Revert "[libc++] Avoid constructing additional objects when using map::at (#1…"

alazarev · web-flow · commit 061cd0de555b · 2025-09-25T10:01:35.000-07:00
This reverts commit 833d5f0.
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
@@ -839,7 +839,6 @@ set(files
   __type_traits/is_floating_point.h
   __type_traits/is_function.h
   __type_traits/is_fundamental.h
-  __type_traits/is_generic_transparent_comparator.h
   __type_traits/is_implicit_lifetime.h
   __type_traits/is_implicitly_default_constructible.h
   __type_traits/is_integral.h
@@ -882,7 +881,6 @@ set(files
   __type_traits/make_32_64_or_128_bit.h
   __type_traits/make_const_lvalue_ref.h
   __type_traits/make_signed.h
-  __type_traits/make_transparent.h
   __type_traits/make_unsigned.h
   __type_traits/maybe_const.h
   __type_traits/nat.h
diff --git a/libcxx/include/__algorithm/comp.h b/libcxx/include/__algorithm/comp.h
@@ -11,7 +11,6 @@
 
 #include <__config>
 #include <__type_traits/desugars_to.h>
-#include <__type_traits/is_generic_transparent_comparator.h>
 #include <__type_traits/is_integral.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -49,9 +48,6 @@ inline const bool __desugars_to_v<__less_tag, __less<>, _Tp, _Tp> = true;
 template <class _Tp>
 inline const bool __desugars_to_v<__totally_ordered_less_tag, __less<>, _Tp, _Tp> = is_integral<_Tp>::value;
 
-template <>
-inline const bool __is_generic_transparent_comparator_v<__less<> > = true;
-
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_COMP_H
diff --git a/libcxx/include/__functional/is_transparent.h b/libcxx/include/__functional/is_transparent.h
@@ -29,14 +29,6 @@ inline const bool __is_transparent_v<_Tp, _Key, __void_t<typename _Tp::is_transp
 
 #endif
 
-// Two types are considered transparently comparable if `comparator(key, arg)` is equivalent to `comparator(key,
-// <implicit cast to KeyT>(arg))`.
-//
-// This is different from `__is_transparent_v`, which is only a property of the comparator and doesn't provide
-// additional semantic guarantees.
-template <class _Comparator, class _KeyT, class _Arg, class = void>
-inline const bool __is_transparently_comparable_v = false;
-
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___FUNCTIONAL_IS_TRANSPARENT
diff --git a/libcxx/include/__functional/operations.h b/libcxx/include/__functional/operations.h
@@ -15,9 +15,7 @@
 #include <__functional/unary_function.h>
 #include <__fwd/functional.h>
 #include <__type_traits/desugars_to.h>
-#include <__type_traits/is_generic_transparent_comparator.h>
 #include <__type_traits/is_integral.h>
-#include <__type_traits/make_transparent.h>
 #include <__utility/forward.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -379,14 +377,6 @@ struct less<void> {
   typedef void is_transparent;
 };
 
-template <class _Tp>
-struct __make_transparent<less<_Tp> > {
-  using type _LIBCPP_NODEBUG = less<>;
-};
-
-template <>
-inline const bool __is_generic_transparent_comparator_v<less<>> = true;
-
 template <class _Tp, class _Up>
 inline const bool __desugars_to_v<__less_tag, less<>, _Tp, _Up> = true;
 
@@ -476,14 +466,6 @@ struct greater<void> {
 
 template <class _Tp, class _Up>
 inline const bool __desugars_to_v<__greater_tag, greater<>, _Tp, _Up> = true;
-
-template <class _Tp>
-struct __make_transparent<greater<_Tp>> {
-  using type _LIBCPP_NODEBUG = greater<>;
-};
-
-template <>
-inline const bool __is_generic_transparent_comparator_v<greater<>> = true;
 #endif
 
