[libcxx-commits] [libcxx] [libc++] Add __is_transparently_comparable_v optimizations for multimap and for some map functions [Issue 187105] (PR #188799)

[via libcxx-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Michael Levine (levinem)

<details>
<summary>Changes</summary>

This PR relates to https://github.com/llvm/llvm-project/issues/187105 but only handles the `std::map` and `std::multimap` portion.

It adds `__is_transparently_comparable_v` checks to:
-  `std::map`'s `count` and `equal_range`
- `std::multimap`'s `find`, `contains`, `lower_bound`, `upper_bound`, `count`, and `equal_range`

Tests in https://github.com/llvm/llvm-project/pull/187345 can be expanded to cover these new optimizations.

Assisted by:  Claude Code


---
Full diff: https://github.com/llvm/llvm-project/pull/188799.diff


1 Files Affected:

- (modified) libcxx/include/map (+39-13) 


``````````diff
diff --git a/libcxx/include/map b/libcxx/include/map
index b7031aeb51c7a..09db3982db526 100644
--- a/libcxx/include/map
+++ b/libcxx/include/map
@@ -1331,7 +1331,9 @@ public:
     return __tree_.__count_unique(__k);
   }
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type count(const _K2& __k) const {
     return __tree_.__count_multi(__k);
   }
@@ -1403,11 +1405,15 @@ public:
     return __tree_.__equal_range_unique(__k);
   }
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const _K2& __k) {
     return __tree_.__equal_range_multi(__k);
   }
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const _K2& __k) const {
     return __tree_.__equal_range_multi(__k);
   }
@@ -1917,11 +1923,15 @@ public:
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator find(const key_type& __k) { return __tree_.find(__k); }
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator find(const key_type& __k) const { return __tree_.find(__k); }
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator find(const _K2& __k) {
     return __tree_.find(__k);
   }
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator find(const _K2& __k) const {
     return __tree_.find(__k);
   }
@@ -1931,7 +1941,9 @@ public:
     return __tree_.__count_multi(__k);
   }
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type count(const _K2& __k) const {
     return __tree_.__count_multi(__k);
   }
@@ -1939,7 +1951,9 @@ public:
 
 #  if _LIBCPP_STD_VER >= 20
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool contains(const key_type& __k) const { return find(__k) != end(); }
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool contains(const _K2& __k) const {
     return find(__k) != end();
   }
@@ -1954,12 +1968,16 @@ public:
   }
 
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const _K2& __k) {
     return __tree_.__lower_bound_multi(__k);
   }
 
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const _K2& __k) const {
     return __tree_.__lower_bound_multi(__k);
   }
@@ -1974,11 +1992,15 @@ public:
   }
 
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const _K2& __k) {
     return __tree_.__upper_bound_multi(__k);
   }
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const _K2& __k) const {
     return __tree_.__upper_bound_multi(__k);
   }
@@ -1991,11 +2013,15 @@ public:
     return __tree_.__equal_range_multi(__k);
   }
 #  if _LIBCPP_STD_VER >= 14
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const _K2& __k) {
     return __tree_.__equal_range_multi(__k);
   }
-  template <typename _K2, class _Comp = _Compare, enable_if_t<__is_transparent_v<_Comp>, int> = 0>
+  template <typename _K2,
+            class _Comp = _Compare,
+            enable_if_t<__is_transparent_v<_Comp> || __is_transparently_comparable_v<_Comp, key_type, _K2>, int> = 0>
   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const _K2& __k) const {
     return __tree_.__equal_range_multi(__k);
   }

``````````

</details>


https://github.com/llvm/llvm-project/pull/188799