _Range,
vector(from_range_t, _Range&&, _Alloc = _Alloc()) -> vector<ranges::range_value_t<_Range>, _Alloc>;
#endif
+// __swap_out_circular_buffer relocates the objects in [__begin_, __end_) into the front of __v and swaps the buffers of
+// *this and __v. It is assumed that __v provides space for exactly (__end_ - __begin_) objects in the front. This
+// function has a strong exception guarantee.
template <class _Tp, class _Allocator>
_LIBCPP_CONSTEXPR_SINCE_CXX20 void
vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, allocator_type&>& __v) {
__annotate_delete();
- using _RevIter = std::reverse_iterator<pointer>;
- __v.__begin_ = std::__uninitialized_allocator_move_if_noexcept(
- __alloc(), _RevIter(__end_), _RevIter(__begin_), _RevIter(__v.__begin_))
- .base();
+ auto __new_begin = __v.__begin_ - (__end_ - __begin_);
+ std::__uninitialized_allocator_relocate(
+ __alloc(), std::__to_address(__begin_), std::__to_address(__end_), std::__to_address(__new_begin));
+ __v.__begin_ = __new_begin;
+ __end_ = __begin_; // All the objects have been destroyed by relocating them.
std::swap(this->__begin_, __v.__begin_);
std::swap(this->__end_, __v.__end_);
std::swap(this->__end_cap(), __v.__end_cap());
@@ -997,22 +1001,35 @@ vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, a
__annotate_new(size());
}
+// __swap_out_circular_buffer relocates the objects in [__begin_, __p) into the front of __v, the objects in
+// [__p, __end_) into the back of __v and swaps the buffers of *this and __v. It is assumed that __v provides space for
+// exactly (__p - __begin_) objects in the front and space for at least (__end_ - __p) objects in the back. This
+// function has a strong exception guarantee if __begin_ == __p || __end_ == __p.
template <class _Tp, class _Allocator>
_LIBCPP_CONSTEXPR_SINCE_CXX20 typename vector<_Tp, _Allocator>::pointer
vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, allocator_type&>& __v, pointer __p) {
__annotate_delete();
- pointer __r = __v.__begin_;
- using _RevIter = std::reverse_iterator<pointer>;
- __v.__begin_ = std::__uninitialized_allocator_move_if_noexcept(
- __alloc(), _RevIter(__p), _RevIter(__begin_), _RevIter(__v.__begin_))
- .base();
- __v.__end_ = std::__uninitialized_allocator_move_if_noexcept(__alloc(), __p, __end_, __v.__end_);
+ pointer __ret = __v.__begin_;
+
+ // Relocate [__p, __end_) first to avoid having a hole in [__begin_, __end_)
+ // in case something in [__begin_, __p) throws.
+ std::__uninitialized_allocator_relocate(
+ __alloc(), std::__to_address(__p), std::__to_address(__end_), std::__to_address(__v.__end_));
+ __v.__end_ += (__end_ - __p);
+ __end_ = __p; // The objects in [__p, __end_) have been destroyed by relocating them.
+ auto __new_begin = __v.__begin_ - (__p - __begin_);
+
+ std::__uninitialized_allocator_relocate(
+ __alloc(), std::__to_address(__begin_), std::__to_address(__p), std::__to_address(__new_begin));
+ __v.__begin_ = __new_begin;
+ __end_ = __begin_; // All the objects have been destroyed by relocating them.
+
std::swap(this->__begin_, __v.__begin_);
std::swap(this->__end_, __v.__end_);
std::swap(this->__end_cap(), __v.__end_cap());
__v.__first_ = __v.__begin_;
__annotate_new(size());
- return __r;
+ return __ret;
}
template <class _Tp, class _Allocator>
diff --git a/libcxx/test/libcxx/type_traits/is_trivially_comparable.compile.pass.cpp b/libcxx/test/libcxx/type_traits/is_trivially_comparable.compile.pass.cpp
index e2be399456b1bc..d33a9bf5902289 100644
--- a/libcxx/test/libcxx/type_traits/is_trivially_comparable.compile.pass.cpp
+++ b/libcxx/test/libcxx/type_traits/is_trivially_comparable.compile.pass.cpp
@@ -47,7 +47,7 @@ static_assert(std::__libcpp_is_trivially_equality_comparable<
"");
static_assert(std::__libcpp_is_trivially_equality_comparable<char16_t, std::uint_least16_t>::value, "");
-struct S {
+struct Empty {
char c;
};
@@ -55,11 +55,11 @@ struct S2 {
char c;
};
-struct VirtualBase : virtual S {};
-struct NonVirtualBase : S, S2 {};
+struct VirtualBase : virtual Empty {};
+struct NonVirtualBase : Empty, S2 {};
-static_assert(!std::__libcpp_is_trivially_equality_comparable<S*, VirtualBase*>::value, "");
+static_assert(!std::__libcpp_is_trivially_equality_comparable<Empty*, VirtualBase*>::value, "");
static_assert(!std::__libcpp_is_trivially_equality_comparable<S2*, VirtualBase*>::value, "");
// This is trivially_equality_comparable, but we can't detect it currently