 // Logical operations
diff --git a/libcxx/include/__functional/ranges_operations.h b/libcxx/include/__functional/ranges_operations.h
@@ -14,7 +14,6 @@
 #include <__concepts/totally_ordered.h>
 #include <__config>
 #include <__type_traits/desugars_to.h>
-#include <__type_traits/is_generic_transparent_comparator.h>
 #include <__utility/forward.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -109,12 +108,6 @@ inline const bool __desugars_to_v<__less_tag, ranges::less, _Tp, _Up> = true;
 template <class _Tp, class _Up>
 inline const bool __desugars_to_v<__greater_tag, ranges::greater, _Tp, _Up> = true;
 
-template <>
-inline const bool __is_generic_transparent_comparator_v<ranges::less> = true;
-
-template <>
-inline const bool __is_generic_transparent_comparator_v<ranges::greater> = true;
-
 #endif // _LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
@@ -34,7 +34,6 @@
 #include <__type_traits/is_same.h>
 #include <__type_traits/is_specialization.h>
 #include <__type_traits/is_swappable.h>
-#include <__type_traits/make_transparent.h>
 #include <__type_traits/remove_const.h>
 #include <__utility/forward.h>
 #include <__utility/lazy_synth_three_way_comparator.h>
@@ -1750,8 +1749,7 @@ __tree<_Tp, _Compare, _Allocator>::__find_equal(const _Key& __v) {
   }
 
   __node_base_pointer* __node_ptr = __root_ptr();
-  auto&& __transparent            = std::__as_transparent(value_comp());
-  auto __comp = __lazy_synth_three_way_comparator<__make_transparent_t<_Compare>, _Key, value_type>(__transparent);
+  auto __comp                     = __lazy_synth_three_way_comparator<_Compare, _Key, value_type>(value_comp());
 
   while (true) {
     auto __comp_res = __comp(__v, __nd->__get_value());
diff --git a/libcxx/include/__type_traits/is_generic_transparent_comparator.h b/libcxx/include/__type_traits/is_generic_transparent_comparator.h
diff --git a/libcxx/include/__type_traits/make_transparent.h b/libcxx/include/__type_traits/make_transparent.h
diff --git a/libcxx/include/map b/libcxx/include/map
@@ -600,10 +600,7 @@ erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred);  // C++20
 #  include <__ranges/from_range.h>
 #  include <__tree>
 #  include <__type_traits/container_traits.h>
-#  include <__type_traits/desugars_to.h>
 #  include <__type_traits/is_allocator.h>
-#  include <__type_traits/is_convertible.h>
-#  include <__type_traits/make_transparent.h>
 #  include <__type_traits/remove_const.h>
 #  include <__type_traits/type_identity.h>
 #  include <__utility/forward.h>
@@ -669,11 +666,6 @@ public:
 #  endif
 };
 
-template <class _Key, class _MapValueT, class _Compare>
-struct __make_transparent<__map_value_compare<_Key, _MapValueT, _Compare> > {
-  using type _LIBCPP_NODEBUG = __map_value_compare<_Key, _MapValueT, __make_transparent_t<_Compare> >;
-};
-
 #  if _LIBCPP_STD_VER >= 14
 template <class _MapValueT, class _Key, class _Compare>
 struct __lazy_synth_three_way_comparator<__map_value_compare<_Key, _MapValueT, _Compare>, _MapValueT, _MapValueT> {
@@ -1056,24 +1048,6 @@ public:
   _LIBCPP_HIDE_FROM_ABI mapped_type& operator[](key_type&& __k);
 #  endif
 
