[libcxx-commits] [libcxx] [libc++] Simplify std::equal a bit (PR #171585)
Nikolas Klauser via libcxx-commits
libcxx-commits at lists.llvm.org
Thu Dec 11 06:02:26 PST 2025
https://github.com/philnik777 updated https://github.com/llvm/llvm-project/pull/171585
>From d7cdd49d4238054e874adbabb0ef7e449d7a3f5f Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Tue, 9 Dec 2025 12:21:52 +0100
Subject: [PATCH] [libc++] Simplify std::equal a bit
This is also a prerequisite for optimizing `std::search`.
---
libcxx/include/__algorithm/equal.h | 96 ++++++++-----------
libcxx/include/__algorithm/ranges_equal.h | 45 ++++-----
libcxx/include/__bit_reference | 16 +++-
.../memory/specialized.algorithms/buffer.h | 2 +-
4 files changed, 74 insertions(+), 85 deletions(-)
diff --git a/libcxx/include/__algorithm/equal.h b/libcxx/include/__algorithm/equal.h
index 5a8c9504ede1d..63df043263cbe 100644
--- a/libcxx/include/__algorithm/equal.h
+++ b/libcxx/include/__algorithm/equal.h
@@ -160,22 +160,28 @@ template <class _Cp,
bool _IsConst1,
bool _IsConst2,
class _BinaryPredicate,
- __enable_if_t<__desugars_to_v<__equal_tag, _BinaryPredicate, bool, bool>, int> = 0>
+ class _Proj1,
+ class _Proj2,
+ __enable_if_t<__is_identity<_Proj1>::value && __is_identity<_Proj2>::value &&
+ __desugars_to_v<__equal_tag, _BinaryPredicate, bool, bool>,
+ int> = 0>
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __equal_iter_impl(
__bit_iterator<_Cp, _IsConst1> __first1,
__bit_iterator<_Cp, _IsConst1> __last1,
__bit_iterator<_Cp, _IsConst2> __first2,
- _BinaryPredicate) {
+ _BinaryPredicate,
+ _Proj1&,
+ _Proj2&) {
if (__first1.__ctz_ == __first2.__ctz_)
return std::__equal_aligned(__first1, __last1, __first2);
return std::__equal_unaligned(__first1, __last1, __first2);
}
-template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
+template <class _InIter1, class _Sent1, class _InIter2, class _Pred, class _Proj1, class _Proj2>
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __equal_iter_impl(
- _InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _BinaryPredicate& __pred) {
+ _InIter1 __first1, _Sent1 __last1, _InIter2 __first2, _Pred& __pred, _Proj1& __proj1, _Proj2& __proj2) {
for (; __first1 != __last1; ++__first1, (void)++__first2)
- if (!__pred(*__first1, *__first2))
+ if (!std::__invoke(__pred, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
return false;
return true;
}
@@ -183,19 +189,23 @@ template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
template <class _Tp,
class _Up,
class _BinaryPredicate,
- __enable_if_t<__desugars_to_v<__equal_tag, _BinaryPredicate, _Tp, _Up> && !is_volatile<_Tp>::value &&
+ class _Proj1,
+ class _Proj2,
+ __enable_if_t<__is_identity<_Proj1>::value && __is_identity<_Proj2>::value &&
+ __desugars_to_v<__equal_tag, _BinaryPredicate, _Tp, _Up> && !is_volatile<_Tp>::value &&
!is_volatile<_Up>::value && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value,
int> = 0>
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
-__equal_iter_impl(_Tp* __first1, _Tp* __last1, _Up* __first2, _BinaryPredicate&) {
+__equal_iter_impl(_Tp* __first1, _Tp* __last1, _Up* __first2, _BinaryPredicate&, _Proj1&, _Proj2&) {
return std::__constexpr_memcmp_equal(__first1, __first2, __element_count(__last1 - __first1));
}
template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
equal(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _BinaryPredicate __pred) {
+ __identity __proj;
return std::__equal_iter_impl(
- std::__unwrap_iter(__first1), std::__unwrap_iter(__last1), std::__unwrap_iter(__first2), __pred);
+ std::__unwrap_iter(__first1), std::__unwrap_iter(__last1), std::__unwrap_iter(__first2), __pred, __proj, __proj);
}
template <class _InputIterator1, class _InputIterator2>
@@ -206,52 +216,28 @@ equal(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first
#if _LIBCPP_STD_VER >= 14
-template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class _Pred, class _Proj1, class _Proj2>
-[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __equal_impl(
