[llvm] [LoopFusion] Validate loop structure before creating LoopCandidates (PR #192280)

[Congzhe Cao via llvm-commits]

CongzheUalberta wrote:

I think you should call `isLoopSimplifyForm()` to check if the loop is in simplified state. The pass already does it but you probably need to move that piece of code to before or at the beginning of construction of `FusionCandidate`.

https://github.com/llvm/llvm-project/pull/192280