[libcxx-commits] [libcxx] [libc++] Optimize __tree::__find_equal (PR #155245)
Nikolas Klauser via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Aug 26 01:32:37 PDT 2025
https://github.com/philnik777 updated https://github.com/llvm/llvm-project/pull/155245
>From 3bcef680975ef61a754697113e675a49aca7bb35 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Fri, 22 Aug 2025 10:39:37 +0200
Subject: [PATCH] [libc++] Optimize __tree::__find_equal
---
libcxx/include/CMakeLists.txt | 1 +
libcxx/include/__tree | 32 ++++++++-
.../include/__utility/three_way_comparator.h | 71 +++++++++++++++++++
libcxx/include/map | 30 ++++++++
libcxx/include/module.modulemap.in | 1 +
libcxx/include/string | 15 +++-
6 files changed, 147 insertions(+), 3 deletions(-)
create mode 100644 libcxx/include/__utility/three_way_comparator.h
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index c6b87a34a43e9..acda31701adf3 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -932,6 +932,7 @@ set(files
__utility/scope_guard.h
__utility/small_buffer.h
__utility/swap.h
+ __utility/three_way_comparator.h
__utility/to_underlying.h
__utility/unreachable.h
__variant/monostate.h
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
index 0f3640ef6a834..670e28cbb8d2b 100644
--- a/libcxx/include/__tree
+++ b/libcxx/include/__tree
@@ -38,6 +38,7 @@
#include <__utility/move.h>
#include <__utility/pair.h>
#include <__utility/swap.h>
+#include <__utility/three_way_comparator.h>
#include <limits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -1711,7 +1712,34 @@ __tree<_Tp, _Compare, _Allocator>::__find_equal(__end_node_pointer& __parent, co
__node_base_pointer* __nd_ptr = __root_ptr();
if (__nd != nullptr) {
while (true) {
- if (value_comp()(__v, __nd->__get_value())) {
+#ifndef _LIBCPP_CXX03_LANG
+ static const bool __use_three_way = __has_three_way_comparator_v<_Compare, _Key, value_type>;
+
+ int __comp_res;
+ if constexpr (__use_three_way) {
+ __comp_res = __three_way_comparator<_Compare, _Key, value_type>()(__v, __nd->__get_value());
+ }
+#endif
+
+ auto __less = [&] {
+#ifndef _LIBCPP_CXX03_LANG
+ if constexpr (__use_three_way)
+ return __comp_res < 0;
+ else
+#endif
+ return value_comp()(__v, __nd->__get_value());
+ };
+
+ auto __greater = [&] {
+#ifndef _LIBCPP_CXX03_LANG
+ if constexpr (__use_three_way)
+ return __comp_res > 0;
+ else
+#endif
+ return value_comp()(__nd->__get_value(), __v);
+ };
+
+ if (__less()) {
if (__nd->__left_ != nullptr) {
__nd_ptr = std::addressof(__nd->__left_);
__nd = static_cast<__node_pointer>(__nd->__left_);
@@ -1719,7 +1747,7 @@ __tree<_Tp, _Compare, _Allocator>::__find_equal(__end_node_pointer& __parent, co
__parent = static_cast<__end_node_pointer>(__nd);
return __parent->__left_;
}
- } else if (value_comp()(__nd->__get_value(), __v)) {
+ } else if (__greater()) {
if (__nd->__right_ != nullptr) {
__nd_ptr = std::addressof(__nd->__right_);
__nd = static_cast<__node_pointer>(__nd->__right_);
diff --git a/libcxx/include/__utility/three_way_comparator.h b/libcxx/include/__utility/three_way_comparator.h
new file mode 100644
index 0000000000000..ec45e5b844d85
--- /dev/null
+++ b/libcxx/include/__utility/three_way_comparator.h
@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___UTILITY_THREE_WAY_COMPARATOR_H
+#define _LIBCPP___UTILITY_THREE_WAY_COMPARATOR_H
+
+#include <__config>
+#include <__type_traits/desugars_to.h>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_arithmetic.h>
+#include <__type_traits/remove_const_ref.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _LHS, class _RHS, class = void>
+struct __default_three_way_comparator;
+
+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;
+ }
+};
+
+template <class _LHS, class _RHS, bool = true>
+inline const bool __has_default_three_way_comparator_v = false;
+
+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;
+
+template <class _Comparator, class _LHS, class _RHS, class = void>
+struct __three_way_comparator_impl;
+
+template <class _Comparator, class _LHS, class _RHS>
+struct __three_way_comparator_impl<_Comparator,
+ _LHS,
+ _RHS,
+ __enable_if_t<__desugars_to_v<__less_tag, _Comparator, _LHS, _RHS> &&
