Optimize std::__tree::__assign_multi to insert the provided range at the end of the tree every time (#131030)

higher-performance · web-flow · commit 5f9164978b21 · 2025-04-24T14:30:28.000-04:00
This improves performance for the copy-assignment operators of associative containers such as `std::map`.

This optimization already exists in other places in the codebase, and seems to have been missed here.
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
@@ -1411,8 +1411,9 @@ void __tree<_Tp, _Compare, _Allocator>::__assign_multi(_InputIterator __first, _
       __cache.__advance();
     }
   }
+  const_iterator __e = end();
   for (; __first != __last; ++__first)
-    __insert_multi(_NodeTypes::__get_value(*__first));
+    __insert_multi(__e, _NodeTypes::__get_value(*__first));
 }
 
 template <class _Tp, class _Compare, class _Allocator>

Original file line number	Diff line number	Diff line change
`@@ -1411,8 +1411,9 @@ void __tree<_Tp, _Compare, _Allocator>::__assign_multi(_InputIterator __first, _`
`1411`	`1411`	`__cache.__advance();`
`1412`	`1412`	`}`
`1413`	`1413`	`}`
	`1414`	`+ const_iterator __e = end();`
`1414`	`1415`	`for (; __first != __last; ++__first)`
`1415`		`- __insert_multi(_NodeTypes::__get_value(*__first));`
	`1416`	`+ __insert_multi(__e, _NodeTypes::__get_value(*__first));`
`1416`	`1417`	`}`
`1417`	`1418`
`1418`	`1419`	`template <class _Tp, class _Compare, class _Allocator>`