0621fd0b88
Part of #102817. This patch optimizes `rng::generate_n` for segmented iterators by forwarding the implementation directly to `std::generate_n`. - before ``` rng::generate_n(deque<int>)/32 21.7 ns 22.0 ns 32000000 rng::generate_n(deque<int>)/50 30.8 ns 30.7 ns 22400000 rng::generate_n(deque<int>)/1024 492 ns 488 ns 1120000 rng::generate_n(deque<int>)/8192 3938 ns 3924 ns 179200 ``` - after ``` rng::generate_n(deque<int>)/32 11.0 ns 11.0 ns 64000000 rng::generate_n(deque<int>)/50 16.2 ns 16.1 ns 40727273 rng::generate_n(deque<int>)/1024 292 ns 286 ns 2240000 rng::generate_n(deque<int>)/8192 2291 ns 2302 ns 298667 ```
58 lines
1.7 KiB
C++
58 lines
1.7 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_GENERATE_N_H
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#define _LIBCPP___ALGORITHM_RANGES_GENERATE_N_H
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#include <__algorithm/generate_n.h>
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#include <__concepts/constructible.h>
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#include <__concepts/invocable.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/incrementable_traits.h>
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#include <__iterator/iterator_traits.h>
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#include <__ranges/access.h>
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#include <__ranges/concepts.h>
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#include <__type_traits/invoke.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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struct __generate_n {
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template <input_or_output_iterator _OutIter, copy_constructible _Func>
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requires invocable<_Func&> && indirectly_writable<_OutIter, invoke_result_t<_Func&>>
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_LIBCPP_HIDE_FROM_ABI constexpr _OutIter
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operator()(_OutIter __first, iter_difference_t<_OutIter> __n, _Func __gen) const {
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return std::__generate_n(std::move(__first), __n, __gen);
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}
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};
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inline namespace __cpo {
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inline constexpr auto generate_n = __generate_n{};
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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_GENERATE_N_H
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