[libcxx-commits] [libcxx] [libc++] Support `constexpr` for `std::stable_sort` in radix sort branch (PR #125284)
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Fri Jan 31 12:17:27 PST 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: Дмитрий Изволов (izvolov)
<details>
<summary>Changes</summary>
`std::stable_sort` is `constexpr` since PR https://github.com/llvm/llvm-project/pull/110320
But `radix_sort` branch is still non-`constexpr`.
This PR fixes it.
#<!-- -->119394
#<!-- -->105360
---
Full diff: https://github.com/llvm/llvm-project/pull/125284.diff
3 Files Affected:
- (modified) libcxx/include/__algorithm/radix_sort.h (+12-12)
- (modified) libcxx/include/__algorithm/stable_sort.h (+6)
- (modified) libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp (+2-1)
``````````diff
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..21bc3a947069c0 100644
--- a/libcxx/include/__algorithm/stable_sort.h
+++ b/libcxx/include/__algorithm/stable_sort.h
@@ -253,6 +253,12 @@ _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>())) {
+ for (auto* p = __buff; p < __buff + __buff_size; ++p) {
+ std::__construct_at(p, 0);
+ }
+ __destruct_n __d(__buff_size);
+ unique_ptr<value_type, __destruct_n&> __h2(__buff, __d);
+
std::__radix_sort(__first, __last, __buff);
return;
}
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..1e529529b78f96 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
@@ -178,8 +178,9 @@ TEST_CONSTEXPR_CXX26 bool test() {
test_larger_sorts<T>(1009);
test_larger_sorts<T>(1024);
test_larger_sorts<T>(1031);
- test_larger_sorts<T>(2053);
}
+ // test constexprness of radix sort branch
+ test_larger_sorts<T>(2053);
// check that the algorithm works without memory
#ifndef TEST_HAS_NO_EXCEPTIONS
``````````
</details>
https://github.com/llvm/llvm-project/pull/125284
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