9827440f1e
Previously, the segmented iterator optimization was limited to `std::{for_each, for_each_n}`. This patch
extends the optimization to `std::ranges::for_each` and `std::ranges::for_each_n`, ensuring consistent
optimizations across these algorithms. This patch first generalizes the `std` algorithms by introducing
a `Projection` parameter, which is set to `__identity` for the `std` algorithms. Then we let the `ranges`
algorithms to directly call their `std` counterparts with a general `__proj` argument. Benchmarks
demonstrate performance improvements of up to 21.4x for ``std::deque::iterator`` and 22.3x for
``join_view`` of ``vector<vector<char>>``.
Addresses a subtask of #102817.
90 lines
3.1 KiB
C++
90 lines
3.1 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ALGORITHM_RANGES_FOR_EACH_H
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#define _LIBCPP___ALGORITHM_RANGES_FOR_EACH_H
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#include <__algorithm/for_each.h>
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#include <__algorithm/for_each_n.h>
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#include <__algorithm/in_fun_result.h>
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#include <__concepts/assignable.h>
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#include <__config>
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#include <__functional/identity.h>
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#include <__iterator/concepts.h>
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#include <__iterator/projected.h>
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#include <__ranges/access.h>
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#include <__ranges/concepts.h>
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#include <__ranges/dangling.h>
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#include <__utility/move.h>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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#if _LIBCPP_STD_VER >= 20
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_LIBCPP_BEGIN_NAMESPACE_STD
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namespace ranges {
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template <class _Iter, class _Func>
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using for_each_result = in_fun_result<_Iter, _Func>;
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struct __for_each {
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private:
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template <class _Iter, class _Sent, class _Proj, class _Func>
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_LIBCPP_HIDE_FROM_ABI constexpr static for_each_result<_Iter, _Func>
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__for_each_impl(_Iter __first, _Sent __last, _Func& __func, _Proj& __proj) {
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// In the case where we have different iterator and sentinel types, the segmented iterator optimization
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// in std::for_each will not kick in. Therefore, we prefer std::for_each_n in that case (whenever we can
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// obtain the `n`).
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if constexpr (!std::assignable_from<_Iter&, _Sent> && std::sized_sentinel_for<_Sent, _Iter>) {
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auto __n = __last - __first;
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auto __end = std::__for_each_n(std::move(__first), __n, __func, __proj);
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return {std::move(__end), std::move(__func)};
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} else {
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auto __end = std::__for_each(std::move(__first), std::move(__last), __func, __proj);
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return {std::move(__end), std::move(__func)};
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}
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}
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public:
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template <input_iterator _Iter,
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sentinel_for<_Iter> _Sent,
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class _Proj = identity,
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indirectly_unary_invocable<projected<_Iter, _Proj>> _Func>
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_LIBCPP_HIDE_FROM_ABI constexpr for_each_result<_Iter, _Func>
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operator()(_Iter __first, _Sent __last, _Func __func, _Proj __proj = {}) const {
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return __for_each_impl(std::move(__first), std::move(__last), __func, __proj);
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}
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template <input_range _Range,
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class _Proj = identity,
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indirectly_unary_invocable<projected<iterator_t<_Range>, _Proj>> _Func>
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_LIBCPP_HIDE_FROM_ABI constexpr for_each_result<borrowed_iterator_t<_Range>, _Func>
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operator()(_Range&& __range, _Func __func, _Proj __proj = {}) const {
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return __for_each_impl(ranges::begin(__range), ranges::end(__range), __func, __proj);
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}
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};
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inline namespace __cpo {
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inline constexpr auto for_each = __for_each{};
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} // namespace __cpo
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} // namespace ranges
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_STD_VER >= 20
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___ALGORITHM_RANGES_FOR_EACH_H
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