[llvm] [DA] Add initial support for monotonicity check (PR #162280)

[Ehsan Amiri via llvm-commits]

amehsan wrote:

>  only when the offset is an affine addrec

Yes, it is probably provably correct for affine addrec and affine addrec should cover most practically interesting cases. We'll look into implementing this logic earlier in the pipeline so it can help DA and potentially other passes too. 

https://github.com/llvm/llvm-project/pull/162280