[libcxx-commits] [libcxx] [libc++] Support `constexpr` for `std::stable_sort` in radix sort branch (PR #125284)
Дмитрий Изволов via libcxx-commits
libcxx-commits at lists.llvm.org
Mon Feb 3 23:20:03 PST 2025
https://github.com/izvolov updated https://github.com/llvm/llvm-project/pull/125284
>From 6dbc30721a7378878da01faaf0bad6795a4a0302 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Tue, 4 Feb 2025 10:19:19 +0300
Subject: [PATCH 1/2] constexpr
---
libcxx/include/__algorithm/radix_sort.h | 24 ++++++++++++------------
libcxx/include/__algorithm/stable_sort.h | 7 +++++++
2 files changed, 19 insertions(+), 12 deletions(-)
diff --git a/libcxx/include/__algorithm/radix_sort.h b/libcxx/include/__algorithm/radix_sort.h
index de6927995e74c8..89df4e19fd00fb 100644
--- a/libcxx/include/__algorithm/radix_sort.h
+++ b/libcxx/include/__algorithm/radix_sort.h
@@ -67,7 +67,7 @@ _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};
@@ -109,7 +109,7 @@ 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>;
@@ -117,7 +117,7 @@ _LIBCPP_HIDE_FROM_ABI auto __nth_radix(size_t __radix_number, _Radix __radix, _I
}
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>;
@@ -129,7 +129,7 @@ __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,
@@ -147,7 +147,7 @@ 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,
@@ -177,7 +177,7 @@ _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,
@@ -191,7 +191,7 @@ __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,
@@ -206,7 +206,7 @@ _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>;
@@ -225,7 +225,7 @@ 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,
@@ -245,7 +245,7 @@ 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,
@@ -307,7 +307,7 @@ 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,
@@ -318,7 +318,7 @@ __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{});
}
diff --git a/libcxx/include/__algorithm/stable_sort.h b/libcxx/include/__algorithm/stable_sort.h
index 3cfbcf08d2c5c4..49d3cca2526ead 100644
--- a/libcxx/include/__algorithm/stable_sort.h
+++ b/libcxx/include/__algorithm/stable_sort.h
@@ -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>
@@ -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;
}
>From 08a6649df23c14f300ae6fc31c30b36e4ae2525e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20=D0=98=D0=B7?=
=?UTF-8?q?=D0=B2=D0=BE=D0=BB=D0=BE=D0=B2?= <dmitriy at izvolov.ru>
Date: Tue, 4 Feb 2025 10:19:26 +0300
Subject: [PATCH 2/2] test
---
.../alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp | 2 ++
1 file changed, 2 insertions(+)
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
index b3b458808c44ad..4ee1d795a23b26 100644
--- a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp
@@ -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;
}
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