[clang] [Clang] Optimize -Wunsafe-buffer-usage. (PR #124554)

[Ilya Biryukov via cfe-commits]

https://github.com/ilya-biryukov commented:

I only have a few suggestions left, overall this LG.


Could you also add a description for the PR that explains the motivation and approach taken for the rewrite?
Benchmark numbers would also be needed there.

Thanks!

https://github.com/llvm/llvm-project/pull/124554