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

[Sami Tolvanen via cfe-commits]

samitolvanen wrote:

> Actually, I think this code was introduced to address a compatibility issue with KASAN, which apparently must generate KCFI-enabled code without clang. I found this explanation at [3b14862](https://github.com/llvm/llvm-project/commit/3b14862f0a968dc079530acbce4f2ca4aa7c1492) and [ClangBuiltLinux/linux#1742](https://github.com/ClangBuiltLinux/linux/issues/1742).

Yes, this is needed for LLVM generated functions in general. KASAN is one use case, GCOV is another.


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