+ __has_default_three_way_comparator_v<_LHS, _RHS>>>
+ : __default_three_way_comparator<_LHS, _RHS> {};
+
+template <class _Comparator, class _LHS, class _RHS>
+using __three_way_comparator _LIBCPP_NODEBUG =
+ __three_way_comparator_impl<_Comparator, __remove_const_ref_t<_LHS>, __remove_const_ref_t<_RHS>>;
+
+template <class _Comparator, class _LHS, class _RHS, bool = true>
+inline const bool __has_three_way_comparator_v = false;
+
+template <class _Comparator, class _LHS, class _RHS>
+inline const bool __has_three_way_comparator_v<_Comparator,
+ _LHS,
+ _RHS,
+ sizeof(__three_way_comparator<_Comparator, _LHS, _RHS>) >= 0> = true;
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___UTILITY_THREE_WAY_COMPARATOR_H
diff --git a/libcxx/include/map b/libcxx/include/map
index 9bd2282e77a3c..c22527c7abf97 100644
--- a/libcxx/include/map
+++ b/libcxx/include/map
@@ -702,6 +702,36 @@ public:
# endif
};
+template <class _CP, class _Key, class _Compare>
+struct __three_way_comparator_impl<__map_value_compare<_Key, _CP, _Compare>,
+ _CP,
+ _CP,
+ __enable_if_t<__has_three_way_comparator_v<_Compare, _Key, _Key> > > {
+ _LIBCPP_HIDE_FROM_ABI static int operator()(const _CP& __lhs, const _CP& __rhs) {
+ return __three_way_comparator<_Compare, _Key, _Key>()(__lhs.first, __rhs.first);
+ }
+};
+
+template <class _CP, class _Key, class _Key2, class _Compare>
+struct __three_way_comparator_impl<__map_value_compare<_Key, _CP, _Compare>,
+ _Key2,
+ _CP,
+ __enable_if_t<__has_three_way_comparator_v<_Compare, _Key2, _Key> > > {
+ _LIBCPP_HIDE_FROM_ABI static int operator()(const _Key2& __lhs, const _CP& __rhs) {
+ return __three_way_comparator<_Compare, _Key, _Key>()(__lhs, __rhs.first);
+ }
+};
+
+template <class _CP, class _Key, class _Key2, class _Compare>
+struct __three_way_comparator_impl<__map_value_compare<_Key, _CP, _Compare>,
+ _CP,
+ _Key2,
+ __enable_if_t<__has_three_way_comparator_v<_Compare, _Key, _Key2> > > {
+ _LIBCPP_HIDE_FROM_ABI static int operator()(const _CP& __lhs, const _Key2& __rhs) {
+ return __three_way_comparator<_Compare, _Key, _Key>()(__lhs.first, __rhs);
+ }
+};
+
template <class _Key, class _CP, class _Compare, bool __b>
inline _LIBCPP_HIDE_FROM_ABI void
swap(__map_value_compare<_Key, _CP, _Compare, __b>& __x, __map_value_compare<_Key, _CP, _Compare, __b>& __y)
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index c431c0cb407f3..9aa3088b28c2c 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -2177,6 +2177,7 @@ module std [system] {
module scope_guard { header "__utility/scope_guard.h" }
module small_buffer { header "__utility/small_buffer.h" }
module swap { header "__utility/swap.h" }
+ module three_way_comparator { header "__utility/three_way_comparator.h" }
module to_underlying { header "__utility/to_underlying.h" }
module unreachable { header "__utility/unreachable.h" }
diff --git a/libcxx/include/string b/libcxx/include/string
index 1d197654b9fee..4cee578b8a49f 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -645,7 +645,7 @@ basic_string<char32_t> operator""s( const char32_t *str, size_t len );
# include <__utility/move.h>
# include <__utility/scope_guard.h>
# include <__utility/swap.h>
-# include <__utility/unreachable.h>
+# include <__utility/three_way_comparator.h>
# include <climits>
# include <cstdio> // EOF
# include <cstring>
@@ -2522,6 +2522,19 @@ _LIBCPP_STRING_V1_EXTERN_TEMPLATE_LIST(_LIBCPP_DECLARE, wchar_t)
# endif
# undef _LIBCPP_DECLARE
+template <class _CharT, class _Traits, class _Alloc>
+struct __default_three_way_comparator<basic_string<_CharT, _Traits, _Alloc>, basic_string<_CharT, _Traits, _Alloc>> {
+ using __string_t _LIBCPP_NODEBUG = basic_string<_CharT, _Traits, _Alloc>;
+
+ _LIBCPP_HIDE_FROM_ABI static int operator()(const __string_t& __lhs, const __string_t& __rhs) {
+ auto __min_len = std::min(__lhs.size(), __rhs.size());
+ auto __ret = _Traits::compare(__lhs.data(), __rhs.data(), __min_len);
+ if (__ret == 0)
+ return __lhs.size() == __rhs.size() ? 0 : __lhs.size() < __rhs.size() ? -1 : 1;
+ return __ret;
+ }
+};
+
# if _LIBCPP_STD_VER >= 17
template <class _InputIterator,
class _CharT = __iter_value_type<_InputIterator>,
More information about the libcxx-commits
mailing list