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[libc++][C++26] P2562R1: constexpr Stable Sorting #110320

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[libc++][C++26] P2562R1: constexpr Stable Sorting #110320

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477f2f3
constexpr stable_sort
PaulXiCao Sep 27, 2024
5dbcf56
tests
PaulXiCao Sep 27, 2024
0733a85
update algorithm synopsis
PaulXiCao Sep 27, 2024
db314e2
update docs
PaulXiCao Sep 27, 2024
8221f44
paper status: partial
PaulXiCao Oct 2, 2024
7abb0b8
remove include of internal header
PaulXiCao Oct 4, 2024
da3173c
replace _LIBCPP_CONSTEXPR_SINCE_CXX26 by TEST_CONSTEXPR_CXX26
PaulXiCao Oct 4, 2024
5f518d2
documentation: use proper function declaration
PaulXiCao Oct 4, 2024
693c338
workaround for gcc bug with placement new
PaulXiCao Oct 5, 2024
e401b3c
workaround for gcc bug with placement new: fix lambda capturing
PaulXiCao Oct 6, 2024
514ecdb
workaround for gcc bug with placement new: v3
PaulXiCao Oct 6, 2024
39f2aff
workaround for gcc bug with placement new: v4
PaulXiCao Oct 6, 2024
1fe36c2
workaround for gcc bug with placement new: v5 (test)
PaulXiCao Oct 11, 2024
f6cc51b
workaround for gcc bug with placement new: v6
PaulXiCao Oct 12, 2024
d7c4fa9
workaround for gcc bug with placement new: v7
PaulXiCao Oct 13, 2024
c3470a2
test: use TEST_STD_VER
PaulXiCao Oct 13, 2024
6bd6297
increase constexpr-steps as unstable abi tests cause more evaluation …
PaulXiCao Oct 18, 2024
e93a630
simplify testing (possible b.c. increase of constexpr-steps)
PaulXiCao Oct 18, 2024
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2 changes: 1 addition & 1 deletion libcxx/docs/Status/Cxx2cPapers.csv
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
"`P2497R0 <https://wg21.link/P2497R0>`__","Testing for success or failure of ``<charconv>`` functions","2023-06 (Varna)","|Complete|","18.0",""
"`P2592R3 <https://wg21.link/P2592R3>`__","Hashing support for ``std::chrono`` value classes","2023-06 (Varna)","","",""
"`P2587R3 <https://wg21.link/P2587R3>`__","``to_string`` or not ``to_string``","2023-06 (Varna)","","",""
"`P2562R1 <https://wg21.link/P2562R1>`__","``constexpr`` Stable Sorting","2023-06 (Varna)","","",""
"`P2562R1 <https://wg21.link/P2562R1>`__","``constexpr`` Stable Sorting","2023-06 (Varna)","|Partial|","20.0",""
"`P2545R4 <https://wg21.link/P2545R4>`__","Read-Copy Update (RCU)","2023-06 (Varna)","","",""
"`P2530R3 <https://wg21.link/P2530R3>`__","Hazard Pointers for C++26","2023-06 (Varna)","","",""
"`P2538R1 <https://wg21.link/P2538R1>`__","ADL-proof ``std::projected``","2023-06 (Varna)","|Complete|","18.0",""
Expand Down
2 changes: 1 addition & 1 deletion libcxx/include/__algorithm/sort.h
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Expand Up @@ -283,7 +283,7 @@ __selection_sort(_BidirectionalIterator __first, _BidirectionalIterator __last,
// Sort the iterator range [__first, __last) using the comparator __comp using
// the insertion sort algorithm.
template <class _AlgPolicy, class _Compare, class _BidirectionalIterator>
_LIBCPP_HIDE_FROM_ABI void
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void
__insertion_sort(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp) {
using _Ops = _IterOps<_AlgPolicy>;

Expand Down
101 changes: 67 additions & 34 deletions libcxx/include/__algorithm/stable_sort.h
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Expand Up @@ -34,6 +34,26 @@ _LIBCPP_PUSH_MACROS

