[libcxx-commits] [libcxx] [libc++][NFC] Simplify duration comparisons a bit (PR #201788)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 created https://github.com/llvm/llvm-project/pull/201788

The comparisons have been delegated to a class which has been specialized for the equality case. This has likely been done to avoid `common_type` if possible. However, `common_type` got a lot cheaper, to the point where the classes likely do more harm than good.


>From 7b2b93e0d7ed2180326ed11206eee30f613c3770 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Fri, 5 Jun 2026 10:44:29 +0200
Subject: [PATCH] [libc++][NFC] Simplify duration comparisons a bit

---
 libcxx/include/__chrono/duration.h | 36 ++++--------------------------
 1 file changed, 4 insertions(+), 32 deletions(-)

diff --git a/libcxx/include/__chrono/duration.h b/libcxx/include/__chrono/duration.h
index b7762bd1203ad..4c39ae78c2d68 100644
--- a/libcxx/include/__chrono/duration.h
+++ b/libcxx/include/__chrono/duration.h
@@ -301,25 +301,11 @@ typedef duration<int, ratio<static_cast<int>(365.2425 * 60 * 60 * 24) / 12>> mon
 #endif
 // Duration ==
 
-template <class _LhsDuration, class _RhsDuration>
-struct __duration_eq {
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator()(const _LhsDuration& __lhs, const _RhsDuration& __rhs) const {
-    typedef typename common_type<_LhsDuration, _RhsDuration>::type _Ct;
-    return _Ct(__lhs).count() == _Ct(__rhs).count();
-  }
-};
-
-template <class _LhsDuration>
-struct __duration_eq<_LhsDuration, _LhsDuration> {
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator()(const _LhsDuration& __lhs, const _LhsDuration& __rhs) const {
-    return __lhs.count() == __rhs.count();
-  }
-};
-
 template <class _Rep1, class _Period1, class _Rep2, class _Period2>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
 operator==(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs) {
-  return __duration_eq<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >()(__lhs, __rhs);
+    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Ct;
+    return _Ct(__lhs).count() == _Ct(__rhs).count();
 }
 
 #if _LIBCPP_STD_VER <= 17
@@ -336,25 +322,11 @@ operator!=(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period
 
 // Duration <
 
-template <class _LhsDuration, class _RhsDuration>
-struct __duration_lt {
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator()(const _LhsDuration& __lhs, const _RhsDuration& __rhs) const {
-    typedef typename common_type<_LhsDuration, _RhsDuration>::type _Ct;
-    return _Ct(__lhs).count() < _Ct(__rhs).count();
-  }
-};
-
-template <class _LhsDuration>
-struct __duration_lt<_LhsDuration, _LhsDuration> {
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator()(const _LhsDuration& __lhs, const _LhsDuration& __rhs) const {
-    return __lhs.count() < __rhs.count();
-  }
-};
-
 template <class _Rep1, class _Period1, class _Rep2, class _Period2>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
 operator<(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2>& __rhs) {
-  return __duration_lt<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >()(__lhs, __rhs);
+    typedef typename common_type<duration<_Rep1, _Period1>, duration<_Rep2, _Period2> >::type _Ct;
+    return _Ct(__lhs).count() < _Ct(__rhs).count();
 }
 
 // Duration >