[libcxx-commits] [libcxx] [libc++] Optimize __tree::__find_equal (PR #155245)
via libcxx-commits
libcxx-commits at lists.llvm.org
Mon Aug 25 08:56:06 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: Nikolas Klauser (philnik777)
<details>
<summary>Changes</summary>
```
-----------------------------------------------------------------------------------------------------------------------------
Benchmark old new
-----------------------------------------------------------------------------------------------------------------------------
std::map<int, int>::insert(value) (already present)/0 1.10 ns 1.13 ns
std::map<int, int>::insert(value) (already present)/32 3.63 ns 3.54 ns
std::map<int, int>::insert(value) (already present)/1024 13.2 ns 12.6 ns
std::map<int, int>::insert(value) (already present)/8192 16.9 ns 17.2 ns
std::map<int, int>::insert(value) (new value)/0 21.6 ns 21.9 ns
std::map<int, int>::insert(value) (new value)/32 30.2 ns 29.7 ns
std::map<int, int>::insert(value) (new value)/1024 68.7 ns 76.6 ns
std::map<int, int>::insert(value) (new value)/8192 149 ns 175 ns
std::map<int, int>::insert(hint, value) (good hint)/0 22.0 ns 22.5 ns
std::map<int, int>::insert(hint, value) (good hint)/32 29.7 ns 29.6 ns
std::map<int, int>::insert(hint, value) (good hint)/1024 60.1 ns 58.0 ns
std::map<int, int>::insert(hint, value) (good hint)/8192 112 ns 119 ns
std::map<int, int>::insert(hint, value) (bad hint)/0 21.5 ns 21.8 ns
std::map<int, int>::insert(hint, value) (bad hint)/32 30.4 ns 30.7 ns
std::map<int, int>::insert(hint, value) (bad hint)/1024 78.9 ns 73.4 ns
std::map<int, int>::insert(hint, value) (bad hint)/8192 176 ns 178 ns
std::map<int, int>::insert(iterator, iterator) (all new keys)/0 451 ns 455 ns
std::map<int, int>::insert(iterator, iterator) (all new keys)/32 976 ns 1002 ns
std::map<int, int>::insert(iterator, iterator) (all new keys)/1024 27746 ns 28672 ns
std::map<int, int>::insert(iterator, iterator) (all new keys)/8192 301483 ns 306763 ns
std::map<int, int>::insert(iterator, iterator) (half new keys)/0 451 ns 456 ns
std::map<int, int>::insert(iterator, iterator) (half new keys)/32 774 ns 793 ns
std::map<int, int>::insert(iterator, iterator) (half new keys)/1024 31396 ns 32557 ns
std::map<int, int>::insert(iterator, iterator) (half new keys)/8192 467307 ns 461338 ns
std::map<int, int>::insert(iterator, iterator) (product_iterator from same type)/0 454 ns 457 ns
std::map<int, int>::insert(iterator, iterator) (product_iterator from same type)/32 1025 ns 1037 ns
std::map<int, int>::insert(iterator, iterator) (product_iterator from same type)/1024 29587 ns 30245 ns
std::map<int, int>::insert(iterator, iterator) (product_iterator from same type)/8192 339035 ns 343855 ns
std::map<int, int>::insert(iterator, iterator) (product_iterator from zip_view)/0 452 ns 455 ns
std::map<int, int>::insert(iterator, iterator) (product_iterator from zip_view)/32 948 ns 954 ns
std::map<int, int>::insert(iterator, iterator) (product_iterator from zip_view)/1024 29199 ns 29829 ns
std::map<int, int>::insert(iterator, iterator) (product_iterator from zip_view)/8192 282469 ns 286135 ns
std::map<int, int>::erase(key) (existent)/0 24.7 ns 24.7 ns
std::map<int, int>::erase(key) (existent)/32 31.6 ns 30.0 ns
std::map<int, int>::erase(key) (existent)/1024 51.0 ns 51.1 ns
