[libcxx-commits] [libcxx] [libc++] Optimize {set, map}::{lower, upper}_bound (PR #161366)

[Louis Dionne via libcxx-commits]

================
@@ -1165,32 +1165,81 @@ public:
   template <class _Key>
   _LIBCPP_HIDE_FROM_ABI size_type __count_multi(const _Key& __k) const;
 
+  template <bool _LowerBound, class _Key>
+  _LIBCPP_HIDE_FROM_ABI __end_node_pointer __lower_upper_bound_unique_impl(const _Key& __v) const {
+    auto __rt     = __root();
+    auto __result = __end_node();
+    auto __comp   = __lazy_synth_three_way_comparator<_Compare, _Key, value_type>(value_comp());
+    while (__rt != nullptr) {
+      auto __comp_res = __comp(__v, __rt->__get_value());
+
+      if (__comp_res.__less()) {
+        __result = static_cast<__end_node_pointer>(__rt);
+        __rt     = static_cast<__node_pointer>(__rt->__left_);
+      } else if (__comp_res.__greater()) {
+        __rt = static_cast<__node_pointer>(__rt->__right_);
+      } else if _LIBCPP_CONSTEXPR (_LowerBound) {
+        return static_cast<__end_node_pointer>(__rt);
+      } else {
+        return __rt->__right_ ? static_cast<__end_node_pointer>(std::__tree_min(__rt->__right_)) : __result;
+      }
+    }
+    return __result;
+  }
+
   template <class _Key>
-  _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const _Key& __v) {
-    return __lower_bound(__v, __root(), __end_node());
+  _LIBCPP_HIDE_FROM_ABI iterator __lower_bound_unique(const _Key& __v) {
+    return iterator(__lower_upper_bound_unique_impl<true>(__v));
   }
+
   template <class _Key>
-  _LIBCPP_HIDE_FROM_ABI iterator __lower_bound(const _Key& __v, __node_pointer __root, __end_node_pointer __result);
+  _LIBCPP_HIDE_FROM_ABI const_iterator __lower_bound_unique(const _Key& __v) const {
+    return const_iterator(__lower_upper_bound_unique_impl<true>(__v));
+  }
+
   template <class _Key>
-  _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const _Key& __v) const {
-    return __lower_bound(__v, __root(), __end_node());
+  _LIBCPP_HIDE_FROM_ABI iterator __upper_bound_unique(const _Key& __v) {
+    return iterator(__lower_upper_bound_unique_impl<false>(__v));
+  }
+
+  template <class _Key>
+  _LIBCPP_HIDE_FROM_ABI const_iterator __upper_bound_unique(const _Key& __v) const {
+    return iterator(__lower_upper_bound_unique_impl<false>(__v));
   }
+
+  template <class _Key>
+  _LIBCPP_HIDE_FROM_ABI iterator __lower_bound(const _Key& __v, __node_pointer __root, __end_node_pointer __result);
+
   template <class _Key>
   _LIBCPP_HIDE_FROM_ABI const_iterator
   __lower_bound(const _Key& __v, __node_pointer __root, __end_node_pointer __result) const;
+
   template <class _Key>
-  _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const _Key& __v) {
-    return __upper_bound(__v, __root(), __end_node());
+  _LIBCPP_HIDE_FROM_ABI iterator __lower_bound_multi(const _Key& __v) {
+    return __lower_bound(__v, __root(), __end_node());
   }
   template <class _Key>
-  _LIBCPP_HIDE_FROM_ABI iterator __upper_bound(const _Key& __v, __node_pointer __root, __end_node_pointer __result);
+  _LIBCPP_HIDE_FROM_ABI const_iterator __lower_bound_multi(const _Key& __v) const {
+    return __lower_bound(__v, __root(), __end_node());
+  }
+
   template <class _Key>
-  _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const _Key& __v) const {
+  _LIBCPP_HIDE_FROM_ABI iterator __upper_bound_multi(const _Key& __v) {
     return __upper_bound(__v, __root(), __end_node());
   }
+
+  template <class _Key>
+  _LIBCPP_HIDE_FROM_ABI const_iterator __upper_bound_multi(const _Key& __v) const {
+    return __upper_bound(__v, __root(), __end_node());
+  }
+
+  template <class _Key>
+  _LIBCPP_HIDE_FROM_ABI iterator __upper_bound(const _Key& __v, __node_pointer __root, __end_node_pointer __result);
----------------
ldionne wrote:

I would rename this to `__upper_bound_multi` yet keep the `__root` and `__result` parameters. IMO that makes it clearer.

Also, can this be made `private`? Same comments for `__lower_bound`.

https://github.com/llvm/llvm-project/pull/161366