[libcxx-commits] [libcxx] [libc++] Avoid constructing additional objects when using map::at (PR #157866)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne requested changes to this pull request.

Let's also add a benchmark with e.g. `map.at(string literal)`

https://github.com/llvm/llvm-project/pull/157866