[llvm] Allow folding icmp eq (add X, C2), C when there is more than one-use when we can compute the range (PR #144566)

[via llvm-commits]

AZero13 wrote:

Actually @topperc We can merge this, but the code you modified does not seem obvious in what it is doing with the equality. But I will address this once I do multiple PRs that address the root cause because this cannot be done in one PR.

https://github.com/llvm/llvm-project/pull/144566