[llvm] [LoopPeel] LCSSA form is destroyed by LoopPeel, preserve it (PR #78696)

[Vedant Paranjape via llvm-commits]

vedantparanjape-amd wrote:

> @vedantparanjape-amd , going by the definition of LCSSA, I see that %0 is not used anywhere outside of the loop headed by bb1 except by the phi node in bb7, which I believe is permitted(going by this example in llvm-docs [Link](https://llvm.org/docs/LoopTerminology.html#loop-closed-ssa-lcssa)). Therefore in my opinion the code at the end of LoopPeel is already in LCSSA.

I think the issue comes up due to the presence of the inner loop inside this loop.

https://github.com/llvm/llvm-project/pull/78696