-  template <class _Arg,
-            __enable_if_t<__is_transparently_comparable_v<_Compare, key_type, __remove_cvref_t<_Arg> >, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI mapped_type& at(_Arg&& __arg) {
-    auto [_, __child] = __tree_.__find_equal(__arg);
-    if (__child == nullptr)
-      std::__throw_out_of_range("map::at:  key not found");
-    return static_cast<__node_pointer>(__child)->__get_value().second;
-  }
-
-  template <class _Arg,
-            __enable_if_t<__is_transparently_comparable_v<_Compare, key_type, __remove_cvref_t<_Arg> >, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI const mapped_type& at(_Arg&& __arg) const {
-    auto [_, __child] = __tree_.__find_equal(__arg);
-    if (__child == nullptr)
-      std::__throw_out_of_range("map::at:  key not found");
-    return static_cast<__node_pointer>(__child)->__get_value().second;
-  }
-
   _LIBCPP_HIDE_FROM_ABI mapped_type& at(const key_type& __k);
   _LIBCPP_HIDE_FROM_ABI const mapped_type& at(const key_type& __k) const;
 
@@ -1268,15 +1242,11 @@ public:
   _LIBCPP_HIDE_FROM_ABI iterator find(const key_type& __k) { return __tree_.find(__k); }
   _LIBCPP_HIDE_FROM_ABI const_iterator find(const key_type& __k) const { return __tree_.find(__k); }
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2,
-            enable_if_t<__is_transparent_v<_Compare, _K2> || __is_transparently_comparable_v<_Compare, key_type, _K2>,
-                        int> = 0>
+  template <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, int> = 0>
   _LIBCPP_HIDE_FROM_ABI iterator find(const _K2& __k) {
     return __tree_.find(__k);
   }
-  template <typename _K2,
-            enable_if_t<__is_transparent_v<_Compare, _K2> || __is_transparently_comparable_v<_Compare, key_type, _K2>,
-                        int> = 0>
+  template <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, int> = 0>
   _LIBCPP_HIDE_FROM_ABI const_iterator find(const _K2& __k) const {
     return __tree_.find(__k);
   }
@@ -1292,9 +1262,7 @@ public:
 
 #  if _LIBCPP_STD_VER >= 20
   _LIBCPP_HIDE_FROM_ABI bool contains(const key_type& __k) const { return find(__k) != end(); }
-  template <typename _K2,
-            enable_if_t<__is_transparent_v<_Compare, _K2> || __is_transparently_comparable_v<_Compare, key_type, _K2>,
-                        int> = 0>
+  template <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, int> = 0>
   _LIBCPP_HIDE_FROM_ABI bool contains(const _K2& __k) const {
     return find(__k) != end();
   }
@@ -1303,16 +1271,12 @@ public:
   _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const key_type& __k) { return __tree_.lower_bound(__k); }
   _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const key_type& __k) const { return __tree_.lower_bound(__k); }
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2,
-            enable_if_t<__is_transparent_v<_Compare, _K2> || __is_transparently_comparable_v<_Compare, key_type, _K2>,
-                        int> = 0>
+  template <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, int> = 0>
   _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const _K2& __k) {
     return __tree_.lower_bound(__k);
   }
 