_LIBCPP_BEGIN_NAMESPACE_STD

// Workaround for "constexpr placement new" bug in gcc (fixed in 14.2).
// See https://github.com/llvm/llvm-project/pull/110320#discussion_r1788557715.
#define __STABLE_SORT_NEW_IMPL(__placement_arg, __type, __new_initializer_func, __new_initializer_arg) \
do { \
::new ((void*)__placement_arg) __type(__new_initializer_func(__new_initializer_arg)); \
} while (0)
#if !defined(__clang__) && defined(__GNUC__) && (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 <= 140100)
# define __STABLE_SORT_NEW(__placement_arg, __type, __new_initializer_func, __new_initializer_arg) \
do { \
[__placement_arg, &__new_initializer_arg] { \
__STABLE_SORT_NEW_IMPL(__placement_arg, __type, __new_initializer_func, __new_initializer_arg); \
}(); \
} while (0)
#else
# define __STABLE_SORT_NEW(__placement_arg, __type, __new_initializer_func, __new_initializer_arg) \
do { \
__STABLE_SORT_NEW_IMPL(__placement_arg, __type, __new_initializer_func, __new_initializer_arg); \
} while (0)
#endif
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template <class _AlgPolicy, class _Compare, class _BidirectionalIterator>
_LIBCPP_HIDE_FROM_ABI void __insertion_sort_move(
_BidirectionalIterator __first1,
Expand All @@ -47,19 +67,22 @@ _LIBCPP_HIDE_FROM_ABI void __insertion_sort_move(
__destruct_n __d(0);
unique_ptr<value_type, __destruct_n&> __h(__first2, __d);
value_type* __last2 = __first2;
::new ((void*)__last2) value_type(_Ops::__iter_move(__first1));
__STABLE_SORT_NEW(__last2, value_type, _Ops::__iter_move, __first1);
__d.template __incr<value_type>();
for (++__last2; ++__first1 != __last1; ++__last2) {
value_type* __j2 = __last2;
value_type* __i2 = __j2;
if (__comp(*__first1, *--__i2)) {
::new ((void*)__j2) value_type(std::move(*__i2));
{
value_type& __tmp = *__i2;
__STABLE_SORT_NEW(__j2, value_type, std::move, __tmp);
}
__d.template __incr<value_type>();
for (--__j2; __i2 != __first2 && __comp(*__first1, *--__i2); --__j2)
*__j2 = std::move(*__i2);
*__j2 = _Ops::__iter_move(__first1);
} else {
::new ((void*)__j2) value_type(_Ops::__iter_move(__first1));
__STABLE_SORT_NEW(__j2, value_type, _Ops::__iter_move, __first1);
__d.template __incr<value_type>();
}
}
Expand All @@ -68,7 +91,7 @@ _LIBCPP_HIDE_FROM_ABI void __insertion_sort_move(
}

template <class _AlgPolicy, class _Compare, class _InputIterator1, class _InputIterator2>
_LIBCPP_HIDE_FROM_ABI void __merge_move_construct(
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __merge_move_construct(
_InputIterator1 __first1,
_InputIterator1 __last1,
_InputIterator2 __first2,
Expand All @@ -83,30 +106,35 @@ _LIBCPP_HIDE_FROM_ABI void __merge_move_construct(
for (; true; ++__result) {
if (__first1 == __last1) {
for (; __first2 != __last2; ++__first2, (void)++__result, __d.template __incr<value_type>())
::new ((void*)__result) value_type(_Ops::__iter_move(__first2));
__STABLE_SORT_NEW(__result, value_type, _Ops::__iter_move, __first2);
__h.release();
return;
}
if (__first2 == __last2) {
for (; __first1 != __last1; ++__first1, (void)++__result, __d.template __incr<value_type>())
::new ((void*)__result) value_type(_Ops::__iter_move(__first1));
__STABLE_SORT_NEW(__result, value_type, _Ops::__iter_move, __first1);
__h.release();
return;
}
if (__comp(*__first2, *__first1)) {
::new ((void*)__result) value_type(_Ops::__iter_move(__first2));
__STABLE_SORT_NEW(__result, value_type, _Ops::__iter_move, __first2);
__d.template __incr<value_type>();
++__first2;
} else {
// __STABLE_SORT_NEW(__result, value_type, _Ops::__iter_move, __first1);
#if !defined(__clang__) && defined(__GNUC__) && (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 <= 140100)
[__result, &__first1] { ::new ((void*)__result) value_type(_Ops::__iter_move(__first1)); }();
#else
::new ((void*)__result) value_type(_Ops::__iter_move(__first1));
#endif
__d.template __incr<value_type>();
++__first1;
}
}
}

