Redux: Calling store.getState() in a reducer function, is that an anti pattern?

Yes, this is absolutely an anti-pattern. Reducer functions should be "pure", and only based on their direct inputs (the current state and the action).

The Redux FAQ discusses this kind of issue, in the FAQ on sharing state between reducers. Basically, you should either write some custom reducer logic that passes down the additional information needed, or put more information into your action.

I also wrote a section for the Redux docs called Structuring Reducers, which discusses a number of important concepts related to reducer logic. I'd encourage you to read through that.