[llvm] [Transforms/Util] Add SimplifySwitchVar pass (PR #149937)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

At a high level, I don't think that this is the correct approach to the problem. We should be sinking those GEPs such that there is one GEP with a phi operand, and then existing switch simplification will take care of the rest.

https://github.com/llvm/llvm-project/pull/149937