[llvm] [DAGCombiner] Port custom DAG combine for `rem` from NVPTX (PR #210344)

[via llvm-commits]

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def3r wrote:

If I try to add a condition like: `TLI.isOperationLegal(Opcode, VT.getScalarType())` other targets that could have avoided a mod libcall now fall through. How can i avoid that?

https://github.com/llvm/llvm-project/pull/210344