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005916de58
Instead of using `reverse_iterator`, share the optimization between the 4 algorithms. The key observation here that `memmove` applies to both `copy` and `move` identically, and to their `_backward` versions very similarly. All algorithms now follow the same pattern along the lines of:
```
if constexpr (can_memmove<InIter, OutIter>) {
memmove(first, last, out);
} else {
naive_implementation(first, last, out);
}
```
A follow-up will delete `unconstrained_reverse_iterator`.
This patch removes duplication and divergence between `std::copy`, `std::move` and `std::move_backward`. It also improves testing:
- the test for whether the optimization is used only applied to `std::copy` and, more importantly, was essentially a no-op because it would still pass if the optimization was not used;
- there were no tests to make sure the optimization is not used when the effect would be visible.
Differential Revision: https://reviews.llvm.org/D130695
102 lines
3.7 KiB
C++
102 lines
3.7 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_SET_UNION_H
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#define _LIBCPP___ALGORITHM_SET_UNION_H
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#include <__algorithm/comp.h>
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#include <__algorithm/comp_ref_type.h>
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#include <__algorithm/copy.h>
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#include <__algorithm/iterator_operations.h>
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#include <__config>
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#include <__iterator/iterator_traits.h>
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#include <__utility/move.h>
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#include <__utility/pair.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_BEGIN_NAMESPACE_STD
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template <class _InIter1, class _InIter2, class _OutIter>
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struct __set_union_result {
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_InIter1 __in1_;
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_InIter2 __in2_;
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_OutIter __out_;
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// need a constructor as C++03 aggregate init is hard
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
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__set_union_result(_InIter1&& __in_iter1, _InIter2&& __in_iter2, _OutIter&& __out_iter)
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: __in1_(std::move(__in_iter1)), __in2_(std::move(__in_iter2)), __out_(std::move(__out_iter)) {}
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};
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template <class _AlgPolicy, class _Compare, class _InIter1, class _Sent1, class _InIter2, class _Sent2, class _OutIter>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __set_union_result<_InIter1, _InIter2, _OutIter> __set_union(
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_InIter1 __first1, _Sent1 __last1, _InIter2 __first2, _Sent2 __last2, _OutIter __result, _Compare&& __comp) {
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for (; __first1 != __last1; ++__result) {
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if (__first2 == __last2) {
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auto __ret1 = std::__copy<_AlgPolicy>(std::move(__first1), std::move(__last1), std::move(__result));
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return __set_union_result<_InIter1, _InIter2, _OutIter>(
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std::move(__ret1.first), std::move(__first2), std::move((__ret1.second)));
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}
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if (__comp(*__first2, *__first1)) {
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*__result = *__first2;
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++__first2;
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} else {
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if (!__comp(*__first1, *__first2)) {
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++__first2;
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}
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*__result = *__first1;
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++__first1;
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}
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}
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auto __ret2 = std::__copy<_AlgPolicy>(std::move(__first2), std::move(__last2), std::move(__result));
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return __set_union_result<_InIter1, _InIter2, _OutIter>(
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std::move(__first1), std::move(__ret2.first), std::move((__ret2.second)));
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}
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template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator set_union(
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_InputIterator1 __first1,
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_InputIterator1 __last1,
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_InputIterator2 __first2,
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_InputIterator2 __last2,
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_OutputIterator __result,
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_Compare __comp) {
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return std::__set_union<_ClassicAlgPolicy, __comp_ref_type<_Compare> >(
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std::move(__first1),
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std::move(__last1),
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std::move(__first2),
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std::move(__last2),
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std::move(__result),
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__comp)
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.__out_;
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}
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template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator set_union(
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_InputIterator1 __first1,
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_InputIterator1 __last1,
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_InputIterator2 __first2,
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_InputIterator2 __last2,
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_OutputIterator __result) {
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return std::set_union(
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std::move(__first1),
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std::move(__last1),
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std::move(__first2),
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std::move(__last2),
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std::move(__result),
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__less<typename iterator_traits<_InputIterator1>::value_type,
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typename iterator_traits<_InputIterator2>::value_type>());
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}
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___ALGORITHM_SET_UNION_H
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