[clang] [llvm] [X86] Extend kCFI with a 3-bit arity indicator (PR #121070)

[Matthew Maurer via llvm-commits]

maurer wrote:

> > If hashing is changed, consider replacing xxhash64 with xxh3+_64bits
> 
> @MaskRay This PR does not change the hashing scheme at all.

I think their point is that even if you are not changing the hash scheme, you are proposing breaking compatibility of the identifier with existing code. Since we don't want to do this many times, if we are breaking compatibility with existing code, they would like to batch it with another breaking update so that it doesn't need to be done again.

(This isn't me reviewing this PR, just trying to clear up some confusion.)

https://github.com/llvm/llvm-project/pull/121070