[llvm] [LoopInterchange] Relax the legality check to accept more patterns (PR #118267)

[Ryotaro Kasuga via llvm-commits]

kasuga-fj wrote:

I think the easiest way is to check the depth of each of the two loops in the original code. If the depth of `OuterLoopId` is greater than `InnerLoopId`, it means that these loops have already been interchanged. However, it seems that the profitability checks have a "hierarchy". That is, if respecting the current implementation, the decision made by `isProfitablePerLoopCacheAnalysis` should take precedence over that of `isProfitablePerIntsrOrderCost`. So it might not be that simple.
What do you think?

https://github.com/llvm/llvm-project/pull/118267