std::map<int, int>::erase(key) (existent)/8192 65.2 ns 66.9 ns
std::map<int, int>::erase(key) (non-existent)/0 0.327 ns 0.507 ns
std::map<int, int>::erase(key) (non-existent)/32 5.06 ns 4.72 ns
std::map<int, int>::erase(key) (non-existent)/1024 11.1 ns 11.1 ns
std::map<int, int>::erase(key) (non-existent)/8192 16.7 ns 17.0 ns
std::map<int, int>::erase(iterator)/0 24.3 ns 24.0 ns
std::map<int, int>::erase(iterator)/32 24.9 ns 24.4 ns
std::map<int, int>::erase(iterator)/1024 26.3 ns 25.5 ns
std::map<int, int>::erase(iterator)/8192 27.4 ns 26.9 ns
std::map<int, int>::erase(iterator, iterator) (erase half the container)/0 452 ns 453 ns
std::map<int, int>::erase(iterator, iterator) (erase half the container)/32 687 ns 699 ns
std::map<int, int>::erase(iterator, iterator) (erase half the container)/1024 8843 ns 8624 ns
std::map<int, int>::erase(iterator, iterator) (erase half the container)/8192 66617 ns 67326 ns
std::map<int, int>::find(key) (existent)/0 0.007 ns 0.007 ns
std::map<int, int>::find(key) (existent)/32 4.30 ns 4.08 ns
std::map<int, int>::find(key) (existent)/1024 7.41 ns 7.38 ns
std::map<int, int>::find(key) (existent)/8192 11.9 ns 11.8 ns
std::map<int, int>::find(key) (non-existent)/0 0.512 ns 0.305 ns
std::map<int, int>::find(key) (non-existent)/32 4.51 ns 4.61 ns
std::map<int, int>::find(key) (non-existent)/1024 21.4 ns 11.2 ns
std::map<int, int>::find(key) (non-existent)/8192 27.3 ns 16.8 ns
std::map<std::string, int>::insert(value) (already present)/0 14.8 ns 13.7 ns
std::map<std::string, int>::insert(value) (already present)/32 34.0 ns 32.3 ns
std::map<std::string, int>::insert(value) (already present)/1024 54.7 ns 52.0 ns
std::map<std::string, int>::insert(value) (already present)/8192 67.3 ns 67.9 ns
std::map<std::string, int>::insert(value) (new value)/0 42.4 ns 45.2 ns
std::map<std::string, int>::insert(value) (new value)/32 78.1 ns 86.8 ns
std::map<std::string, int>::insert(value) (new value)/1024 158 ns 125 ns
std::map<std::string, int>::insert(value) (new value)/8192 191 ns 161 ns
std::map<std::string, int>::insert(hint, value) (good hint)/0 45.6 ns 57.9 ns
std::map<std::string, int>::insert(hint, value) (good hint)/32 62.1 ns 73.1 ns
std::map<std::string, int>::insert(hint, value) (good hint)/1024 108 ns 120 ns
std::map<std::string, int>::insert(hint, value) (good hint)/8192 134 ns 138 ns
std::map<std::string, int>::insert(hint, value) (bad hint)/0 62.1 ns 41.2 ns
std::map<std::string, int>::insert(hint, value) (bad hint)/32 128 ns 88.1 ns
std::map<std::string, int>::insert(hint, value) (bad hint)/1024 165 ns 134 ns
std::map<std::string, int>::insert(hint, value) (bad hint)/8192 197 ns 184 ns
std::map<std::string, int>::insert(iterator, iterator) (all new keys)/0 457 ns 453 ns
std::map<std::string, int>::insert(iterator, iterator) (all new keys)/32 2435 ns 2128 ns
std::map<std::string, int>::insert(iterator, iterator) (all new keys)/1024 184763 ns 169332 ns
std::map<std::string, int>::insert(iterator, iterator) (all new keys)/8192 1757497 ns 1446335 ns
std::map<std::string, int>::insert(iterator, iterator) (half new keys)/0 457 ns 453 ns
std::map<std::string, int>::insert(iterator, iterator) (half new keys)/32 1997 ns 1587 ns
std::map<std::string, int>::insert(iterator, iterator) (half new keys)/1024 116950 ns 118256 ns
