[llvm] [MC] Use a variant to hold MCCFIInstruction state (NFC) (PR #164720)

[Orlando Cazalet-Hyams via llvm-commits]

https://github.com/OCHyams approved this pull request.

I'm not sure who is best to review the patches in this stack, possibly @MaskRay?

Am I right in thinking this patch reduces the size of the class due to making the `Comment` and `Values` field disjoint?

I don't often have a reason to visit MC code, but this one looks fairly straightforward.

https://github.com/llvm/llvm-project/pull/164720