- _Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2, _Pred& __comp, _Proj1& __proj1, _Proj2& __proj2) {
- while (__first1 != __last1 && __first2 != __last2) {
- if (!std::__invoke(__comp, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
- return false;
- ++__first1;
- ++__first2;
- }
- return __first1 == __last1 && __first2 == __last2;
-}
-
-template <class _Tp,
- class _Up,
- class _Pred,
- class _Proj1,
- class _Proj2,
- __enable_if_t<__desugars_to_v<__equal_tag, _Pred, _Tp, _Up> && __is_identity<_Proj1>::value &&
- __is_identity<_Proj2>::value && !is_volatile<_Tp>::value && !is_volatile<_Up>::value &&
- __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value,
- int> = 0>
-[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
-__equal_impl(_Tp* __first1, _Tp* __last1, _Up* __first2, _Up*, _Pred&, _Proj1&, _Proj2&) {
- return std::__constexpr_memcmp_equal(__first1, __first2, __element_count(__last1 - __first1));
-}
-
-template <class _Cp,
- bool _IsConst1,
- bool _IsConst2,
+template <bool __known_equal_length,
+ class _Iter1,
+ class _Sent1,
+ class _Iter2,
+ class _Sent2,
class _Pred,
class _Proj1,
- class _Proj2,
- __enable_if_t<__desugars_to_v<__equal_tag, _Pred, bool, bool> && __is_identity<_Proj1>::value &&
- __is_identity<_Proj2>::value,
- int> = 0>
+ class _Proj2>
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __equal_impl(
- __bit_iterator<_Cp, _IsConst1> __first1,
- __bit_iterator<_Cp, _IsConst1> __last1,
- __bit_iterator<_Cp, _IsConst2> __first2,
- __bit_iterator<_Cp, _IsConst2>,
- _Pred&,
- _Proj1&,
- _Proj2&) {
- if (__first1.__ctz_ == __first2.__ctz_)
- return std::__equal_aligned(__first1, __last1, __first2);
- return std::__equal_unaligned(__first1, __last1, __first2);
+ _Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2, _Pred& __comp, _Proj1& __proj1, _Proj2& __proj2) {
+ if constexpr (__known_equal_length) {
+ return std::__equal_iter_impl(
+ std::move(__first1), std::move(__last1), std::move(__first2), __comp, __proj1, __proj2);
+ } else {
+ while (__first1 != __last1 && __first2 != __last2) {
+ if (!std::__invoke(__comp, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
+ return false;
+ ++__first1;
+ ++__first2;
+ }
+ return __first1 == __last1 && __first2 == __last2;
+ }
}
template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
@@ -261,13 +247,15 @@ equal(_InputIterator1 __first1,
_InputIterator2 __first2,
_InputIterator2 __last2,
_BinaryPredicate __pred) {
- if constexpr (__has_random_access_iterator_category<_InputIterator1>::value &&
- __has_random_access_iterator_category<_InputIterator2>::value) {
+ static constexpr bool __both_random_access =
+ __has_random_access_iterator_category<_InputIterator1>::value &&
+ __has_random_access_iterator_category<_InputIterator2>::value;
+ if constexpr (__both_random_access) {
if (std::distance(__first1, __last1) != std::distance(__first2, __last2))
return false;
}
__identity __proj;
- return std::__equal_impl(
+ return std::__equal_impl<__both_random_access>(
std::__unwrap_iter(__first1),
std::__unwrap_iter(__last1),
std::__unwrap_iter(__first2),
diff --git a/libcxx/include/__algorithm/ranges_equal.h b/libcxx/include/__algorithm/ranges_equal.h
index c26d13f002201..300ff13faf711 100644
--- a/libcxx/include/__algorithm/ranges_equal.h
+++ b/libcxx/include/__algorithm/ranges_equal.h
@@ -13,13 +13,12 @@
#include <__algorithm/unwrap_range.h>
#include <__config>
#include <__functional/identity.h>
-#include <__functional/invoke.h>
#include <__functional/ranges_operations.h>
#include <__iterator/concepts.h>
-#include <__iterator/distance.h>
#include <__iterator/indirectly_comparable.h>
#include <__ranges/access.h>
#include <__ranges/concepts.h>
+#include <__ranges/size.h>
#include <__utility/move.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -35,6 +34,8 @@ _LIBCPP_BEGIN_NAMESPACE_STD
namespace ranges {
struct __equal {
+
+
template <input_iterator _Iter1,
sentinel_for<_Iter1> _Sent1,
input_iterator _Iter2,
@@ -51,20 +52,15 @@ struct __equal {
_Pred __pred = {},
_Proj1 __proj1 = {},
_Proj2 __proj2 = {}) const {
- if constexpr (sized_sentinel_for<_Sent1, _Iter1> && sized_sentinel_for<_Sent2, _Iter2>) {
