[llvm] Do not treat llvm.fake.use as a debug instruction (PR #128684)

[Orlando Cazalet-Hyams via llvm-commits]

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

Thanks for the inline explanation, no further concerns from me so LGTM

I suppose this might have knock on effects besides in SimplifyCFG, but as you have outlined if the previous behaviour is discovered to have been desirable it should be special-cased at those sites.

https://github.com/llvm/llvm-project/pull/128684