[llvm] InferAddressSpaces: Handle llvm.fake.use (PR #109567)

[Stephen Tozer via llvm-commits]

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

I don't think there's a problem with landing this as-is; for full context, the current state of llvm.fake.use is that there is no verifier check to enforce having exactly one operand, but the documentation states that it is an error for it to have more than one operand, and SelectionDAG currently assumes a single operand only.
To my knowledge there's not a principled reason for this to be the case, it just simplified the implementation (particularly around ISel), so I'm fine to make the change for variadic fake uses to be properly supported in a future patch, or else if it turns out to cause problems then the verifier check can be added and the tests that depend on it being variadic can be adjusted or removed.

https://github.com/llvm/llvm-project/pull/109567