[llvm] [MachinePipeliner] Fix loop-carried dependencies analysis (PR #121907)

[Ryotaro Kasuga via llvm-commits]

kasuga-fj wrote:

Thank you for sharing. Let me ask a question. Is this the only case that causes regression? Or are there other cases? This patch addresses correctness issues, and I believe that is generally more important than performance. However, if there are many performance regressions, I think it would be one way to create an option to enable/disable the changes of this patch. Does such a flag make sense for the Hexagon backend?

https://github.com/llvm/llvm-project/pull/121907