[llvm] [SCEV] Add SCEVs for scopes as users of origin SCEV. (PR #119897)

[Florian Hahn via llvm-commits]

fhahn wrote:

> Based on your description, I feel like this is something that forgetLcssaPhiWithNewPredecessor() on modified LCSSA phi nodes should be handling -- why doesn't it? Is there a call missing somewhere or does it not do what is necessary here?


IIUC the issue here is that we need to invalidate `loop.2`'s BTC, which contains `%add.1`'s SCEV at scope of `%loop.2` which is `-100 + (-1 * %l). But I don't think this SCEV is reachable via a chain of IR instructions reachable from the phi node or a SCEV defined inside `loop.1`, so won't be covered by the existing forgetLcssaPhiWithNewPredecessor calls in LV, unless I am missing some existing link?

https://github.com/llvm/llvm-project/pull/119897