-static_assert(!std::__libcpp_is_trivially_equality_comparable<S*, NonVirtualBase*>::value, "");
+static_assert(!std::__libcpp_is_trivially_equality_comparable<Empty*, NonVirtualBase*>::value, "");
diff --git a/libcxx/test/libcxx/type_traits/is_trivially_relocatable.compile.pass.cpp b/libcxx/test/libcxx/type_traits/is_trivially_relocatable.compile.pass.cpp
new file mode 100644
index 00000000000000..3a1cf68135f8a7
--- /dev/null
+++ b/libcxx/test/libcxx/type_traits/is_trivially_relocatable.compile.pass.cpp
@@ -0,0 +1,100 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <__type_traits/is_trivially_relocatable.h>
+#include <memory>
+#include <string>
+
+#include "constexpr_char_traits.h"
+#include "test_allocator.h"
+
+static_assert(std::__libcpp_is_trivially_relocatable<char>::value);
+static_assert(std::__libcpp_is_trivially_relocatable<int>::value);
+static_assert(std::__libcpp_is_trivially_relocatable<double>::value);
+
+struct Empty {};
+static_assert(std::__libcpp_is_trivially_relocatable<Empty>::value);
+
+struct TriviallyCopyable {
+ char c;
+ int i;
+ Empty s;
+};
+static_assert(std::__libcpp_is_trivially_relocatable<TriviallyCopyable>::value);
+
+struct NotTriviallyCopyable {
+ NotTriviallyCopyable(const NotTriviallyCopyable&);
+ ~NotTriviallyCopyable();
+};
+static_assert(!std::__libcpp_is_trivially_relocatable<NotTriviallyCopyable>::value);
+
+struct MoveOnlyTriviallyCopyable {
+ MoveOnlyTriviallyCopyable(const MoveOnlyTriviallyCopyable&) = delete;
+ MoveOnlyTriviallyCopyable& operator=(const MoveOnlyTriviallyCopyable&) = delete;
+ MoveOnlyTriviallyCopyable(MoveOnlyTriviallyCopyable&&) = default;
+ MoveOnlyTriviallyCopyable& operator=(MoveOnlyTriviallyCopyable&&) = default;
+};
+static_assert(std::__libcpp_is_trivially_relocatable<MoveOnlyTriviallyCopyable>::value);
+
+// standard library types
+// ----------------------
+
+// basic_string
+struct MyChar {
+ char c;
+};
+template <class T>
+struct NotTriviallyRelocatableCharTraits : constexpr_char_traits<T> {
+ NotTriviallyRelocatableCharTraits(const NotTriviallyRelocatableCharTraits&);
+ NotTriviallyRelocatableCharTraits& operator=(const NotTriviallyRelocatableCharTraits&);
+ ~NotTriviallyRelocatableCharTraits();
+};
+
+static_assert(std::__libcpp_is_trivially_relocatable<
+ std::basic_string<char, std::char_traits<char>, std::allocator<char>>>::value);
+static_assert(std::__libcpp_is_trivially_relocatable<
+ std::basic_string<char, NotTriviallyRelocatableCharTraits<char>, std::allocator<char>>>::value);
+static_assert(std::__libcpp_is_trivially_relocatable<
+ std::basic_string<MyChar, constexpr_char_traits<MyChar>, std::allocator<MyChar>>>::value);
+static_assert(std::__libcpp_is_trivially_relocatable<
+ std::basic_string<MyChar, NotTriviallyRelocatableCharTraits<MyChar>, std::allocator<MyChar>>>::value);
+static_assert(!std::__libcpp_is_trivially_relocatable<
+ std::basic_string<char, std::char_traits<char>, test_allocator<char>>>::value);
+static_assert(!std::__libcpp_is_trivially_relocatable<
+ std::basic_string<MyChar, NotTriviallyRelocatableCharTraits<MyChar>, test_allocator<MyChar>>>::value);
+
+// unique_ptr
+struct NotTriviallyRelocatableDeleter {
+ NotTriviallyRelocatableDeleter(const NotTriviallyRelocatableDeleter&);
+ NotTriviallyRelocatableDeleter& operator=(const NotTriviallyRelocatableDeleter&);
+ ~NotTriviallyRelocatableDeleter();
+
+ template <class T>
+ void operator()(T*);
+};
+
+struct NotTriviallyRelocatablePointer {
+ struct pointer {
+ pointer(const pointer&);
+ pointer& operator=(const pointer&);
+ ~pointer();
+ };
+
+ template <class T>
+ void operator()(T*);
+};
+
+static_assert(std::__libcpp_is_trivially_relocatable<std::unique_ptr<int>>::value);
+static_assert(std::__libcpp_is_trivially_relocatable<std::unique_ptr<NotTriviallyCopyable>>::value);
+static_assert(std::__libcpp_is_trivially_relocatable<std::unique_ptr<int[]>>::value);
+static_assert(!std::__libcpp_is_trivially_relocatable<std::unique_ptr<int, NotTriviallyRelocatableDeleter>>::value);
+static_assert(!std::__libcpp_is_trivially_relocatable<std::unique_ptr<int[], NotTriviallyRelocatableDeleter>>::value);
+static_assert(!std::__libcpp_is_trivially_relocatable<std::unique_ptr<int, NotTriviallyRelocatablePointer>>::value);
+static_assert(!std::__libcpp_is_trivially_relocatable<std::unique_ptr<int[], NotTriviallyRelocatablePointer>>::value);
+
+// TODO: Mark all the trivially relocatable STL types as such
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