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

[Scott Constable via llvm-commits]

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@@ -254,6 +254,7 @@ FEATURE(is_trivially_constructible, LangOpts.CPlusPlus)
 FEATURE(is_trivially_copyable, LangOpts.CPlusPlus)
 FEATURE(is_union, LangOpts.CPlusPlus)
 FEATURE(kcfi, LangOpts.Sanitize.has(SanitizerKind::KCFI))
+FEATURE(kcfi_x86_arity, LangOpts.Sanitize.has(SanitizerKind::KCFI))
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scottconstable wrote:

@Darksonn This PR differs from https://github.com/llvm/llvm-project/pull/117121 in that this PR does not change the hash type. Instead, this PR uses the reg field in the `MOVri32` instruction to encode some additional meta data about the function's arity.

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