- if (__last1 - __first1 != __last2 - __first2)
+ auto [__ufirst1, __ulast1] = std::__unwrap_range(std::move(__first1), std::move(__last1));
+ auto [__ufirst2, __ulast2] = std::__unwrap_range(std::move(__first2), std::move(__last2));
+ static constexpr bool __both_sized = sized_sentinel_for<_Sent1, _Iter1> && sized_sentinel_for<_Sent2, _Iter2>;
+ if constexpr (__both_sized) {
+ if (__ulast1 - __ufirst1 != __ulast2 - __ufirst2)
return false;
}
- auto __unwrapped1 = std::__unwrap_range(std::move(__first1), std::move(__last1));
- auto __unwrapped2 = std::__unwrap_range(std::move(__first2), std::move(__last2));
- return std::__equal_impl(
- std::move(__unwrapped1.first),
- std::move(__unwrapped1.second),
- std::move(__unwrapped2.first),
- std::move(__unwrapped2.second),
- __pred,
- __proj1,
- __proj2);
+ return std::__equal_impl<__both_sized>(
+ std::move(__ufirst1), std::move(__ulast1), std::move(__ufirst2), std::move(__ulast2), __pred, __proj1, __proj2);
}
template <input_range _Range1,
@@ -75,21 +71,16 @@ struct __equal {
requires indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>, _Pred, _Proj1, _Proj2>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(
_Range1&& __range1, _Range2&& __range2, _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
- if constexpr (sized_range<_Range1> && sized_range<_Range2>) {
- if (ranges::distance(__range1) != ranges::distance(__range2))
+ static constexpr bool __both_sized = sized_range<_Range1> && sized_range<_Range2>;
+ if constexpr (__both_sized) {
+ if (ranges::size(__range1) != ranges::size(__range2))
return false;
}
- auto __unwrapped1 = std::__unwrap_range(ranges::begin(__range1), ranges::end(__range1));
- auto __unwrapped2 = std::__unwrap_range(ranges::begin(__range2), ranges::end(__range2));
- return std::__equal_impl(
- std::move(__unwrapped1.first),
- std::move(__unwrapped1.second),
- std::move(__unwrapped2.first),
- std::move(__unwrapped2.second),
- __pred,
- __proj1,
- __proj2);
- return false;
+
+ auto [__ufirst1, __ulast1] = std::__unwrap_range(ranges::begin(__range1), ranges::end(__range1));
+ auto [__ufirst2, __ulast2] = std::__unwrap_range(ranges::begin(__range2), ranges::end(__range2));
+ return std::__equal_impl<__both_sized>(
+ std::move(__ufirst1), std::move(__ulast1), std::move(__ufirst2), std::move(__ulast2), __pred, __proj1, __proj2);
}
};
diff --git a/libcxx/include/__bit_reference b/libcxx/include/__bit_reference
index 00bbc4100ddb9..082a0575ee7dc 100644
--- a/libcxx/include/__bit_reference
+++ b/libcxx/include/__bit_reference
@@ -509,10 +509,20 @@ private:
bool _IsConst1,
bool _IsConst2,
class _BinaryPredicate,
- __enable_if_t<__desugars_to_v<__equal_tag, _BinaryPredicate, bool, bool>, int> >
+ class _Proj1,
+ class _Proj2,
+ __enable_if_t<__is_identity<_Proj1>::value && __is_identity<_Proj2>::value &&
+ __desugars_to_v<__equal_tag, _BinaryPredicate, bool, bool>,
+ int> >
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 friend bool __equal_iter_impl(
- __bit_iterator<_Dp, _IsConst1>, __bit_iterator<_Dp, _IsConst1>, __bit_iterator<_Dp, _IsConst2>, _BinaryPredicate);
- template <class _Dp,
+ __bit_iterator<_Dp, _IsConst1>,
+ __bit_iterator<_Dp, _IsConst1>,
+ __bit_iterator<_Dp, _IsConst2>,
+ _BinaryPredicate,
+ _Proj1&,
+ _Proj2&);
+ template <bool,
+ class _Dp,
bool _IsConst1,
bool _IsConst2,
class _Pred,
diff --git a/libcxx/test/std/utilities/memory/specialized.algorithms/buffer.h b/libcxx/test/std/utilities/memory/specialized.algorithms/buffer.h
index 1114fdc68e724..072c0546cd7be 100644
--- a/libcxx/test/std/utilities/memory/specialized.algorithms/buffer.h
+++ b/libcxx/test/std/utilities/memory/specialized.algorithms/buffer.h
@@ -19,7 +19,7 @@ struct Buffer {
const T* cbegin() const { return reinterpret_cast<const T*>(buffer); }
const T* cend() const { return cbegin() + N; }
- constexpr int size() const { return N; }
+ constexpr unsigned size() const { return N; }
};
#endif // LIBCPP_TEST_STD_UTILITIES_MEMORY_SPECIALIZED_ALGORITHMS_BUFFER_H
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