std::map<std::string, int>::insert(iterator, iterator) (half new keys)/8192 1236227 ns 1037691 ns
std::map<std::string, int>::insert(iterator, iterator) (product_iterator from same type)/0 460 ns 455 ns
std::map<std::string, int>::insert(iterator, iterator) (product_iterator from same type)/32 1615 ns 1628 ns
std::map<std::string, int>::insert(iterator, iterator) (product_iterator from same type)/1024 93612 ns 116950 ns
std::map<std::string, int>::insert(iterator, iterator) (product_iterator from same type)/8192 907143 ns 925279 ns
std::map<std::string, int>::insert(iterator, iterator) (product_iterator from zip_view)/0 458 ns 454 ns
std::map<std::string, int>::insert(iterator, iterator) (product_iterator from zip_view)/32 1762 ns 1776 ns
std::map<std::string, int>::insert(iterator, iterator) (product_iterator from zip_view)/1024 117041 ns 105967 ns
std::map<std::string, int>::insert(iterator, iterator) (product_iterator from zip_view)/8192 938247 ns 807760 ns
std::map<std::string, int>::erase(key) (existent)/0 63.7 ns 74.4 ns
std::map<std::string, int>::erase(key) (existent)/32 67.8 ns 99.8 ns
std::map<std::string, int>::erase(key) (existent)/1024 119 ns 114 ns
std::map<std::string, int>::erase(key) (existent)/8192 105 ns 130 ns
std::map<std::string, int>::erase(key) (non-existent)/0 0.309 ns 0.323 ns
std::map<std::string, int>::erase(key) (non-existent)/32 38.4 ns 22.8 ns
std::map<std::string, int>::erase(key) (non-existent)/1024 89.8 ns 53.8 ns
std::map<std::string, int>::erase(key) (non-existent)/8192 121 ns 69.7 ns
std::map<std::string, int>::erase(iterator)/0 36.7 ns 38.7 ns
std::map<std::string, int>::erase(iterator)/32 37.3 ns 37.7 ns
std::map<std::string, int>::erase(iterator)/1024 37.3 ns 38.8 ns
std::map<std::string, int>::erase(iterator)/8192 37.5 ns 38.2 ns
std::map<std::string, int>::erase(iterator, iterator) (erase half the container)/0 444 ns 452 ns
std::map<std::string, int>::erase(iterator, iterator) (erase half the container)/32 788 ns 824 ns
std::map<std::string, int>::erase(iterator, iterator) (erase half the container)/1024 22047 ns 21292 ns
std::map<std::string, int>::erase(iterator, iterator) (erase half the container)/8192 134951 ns 141552 ns
std::map<std::string, int>::find(key) (existent)/0 0.057 ns 0.011 ns
std::map<std::string, int>::find(key) (existent)/32 32.6 ns 19.9 ns
std::map<std::string, int>::find(key) (existent)/1024 59.5 ns 43.7 ns
std::map<std::string, int>::find(key) (existent)/8192 76.6 ns 61.9 ns
std::map<std::string, int>::find(key) (non-existent)/0 0.293 ns 0.338 ns
std::map<std::string, int>::find(key) (non-existent)/32 38.2 ns 24.2 ns
std::map<std::string, int>::find(key) (non-existent)/1024 91.0 ns 54.6 ns
std::map<std::string, int>::find(key) (non-existent)/8192 119 ns 70.6 ns
```
---
Full diff: https://github.com/llvm/llvm-project/pull/155245.diff
6 Files Affected:
- (modified) libcxx/include/CMakeLists.txt (+1)
- (modified) libcxx/include/__tree (+30-2)
- (modified) libcxx/include/__type_traits/enable_if.h (+3)
- (added) libcxx/include/__utility/three_way_comparator.h (+64)
- (modified) libcxx/include/map (+12)
- (modified) libcxx/include/string (+16-1)
``````````diff
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/__type_traits/enable_if.h b/libcxx/include/__type_traits/enable_if.h
