[llvm] [LoopInterchange] Support inner-loop simple reductions via UndoSimpleReduction (PR #172970)

[Yingying Wang via llvm-commits]

buggfg wrote:

Hi @kasuga-fj , I have made improvements based on your suggestions and added four negative tests. Would you be willing to review this change when you have a chance? Many thanks in advance :)

https://github.com/llvm/llvm-project/pull/172970