[llvm] [LICM][MustExec] Make must-exec logic for IV condition commutative (PR #93150)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

> I don't think we would be able to directly report umax(N, N+1) as the exit count

We can use umax(N, N+1) as the count as long as the AddRec is nowrap, I think?  And if the AddRec isn't nowrap, we can add that as a predicate.  That's basically the same reasoning we're using to return zext(N)+1 anyway.

https://github.com/llvm/llvm-project/pull/93150