index ae1af6ebf17d9..83f721892ac22 100644
--- a/libcxx/include/__type_traits/enable_if.h
+++ b/libcxx/include/__type_traits/enable_if.h
@@ -38,6 +38,9 @@ template <bool _Bp, class _Tp = void>
using enable_if_t = typename enable_if<_Bp, _Tp>::type;
#endif
+template <bool __cond, class _Tp, __enable_if_t<__cond, int> = 0>
+using __enable_specialization_if = _Tp;
+
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___TYPE_TRAITS_ENABLE_IF_H
diff --git a/libcxx/include/__utility/three_way_comparator.h b/libcxx/include/__utility/three_way_comparator.h
new file mode 100644
index 0000000000000..aed6f85de581a
--- /dev/null
+++ b/libcxx/include/__utility/three_way_comparator.h
@@ -0,0 +1,64 @@
+//===----------------------------------------------------------------------===//
+//
+// 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>
+#include <__type_traits/void_t.h>
+#include <__functional/operations.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 __three_way_comparison_traits {};
+
+template <class _Tp>
+struct __three_way_comparison_traits<_Tp, _Tp, __enable_if_t<is_arithmetic<_Tp>::value> > {
+ using __three_way_comparable = void;
+
+ _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 _Comparator, class _LHS, class _RHS, class = void>
+struct __three_way_comparator {};
+
+template <class _Comparator, class _LHS, class _RHS>
+struct __three_way_comparator<_Comparator,
+ _LHS,
+ _RHS,
+ __enable_if_t<__desugars_to_v<__less_tag, _Comparator, _LHS, _RHS>>>
+ : __three_way_comparison_traits<__remove_const_ref_t<_LHS>, __remove_const_ref_t<_RHS>> {};
+
+template <class _Comparator, class _LHS, class _RHS, class = void>
+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,
+ __void_t<typename __three_way_comparator<_Comparator, _LHS, _RHS>::__three_way_comparable>> = true;
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___UTILITY_THREE_WAY_COMPARATOR_H
diff --git a/libcxx/include/map b/libcxx/include/map
index 9bd2282e77a3c..ef044d3000b84 100644
--- a/libcxx/include/map
+++ b/libcxx/include/map
@@ -702,6 +702,18 @@ public:
# endif
};
+template <class _Key, class _CP, class _Compare>
+struct __three_way_comparator<__enable_specialization_if<__has_three_way_comparator_v<_Compare, _Key, _Key>,
+ __map_value_compare<_Key, _CP, _Compare>>,
+ _Key,
+ _CP> : __three_way_comparator<_Compare, _Key, _Key> {
+ using __base = __three_way_comparator<_Compare, _Key, _Key>;
+
+ _LIBCPP_HIDE_FROM_ABI static int operator()(const _Key& __lhs, const _CP& __rhs) {
+ return __base()(__lhs, __rhs.first);
+ }
+};
+
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/string b/libcxx/include/string
index 1d197654b9fee..edfa80162d587 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 +2522,21 @@ _LIBCPP_STRING_V1_EXTERN_TEMPLATE_LIST(_LIBCPP_DECLARE, wchar_t)
# endif
# undef _LIBCPP_DECLARE
+template <class _CharT, class _Traits, class _Alloc>
+struct __three_way_comparison_traits<basic_string<_CharT, _Traits, _Alloc>, basic_string<_CharT, _Traits, _Alloc>> {
+ using __string_t = basic_string<_CharT, _Traits, _Alloc>;
+
+ using __three_way_comparable = void;
+
+ _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>,
``````````
</details>
https://github.com/llvm/llvm-project/pull/155245
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