template <class _AlgPolicy, class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
_LIBCPP_HIDE_FROM_ABI void __merge_move_assign(
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __merge_move_assign(
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_InputIterator1 __first1,
_InputIterator1 __last1,
_InputIterator2 __first2,
Expand Down Expand Up @@ -134,41 +162,43 @@ _LIBCPP_HIDE_FROM_ABI void __merge_move_assign(
}

template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
void __stable_sort(_RandomAccessIterator __first,
_RandomAccessIterator __last,
_Compare __comp,
typename iterator_traits<_RandomAccessIterator>::difference_type __len,
typename iterator_traits<_RandomAccessIterator>::value_type* __buff,
ptrdiff_t __buff_size);
_LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
_RandomAccessIterator __first,
_RandomAccessIterator __last,
_Compare __comp,
typename iterator_traits<_RandomAccessIterator>::difference_type __len,
typename iterator_traits<_RandomAccessIterator>::value_type* __buff,
ptrdiff_t __buff_size);

template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
void __stable_sort_move(_RandomAccessIterator __first1,
_RandomAccessIterator __last1,
_Compare __comp,
typename iterator_traits<_RandomAccessIterator>::difference_type __len,
typename iterator_traits<_RandomAccessIterator>::value_type* __first2) {
_LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort_move(
_RandomAccessIterator __first1,
_RandomAccessIterator __last1,
_Compare __comp,
typename iterator_traits<_RandomAccessIterator>::difference_type __len,
typename iterator_traits<_RandomAccessIterator>::value_type* __first2) {
using _Ops = _IterOps<_AlgPolicy>;

typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
switch (__len) {
case 0:
return;
case 1:
::new ((void*)__first2) value_type(_Ops::__iter_move(__first1));
__STABLE_SORT_NEW(__first2, value_type, _Ops::__iter_move, __first1);
return;
case 2:
__destruct_n __d(0);
unique_ptr<value_type, __destruct_n&> __h2(__first2, __d);
if (__comp(*--__last1, *__first1)) {
::new ((void*)__first2) value_type(_Ops::__iter_move(__last1));
__STABLE_SORT_NEW(__first2, value_type, _Ops::__iter_move, __last1);
__d.template __incr<value_type>();
++__first2;
::new ((void*)__first2) value_type(_Ops::__iter_move(__first1));
__STABLE_SORT_NEW(__first2, value_type, _Ops::__iter_move, __first1);
} else {
::new ((void*)__first2) value_type(_Ops::__iter_move(__first1));
__STABLE_SORT_NEW(__first2, value_type, _Ops::__iter_move, __first1);
__d.template __incr<value_type>();
++__first2;
::new ((void*)__first2) value_type(_Ops::__iter_move(__last1));
__STABLE_SORT_NEW(__first2, value_type, _Ops::__iter_move, __last1);
}
__h2.release();
return;
Expand All @@ -190,12 +220,13 @@ struct __stable_sort_switch {
};

template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
void __stable_sort(_RandomAccessIterator __first,
_RandomAccessIterator __last,
_Compare __comp,
typename iterator_traits<_RandomAccessIterator>::difference_type __len,
typename iterator_traits<_RandomAccessIterator>::value_type* __buff,
ptrdiff_t __buff_size) {
_LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
_RandomAccessIterator __first,
_RandomAccessIterator __last,
_Compare __comp,
typename iterator_traits<_RandomAccessIterator>::difference_type __len,
typename iterator_traits<_RandomAccessIterator>::value_type* __buff,
ptrdiff_t __buff_size) {
typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
switch (__len) {
Expand Down Expand Up @@ -235,7 +266,7 @@ void __stable_sort(_RandomAccessIterator __first,
}