-  template <typename _K2,
-            enable_if_t<__is_transparent_v<_Compare, _K2> || __is_transparently_comparable_v<_Compare, key_type, _K2>,
-                        int> = 0>
+  template <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, int> = 0>
   _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const _K2& __k) const {
     return __tree_.lower_bound(__k);
   }
@@ -1321,15 +1285,11 @@ public:
   _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const key_type& __k) { return __tree_.upper_bound(__k); }
   _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const key_type& __k) const { return __tree_.upper_bound(__k); }
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2,
-            enable_if_t<__is_transparent_v<_Compare, _K2> || __is_transparently_comparable_v<_Compare, key_type, _K2>,
-                        int> = 0>
+  template <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, int> = 0>
   _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const _K2& __k) {
     return __tree_.upper_bound(__k);
   }
-  template <typename _K2,
-            enable_if_t<__is_transparent_v<_Compare, _K2> || __is_transparently_comparable_v<_Compare, key_type, _K2>,
-                        int> = 0>
+  template <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, int> = 0>
   _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const _K2& __k) const {
     return __tree_.upper_bound(__k);
   }
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
@@ -200,7 +200,6 @@ module std_core [system] {
       header "__type_traits/is_fundamental.h"
       export std_core.type_traits.integral_constant
     }
-    module is_generic_transparent_comparator { header "__type_traits/is_generic_transparent_comparator.h" }
     module is_implicit_lifetime {
       header "__type_traits/is_implicit_lifetime.h"
       export std_core.type_traits.integral_constant
@@ -354,7 +353,6 @@ module std_core [system] {
     module make_32_64_or_128_bit                      { header "__type_traits/make_32_64_or_128_bit.h" }
     module make_const_lvalue_ref                      { header "__type_traits/make_const_lvalue_ref.h" }
     module make_signed                                { header "__type_traits/make_signed.h" }
-    module make_transparent                           { header "__type_traits/make_transparent.h" }
     module make_unsigned                              { header "__type_traits/make_unsigned.h" }
     module maybe_const                                { header "__type_traits/maybe_const.h" }
     module nat                                        { header "__type_traits/nat.h" }
diff --git a/libcxx/include/string b/libcxx/include/string
@@ -600,7 +600,6 @@ basic_string<char32_t> operator""s( const char32_t *str, size_t len );
 #  include <__debug_utils/sanitizers.h>
 #  include <__format/enable_insertable.h>
 #  include <__functional/hash.h>
-#  include <__functional/is_transparent.h>
 #  include <__functional/unary_function.h>
 #  include <__fwd/string.h>
 #  include <__iterator/bounded_iter.h>
@@ -629,7 +628,6 @@ basic_string<char32_t> operator""s( const char32_t *str, size_t len );
 #  include <__type_traits/is_allocator.h>
 #  include <__type_traits/is_array.h>
 #  include <__type_traits/is_convertible.h>
-#  include <__type_traits/is_generic_transparent_comparator.h>
 #  include <__type_traits/is_nothrow_assignable.h>
 #  include <__type_traits/is_nothrow_constructible.h>
 #  include <__type_traits/is_replaceable.h>
@@ -2569,20 +2567,6 @@ struct __default_three_way_comparator<basic_string<_CharT, _Traits, _Alloc>, bas
 };
 #  endif
 
-template <class _Comparator, class _CharT, class _Traits, class _Alloc>
-inline const bool __is_transparently_comparable_v<_Comparator,
-                                                  basic_string<_CharT, _Traits, _Alloc>,
-                                                  const _CharT*,
-                                                  __enable_if_t<__is_generic_transparent_comparator_v<_Comparator> > > =
-    true;
-
-template <class _Comparator, class _CharT, class _Traits, class _Alloc, size_t _Np>
-inline const bool __is_transparently_comparable_v<_Comparator,
-                                                  basic_string<_CharT, _Traits, _Alloc>,
-                                                  _CharT[_Np],
-                                                  __enable_if_t<__is_generic_transparent_comparator_v<_Comparator> > > =
-    true;
-
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
           class _CharT     = __iter_value_type<_InputIterator>,
diff --git a/libcxx/test/benchmarks/containers/associative/map.bench.cpp b/libcxx/test/benchmarks/containers/associative/map.bench.cpp
@@ -16,19 +16,6 @@
 #include "../../GenerateInput.h"
 #include "benchmark/benchmark.h"
 
-static void BM_map_find_string_literal(benchmark::State& state) {
-  std::map<std::string, int> map;
-  map.emplace("Something very very long to show a long string situation", 1);
-  map.emplace("Something Else", 2);
-
-  for (auto _ : state) {
-    benchmark::DoNotOptimize(map);
-    benchmark::DoNotOptimize(map.find("Something very very long to show a long string situation"));
-  }
-}
-
-BENCHMARK(BM_map_find_string_literal);
-
 template <class K, class V>
 struct support::adapt_operations<std::map<K, V>> {
   using ValueType = typename std::map<K, V>::value_type;
diff --git a/libcxx/test/benchmarks/containers/associative/unordered_map.bench.cpp b/libcxx/test/benchmarks/containers/associative/unordered_map.bench.cpp
