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[libc++] Support constexpr for std::stable_sort in radix sort branch #125284

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Merged
merged 3 commits into from
Feb 6, 2025
Merged

[libc++] Support constexpr for std::stable_sort in radix sort branch #125284

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6dbc307
constexpr
izvolov Feb 4, 2025
08a6649
test
izvolov Feb 4, 2025
6bf69ed
include
izvolov Feb 4, 2025
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25 changes: 13 additions & 12 deletions libcxx/include/__algorithm/radix_sort.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@
#include <__bit/countl.h>
#include <__config>
#include <__functional/identity.h>
#include <__iterator/access.h>
#include <__iterator/distance.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/move_iterator.h>
Expand Down Expand Up @@ -67,7 +68,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER >= 14

template <class _InputIterator, class _OutputIterator>
_LIBCPP_HIDE_FROM_ABI pair<_OutputIterator, __iter_value_type<_InputIterator>>
_LIBCPP_HIDE_FROM_ABI constexpr pair<_OutputIterator, __iter_value_type<_InputIterator>>
__partial_sum_max(_InputIterator __first, _InputIterator __last, _OutputIterator __result) {
if (__first == __last)
return {__result, 0};
Expand Down Expand Up @@ -109,15 +110,15 @@ struct __counting_sort_traits {
};

template <class _Radix, class _Integer>
_LIBCPP_HIDE_FROM_ABI auto __nth_radix(size_t __radix_number, _Radix __radix, _Integer __n) {
_LIBCPP_HIDE_FROM_ABI constexpr auto __nth_radix(size_t __radix_number, _Radix __radix, _Integer __n) {
static_assert(is_unsigned<_Integer>::value);
using __traits = __counting_sort_traits<_Integer, _Radix>;

return __radix(static_cast<_Integer>(__n >> __traits::__radix_size * __radix_number));
}

template <class _ForwardIterator, class _Map, class _RandomAccessIterator>
_LIBCPP_HIDE_FROM_ABI void
_LIBCPP_HIDE_FROM_ABI constexpr void
__collect(_ForwardIterator __first, _ForwardIterator __last, _Map __map, _RandomAccessIterator __counters) {
using __value_type = __iter_value_type<_ForwardIterator>;
using __traits = __counting_sort_traits<__value_type, _Map>;
Expand All @@ -129,7 +130,7 @@ __collect(_ForwardIterator __first, _ForwardIterator __last, _Map __map, _Random
}

template <class _ForwardIterator, class _RandomAccessIterator1, class _Map, class _RandomAccessIterator2>
_LIBCPP_HIDE_FROM_ABI void
_LIBCPP_HIDE_FROM_ABI constexpr void
__dispose(_ForwardIterator __first,
_ForwardIterator __last,
_RandomAccessIterator1 __result,
Expand All @@ -147,7 +148,7 @@ template <class _ForwardIterator,
class _RandomAccessIterator1,
class _RandomAccessIterator2,
size_t... _Radices>
_LIBCPP_HIDE_FROM_ABI bool __collect_impl(
_LIBCPP_HIDE_FROM_ABI constexpr bool __collect_impl(
_ForwardIterator __first,
_ForwardIterator __last,
_Map __map,
Expand Down Expand Up @@ -177,7 +178,7 @@ _LIBCPP_HIDE_FROM_ABI bool __collect_impl(
}

template <class _ForwardIterator, class _Map, class _Radix, class _RandomAccessIterator1, class _RandomAccessIterator2>
_LIBCPP_HIDE_FROM_ABI bool
_LIBCPP_HIDE_FROM_ABI constexpr bool
__collect(_ForwardIterator __first,
_ForwardIterator __last,
_Map __map,
Expand All @@ -191,7 +192,7 @@ __collect(_ForwardIterator __first,
}

template <class _BidirectionalIterator, class _RandomAccessIterator1, class _Map, class _RandomAccessIterator2>
_LIBCPP_HIDE_FROM_ABI void __dispose_backward(
_LIBCPP_HIDE_FROM_ABI constexpr void __dispose_backward(
_BidirectionalIterator __first,
_BidirectionalIterator __last,
_RandomAccessIterator1 __result,
Expand All @@ -206,7 +207,7 @@ _LIBCPP_HIDE_FROM_ABI void __dispose_backward(
}

