[libcxx-commits] [libcxx] Optimize __assign_with_sentinel in std::vector (PR #113852)

[Louis Dionne via libcxx-commits]

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@@ -1031,9 +1031,14 @@ template <class _Tp, class _Allocator>
 template <class _Iterator, class _Sentinel>
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ldionne wrote:

http://eel.is/c++draft/container.requirements#sequence.reqmts-57 says:

> T is Cpp17EmplaceConstructible into X from *i and assignable from *i[.](http://eel.is/c++draft/container.requirements#sequence.reqmts-57.sentence-1) For vector, if the iterator does not meet the forward iterator requirements ([[forward.iterators]](http://eel.is/c++draft/forward.iterators)), T is also Cpp17MoveInsertable into X[.](http://eel.is/c++draft/container.requirements#sequence.reqmts-57.sentence-2) Neither i nor j are iterators into a[.](http://eel.is/c++draft/container.requirements#sequence.reqmts-57.sentence-3)

Since we do have a requirement that T is assignable from `*i`, I think we're allowed to do this.

Can you check if we already have a benchmark that would cover this inside our vector benchmarks, and if not, add one?

https://github.com/llvm/llvm-project/pull/113852