SPOILERS For Flash Season 3 Episode 21
Ok so Savitar told Barry in this episode that he is a Future Time remenant and that he was created to help Real-Barry save Iris. This means that until Barry creates Savitar, Savitar will have all of the memories of Barry's plans to stop him. If Barry wants to save Iris he needs to create Savitar and then create a new plan to stop him. It sucks for Barry because he is going to have to create his worst enemy to save Iris.
Predictions for the final episode:
Barry won't create any time remenants and he will watch Iris die.
He will then create the time remenants and travel back in time to save Iris and create Savitar.