[llvm] [LoopVersioning] Add a check to see if the input loop is in LCSSA form (PR #116443)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks commented:

I'm familiar with the pass and will let @fhahn take a look, but does it need to be a function pass as opposed to a loop pass?

https://github.com/llvm/llvm-project/pull/116443