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[libc++] Optimize most of the __tree search algorithms #155245
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,50 @@ | ||
| //===----------------------------------------------------------------------===// | ||
| // | ||
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | ||
| // See https://llvm.org/LICENSE.txt for license information. | ||
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||
| // | ||
| //===----------------------------------------------------------------------===// | ||
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| #ifndef _LIBCPP___UTILITY_DEFAULT_THREE_WAY_COMPARATOR_H | ||
| #define _LIBCPP___UTILITY_DEFAULT_THREE_WAY_COMPARATOR_H | ||
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| #include <__config> | ||
| #include <__type_traits/enable_if.h> | ||
| #include <__type_traits/is_arithmetic.h> | ||
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| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) | ||
| # pragma GCC system_header | ||
| #endif | ||
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| _LIBCPP_BEGIN_NAMESPACE_STD | ||
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| // This struct can be specialized to provide a three way comparator between _LHS and _RHS. | ||
| // The return value should be | ||
| // - less than zero if (lhs_val < rhs_val) | ||
| // - greater than zero if (rhs_val < lhs_val) | ||
| // - zero otherwise | ||
| template <class _LHS, class _RHS, class = void> | ||
| struct __default_three_way_comparator; | ||
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| template <class _Tp> | ||
| struct __default_three_way_comparator<_Tp, _Tp, __enable_if_t<is_arithmetic<_Tp>::value> > { | ||
| _LIBCPP_HIDE_FROM_ABI static int operator()(_Tp __lhs, _Tp __rhs) { | ||
| if (__lhs < __rhs) | ||
| return -1; | ||
| if (__lhs > __rhs) | ||
| return 1; | ||
| return 0; | ||
| } | ||
| }; | ||
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| template <class _LHS, class _RHS, bool = true> | ||
| inline const bool __has_default_three_way_comparator_v = false; | ||
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| template <class _LHS, class _RHS> | ||
| inline const bool | ||
| __has_default_three_way_comparator_v< _LHS, _RHS, sizeof(__default_three_way_comparator<_LHS, _RHS>) >= 0> = true; | ||
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| _LIBCPP_END_NAMESPACE_STD | ||
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| #endif // _LIBCPP___UTILITY_DEFAULT_THREE_WAY_COMPARATOR_H |
90 changes: 90 additions & 0 deletions
90
libcxx/include/__utility/lazy_synth_three_way_comparator.h
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,90 @@ | ||
| //===----------------------------------------------------------------------===// | ||
| // | ||
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | ||
| // See https://llvm.org/LICENSE.txt for license information. | ||
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||
| // | ||
| //===----------------------------------------------------------------------===// | ||
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| #ifndef _LIBCPP___UTILITY_LAZY_SYNTH_THREE_WAY_COMPARATOR_H | ||
| #define _LIBCPP___UTILITY_LAZY_SYNTH_THREE_WAY_COMPARATOR_H | ||
|
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| #include <__config> | ||
| #include <__type_traits/desugars_to.h> | ||
| #include <__type_traits/enable_if.h> | ||
| #include <__utility/default_three_way_comparator.h> | ||
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| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) | ||
| # pragma GCC system_header | ||
| #endif | ||
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| // This file implements a __lazy_synth_three_way_comparator, which tries to build an efficient three way comparison from | ||
| // a binary comparator. That is done in multiple steps: | ||
| // 1) Check whether the comparator desugars to a less-than operator | ||
| // If that is the case, check whether there exists a specialization of `__default_three_way_comparator`, which | ||
| // can be specialized to implement a three way comparator for the specific types. | ||
| // 2) Fall back to doing a lazy less than/greater than comparison | ||
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| _LIBCPP_BEGIN_NAMESPACE_STD | ||
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| template <class _Comparator, class _LHS, class _RHS> | ||
| struct __lazy_compare_result { | ||
| const _Comparator& __comp_; | ||
| const _LHS& __lhs_; | ||
| const _RHS& __rhs_; | ||
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| _LIBCPP_HIDE_FROM_ABI | ||
| __lazy_compare_result(_LIBCPP_CTOR_LIFETIMEBOUND const _Comparator& __comp, | ||
| _LIBCPP_CTOR_LIFETIMEBOUND const _LHS& __lhs, | ||
| _LIBCPP_CTOR_LIFETIMEBOUND const _RHS& __rhs) | ||
| : __comp_(__comp), __lhs_(__lhs), __rhs_(__rhs) {} | ||
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| _LIBCPP_HIDE_FROM_ABI bool __less() const { return __comp_(__lhs_, __rhs_); } | ||
| _LIBCPP_HIDE_FROM_ABI bool __greater() const { return __comp_(__rhs_, __lhs_); } | ||
| }; | ||
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| // This class provides three way comparison between _LHS and _RHS as efficiently as possible. This can be specialized if | ||
| // a comparator only compares part of the object, potentially allowing an efficient three way comparison between the | ||
| // subobjects. The specialization should use the __lazy_synth_three_way_comparator for the subobjects to achieve this. | ||
| template <class _Comparator, class _LHS, class _RHS, class = void> | ||
| struct __lazy_synth_three_way_comparator { | ||
| const _Comparator& __comp_; | ||
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| _LIBCPP_HIDE_FROM_ABI __lazy_synth_three_way_comparator(_LIBCPP_CTOR_LIFETIMEBOUND const _Comparator& __comp) | ||
| : __comp_(__comp) {} | ||
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| _LIBCPP_HIDE_FROM_ABI __lazy_compare_result<_Comparator, _LHS, _RHS> | ||
| operator()(_LIBCPP_LIFETIMEBOUND const _LHS& __lhs, _LIBCPP_LIFETIMEBOUND const _RHS& __rhs) const { | ||
| return __lazy_compare_result<_Comparator, _LHS, _RHS>(__comp_, __lhs, __rhs); | ||
| } | ||
| }; | ||
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| struct __eager_compare_result { | ||
| int __res_; | ||
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| _LIBCPP_HIDE_FROM_ABI explicit __eager_compare_result(int __res) : __res_(__res) {} | ||
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| _LIBCPP_HIDE_FROM_ABI bool __less() const { return __res_ < 0; } | ||
| _LIBCPP_HIDE_FROM_ABI bool __greater() const { return __res_ > 0; } | ||
| }; | ||
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| template <class _Comparator, class _LHS, class _RHS> | ||
| struct __lazy_synth_three_way_comparator<_Comparator, | ||
| _LHS, | ||
| _RHS, | ||
| __enable_if_t<__desugars_to_v<__less_tag, _Comparator, _LHS, _RHS> && | ||
| __has_default_three_way_comparator_v<_LHS, _RHS> > > { | ||
| // This lifetimebound annotation is technically incorrect, but other specializations actually capture the lifetime of | ||
| // the comparator. | ||
| _LIBCPP_HIDE_FROM_ABI __lazy_synth_three_way_comparator(_LIBCPP_CTOR_LIFETIMEBOUND const _Comparator&) {} | ||
|
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| // Same comment as above. | ||
| _LIBCPP_HIDE_FROM_ABI static __eager_compare_result | ||
| operator()(_LIBCPP_LIFETIMEBOUND const _LHS& __lhs, _LIBCPP_LIFETIMEBOUND const _RHS& __rhs) { | ||
| return __eager_compare_result(__default_three_way_comparator<_LHS, _RHS>()(__lhs, __rhs)); | ||
| } | ||
| }; | ||
|
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| _LIBCPP_END_NAMESPACE_STD | ||
|
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| #endif // _LIBCPP___UTILITY_LAZY_SYNTH_THREE_WAY_COMPARATOR_H |
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