[clang] [X86] Enhance kCFI type IDs with a 3-bit arity indicator. (PR #117121)

[Phoebe Wang via cfe-commits]

phoebewang wrote:

> @phoebewang and @lvwr I also noticed that there is this code in LLVM:
> 
> https://github.com/llvm/llvm-project/blob/9ba6672b9f0e82a1f6d4100dc832c84447ea545c/llvm/lib/Transforms/Utils/ModuleUtils.cpp#L202-L214
> 
> . As far as I can tell, this code is not triggered when I build the Linux kernel with `-fsanitize=kcfi`.
> When is this code triggered? And do you think it is necessary to additionally implement the arity-enhancement to this code?

I'm not familar with KCFI. I find it's added by @samitolvanen in https://github.com/llvm/llvm-project/commit/e1c36bde0551977d4b2efae032af6dfc4b2b3936. I think you should triger it with attached test case.

https://github.com/llvm/llvm-project/pull/117121