template <class _AlgPolicy, class _RandomAccessIterator, class _Compare>
inline _LIBCPP_HIDE_FROM_ABI void
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void
__stable_sort_impl(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare& __comp) {
using value_type = typename iterator_traits<_RandomAccessIterator>::value_type;
using difference_type = typename iterator_traits<_RandomAccessIterator>::difference_type;
Expand All @@ -254,18 +285,20 @@ __stable_sort_impl(_RandomAccessIterator __first, _RandomAccessIterator __last,
}

template <class _RandomAccessIterator, class _Compare>
inline _LIBCPP_HIDE_FROM_ABI void
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void
stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp) {
std::__stable_sort_impl<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __comp);
}

template <class _RandomAccessIterator>
inline _LIBCPP_HIDE_FROM_ABI void stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last) {
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void
stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last) {
std::stable_sort(__first, __last, __less<>());
}

#undef __STABLE_SORT_NEW
#undef __STABLE_SORT_NEW_IMPL
_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___ALGORITHM_STABLE_SORT_H
20 changes: 10 additions & 10 deletions libcxx/include/__memory/destruct_n.h
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Expand Up @@ -25,35 +25,35 @@ struct __destruct_n {
size_t __size_;

template <class _Tp>
_LIBCPP_HIDE_FROM_ABI void __process(_Tp* __p, false_type) _NOEXCEPT {
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __process(_Tp* __p, false_type) _NOEXCEPT {
for (size_t __i = 0; __i < __size_; ++__i, ++__p)
__p->~_Tp();
}

template <class _Tp>
_LIBCPP_HIDE_FROM_ABI void __process(_Tp*, true_type) _NOEXCEPT {}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __process(_Tp*, true_type) _NOEXCEPT {}

_LIBCPP_HIDE_FROM_ABI void __incr(false_type) _NOEXCEPT { ++__size_; }
_LIBCPP_HIDE_FROM_ABI void __incr(true_type) _NOEXCEPT {}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __incr(false_type) _NOEXCEPT { ++__size_; }
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __incr(true_type) _NOEXCEPT {}

_LIBCPP_HIDE_FROM_ABI void __set(size_t __s, false_type) _NOEXCEPT { __size_ = __s; }
_LIBCPP_HIDE_FROM_ABI void __set(size_t, true_type) _NOEXCEPT {}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __set(size_t __s, false_type) _NOEXCEPT { __size_ = __s; }
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __set(size_t, true_type) _NOEXCEPT {}

public:
_LIBCPP_HIDE_FROM_ABI explicit __destruct_n(size_t __s) _NOEXCEPT : __size_(__s) {}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 explicit __destruct_n(size_t __s) _NOEXCEPT : __size_(__s) {}

template <class _Tp>
_LIBCPP_HIDE_FROM_ABI void __incr() _NOEXCEPT {
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __incr() _NOEXCEPT {
__incr(integral_constant<bool, is_trivially_destructible<_Tp>::value>());
}

template <class _Tp>
_LIBCPP_HIDE_FROM_ABI void __set(size_t __s, _Tp*) _NOEXCEPT {
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void __set(size_t __s, _Tp*) _NOEXCEPT {
__set(__s, integral_constant<bool, is_trivially_destructible<_Tp>::value>());
}

template <class _Tp>
_LIBCPP_HIDE_FROM_ABI void operator()(_Tp* __p) _NOEXCEPT {
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void operator()(_Tp* __p) _NOEXCEPT {
__process(__p, integral_constant<bool, is_trivially_destructible<_Tp>::value>());
}
};
Expand Down
4 changes: 2 additions & 2 deletions libcxx/include/algorithm
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Original file line number Diff line number Diff line change
Expand Up @@ -1530,11 +1530,11 @@ template <class RandomAccessIterator, class Compare>
sort(RandomAccessIterator first, RandomAccessIterator last, Compare comp);

template <class RandomAccessIterator>
void
constexpr void // constexpr in C++26
stable_sort(RandomAccessIterator first, RandomAccessIterator last);

template <class RandomAccessIterator, class Compare>
void
constexpr void // constexpr in C++26
stable_sort(RandomAccessIterator first, RandomAccessIterator last, Compare comp);

template <class RandomAccessIterator>
Expand Down
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