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[libc++] Forward calls to ranges::swap_ranges to the 3-leg implementation if possible (#176762)

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This allows us to make use of any optimizations to `std::swap_ranges` in
`ranges::swap_ranges`.

This patch also moves some code specific to `ranges::swap_ranges` into
`ranges_swap_ranges.h`.
This commit is contained in:
Nikolas Klauser 2026-01-27 16:25:41 +01:00 committed by GitHub
parent 28d621e752
commit c48be319db
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GPG key ID: B5690EEEBB952194
2 changed files with 30 additions and 30 deletions
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33
libcxx/include/__algorithm/ranges_swap_ranges.h
View file

@ -11,6 +11,7 @@
#include <__algorithm/in_in_result.h>
#include <__algorithm/iterator_operations.h>
#include <__algorithm/min.h>
#include <__algorithm/swap_ranges.h>
#include <__config>
#include <__iterator/concepts.h>
@ -18,7 +19,9 @@
#include <__ranges/access.h>
#include <__ranges/concepts.h>
#include <__ranges/dangling.h>
#include <__type_traits/is_same.h>
#include <__utility/move.h>
#include <__utility/pair.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
@ -41,9 +44,33 @@ struct __swap_ranges {
requires indirectly_swappable<_I1, _I2>
_LIBCPP_HIDE_FROM_ABI constexpr swap_ranges_result<_I1, _I2>
operator()(_I1 __first1, _S1 __last1, _I2 __first2, _S2 __last2) const {
auto __ret = std::__swap_ranges<_RangeAlgPolicy>(
std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2));
return {std::move(__ret.first), std::move(__ret.second)};
if constexpr (sized_sentinel_for<_I1, _S1> && sized_sentinel_for<_I2, _S2> &&
(random_access_iterator<_I1> || random_access_iterator<_I2> ||
(is_same_v<_I1, _S1> && is_same_v<_I2, _S2>))) {
auto __offset = std::min(__last1 - __first1, __last2 - __first2);
auto __ret = [&] {
if constexpr (random_access_iterator<_I1>)
return std::__swap_ranges<_RangeAlgPolicy>(__first1, __first1 + __offset, std::move(__first2));
else if constexpr (random_access_iterator<_I2>)
return std::__swap_ranges<_RangeAlgPolicy>(__first2, __first2 + __offset, std::move(__first1));
else if (__last2 - __first2 < __last1 - __first1) {
auto __reversed =
std::__swap_ranges<_RangeAlgPolicy>(std::move(__first2), std::move(__last2), std::move(__first1));
return std::pair<_I1, _I2>(std::move(__reversed.second), std::move(__reversed.first));
} else
return std::__swap_ranges<_RangeAlgPolicy>(std::move(__first1), std::move(__last1), std::move(__first2));
}();
return {std::move(__ret.first), std::move(__ret.second)};
} else {
while (__first1 != __last1 && __first2 != __last2) {
ranges::iter_swap(__first1, __first2);
++__first1;
++__first2;
}
return {std::move(__first1), std::move(__first2)};
}
}
template <input_range _R1, input_range _R2>

27
libcxx/include/__algorithm/swap_ranges.h
View file

@ -162,7 +162,6 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __bit_iterator<_Cr, false> _
return __result;
}
// 2+1 iterators: size2 >= size1; used by std::swap_ranges.
template <class, class _Cl, class _Cr>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<__bit_iterator<_Cl, false>, __bit_iterator<_Cr, false> >
__swap_ranges(__bit_iterator<_Cl, false> __first1,
@ -173,32 +172,6 @@ __swap_ranges(__bit_iterator<_Cl, false> __first1,
return std::make_pair(__last1, std::__swap_ranges_unaligned(__first1, __last1, __first2));
}
// 2+2 iterators: used by std::ranges::swap_ranges.
template <class _AlgPolicy, class _Cl, class _Cr>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<__bit_iterator<_Cl, false>, __bit_iterator<_Cr, false> >
__swap_ranges(__bit_iterator<_Cl, false> __first1,
__bit_iterator<_Cl, false> __last1,
__bit_iterator<_Cr, false> __first2,
__bit_iterator<_Cr, false> __last2) {
if (__last1 - __first1 < __last2 - __first2)
return std::make_pair(__last1, std::__swap_ranges<_AlgPolicy>(__first1, __last1, __first2).second);
return std::make_pair(std::__swap_ranges<_AlgPolicy>(__first2, __last2, __first1).second, __last2);
}
// 2+2 iterators: the shorter size will be used.
template <class _AlgPolicy, class _ForwardIterator1, class _Sentinel1, class _ForwardIterator2, class _Sentinel2>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator1, _ForwardIterator2>
__swap_ranges(_ForwardIterator1 __first1, _Sentinel1 __last1, _ForwardIterator2 __first2, _Sentinel2 __last2) {
while (__first1 != __last1 && __first2 != __last2) {
_IterOps<_AlgPolicy>::iter_swap(__first1, __first2);
++__first1;
++__first2;
}
return pair<_ForwardIterator1, _ForwardIterator2>(std::move(__first1), std::move(__first2));
}
// 2+1 iterators: size2 >= size1.
template <class _AlgPolicy, class _ForwardIterator1, class _Sentinel1, class _ForwardIterator2>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator1, _ForwardIterator2>
__swap_ranges(_ForwardIterator1 __first1, _Sentinel1 __last1, _ForwardIterator2 __first2) {