[libcxx-commits] [libcxx] Optimize std::__tree::__assign_multi to insert the provided range at the end of the tree every time (PR #131030)

[via libcxx-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: None (higher-performance)

<details>
<summary>Changes</summary>

This improves performance for the copy-assignment operators of associative containers such as `std::map`.

Note that this optimization already exists in other places, e.g.:

https://github.com/llvm/llvm-project/blob/15e6bb6224177805d8b6a8268f08a2b88ae4dd70/libcxx/include/map#L1217-L1218

---
Full diff: https://github.com/llvm/llvm-project/pull/131030.diff


1 Files Affected:

- (modified) libcxx/include/__tree (+2-1) 


``````````diff
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
index c627641d5d86f..c07de5c95b0dc 100644
--- a/libcxx/include/__tree
+++ b/libcxx/include/__tree
@@ -1432,8 +1432,9 @@ 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>

``````````

</details>


https://github.com/llvm/llvm-project/pull/131030