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

[Scott Constable via cfe-commits]

scottconstable 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?

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