template <class _ForwardIterator, class _RandomAccessIterator, class _Map>
_LIBCPP_HIDE_FROM_ABI _RandomAccessIterator
_LIBCPP_HIDE_FROM_ABI constexpr _RandomAccessIterator
__counting_sort_impl(_ForwardIterator __first, _ForwardIterator __last, _RandomAccessIterator __result, _Map __map) {
using __value_type = __iter_value_type<_ForwardIterator>;
using __traits = __counting_sort_traits<__value_type, _Map>;
Expand All @@ -225,7 +226,7 @@ template <class _RandomAccessIterator1,
class _Radix,
enable_if_t< __radix_sort_traits<__iter_value_type<_RandomAccessIterator1>, _Map, _Radix>::__radix_count == 1,
int> = 0>
_LIBCPP_HIDE_FROM_ABI void __radix_sort_impl(
_LIBCPP_HIDE_FROM_ABI constexpr void __radix_sort_impl(
_RandomAccessIterator1 __first,
_RandomAccessIterator1 __last,
_RandomAccessIterator2 __buffer,
Expand All @@ -245,7 +246,7 @@ template <
class _Radix,
enable_if_t< __radix_sort_traits<__iter_value_type<_RandomAccessIterator1>, _Map, _Radix>::__radix_count % 2 == 0,
int> = 0 >
_LIBCPP_HIDE_FROM_ABI void __radix_sort_impl(
_LIBCPP_HIDE_FROM_ABI constexpr void __radix_sort_impl(
_RandomAccessIterator1 __first,
_RandomAccessIterator1 __last,
_RandomAccessIterator2 __buffer_begin,
Expand Down Expand Up @@ -307,7 +308,7 @@ struct __low_byte_fn {
};

template <class _RandomAccessIterator1, class _RandomAccessIterator2, class _Map, class _Radix>
_LIBCPP_HIDE_FROM_ABI void
_LIBCPP_HIDE_FROM_ABI constexpr void
__radix_sort(_RandomAccessIterator1 __first,
_RandomAccessIterator1 __last,
_RandomAccessIterator2 __buffer,
Expand All @@ -318,7 +319,7 @@ __radix_sort(_RandomAccessIterator1 __first,
}

template <class _RandomAccessIterator1, class _RandomAccessIterator2>
_LIBCPP_HIDE_FROM_ABI void
_LIBCPP_HIDE_FROM_ABI constexpr void
__radix_sort(_RandomAccessIterator1 __first, _RandomAccessIterator1 __last, _RandomAccessIterator2 __buffer) {
std::__radix_sort(__first, __last, __buffer, __identity{}, __low_byte_fn{});
}
Expand Down
7 changes: 7 additions & 0 deletions libcxx/include/__algorithm/stable_sort.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
#include <__memory/unique_temporary_buffer.h>
#include <__type_traits/desugars_to.h>
#include <__type_traits/enable_if.h>
#include <__type_traits/is_constant_evaluated.h>
#include <__type_traits/is_integral.h>
#include <__type_traits/is_same.h>
#include <__type_traits/is_trivially_assignable.h>
Expand Down Expand Up @@ -253,6 +254,12 @@ _LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
if constexpr (__allowed_radix_sort) {
if (__len <= __buff_size && __len >= static_cast<difference_type>(__radix_sort_min_bound<value_type>()) &&
__len <= static_cast<difference_type>(__radix_sort_max_bound<value_type>())) {
if (__libcpp_is_constant_evaluated()) {
for (auto* __p = __buff; __p < __buff + __buff_size; ++__p) {
std::__construct_at(__p);
}
}

std::__radix_sort(__first, __last, __buff);
return;
}
Expand Down
2 changes: 2 additions & 0 deletions libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
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Expand Up @@ -199,6 +199,8 @@ int main(int, char**) {
#if TEST_STD_VER >= 26
static_assert(test<int>());
static_assert(test<float>());
// test constexprness of radix sort branch
static_assert(test<char>());
#endif
return 0;
}