[llvm] [InstCombine] Simplify nested selects with implied condition (PR #83739)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

This looks basically fine, but I think it may subsume some existing folds?

For example, what about this one? https://github.com/llvm/llvm-project/blob/27ce5121ee875c337dd0f977b00afcb756977f62/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp#L3646-L3651

There's also foldAndOrOfSelectUsingImpliedCond() -- I think your fold may be the same, but without the limitation that the top-level select is a logical one?

https://github.com/llvm/llvm-project/pull/83739