[clang] [Clang] Add `noalias` to `this` pointer in C++ constructors (PR #136792)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

That said, in terms of whether we actually care about what the committee says... both the C and C++ committees have a terrible track record on the fine details of stuff related to memory.  I'd be okay with being slightly more aggressive than the standard technically allows if we can show it's actually helpful in practice.

I'd like to see performance numbers before we go too deep into the weeds, though; we should make sure this actually helps in practice before we go too deep into figuring out the exact semantics/acceptance criteria.

https://github.com/llvm/llvm-project/pull/136792