How to set auto-scaling on an app (optimized for iPhone 6's 4.7 inch screen) to fit iPhone 5 and 4's screen?

I have seen old iOS apps auto-scale to fit iPhone 6/6+'s large screen on iOS 8. I have recently developed an app which is optimized to display on iPhone 6's 4.7 inch screen. Apply auto-layouts would be lots of work because a lot of views are created programmatically so I am wondering is it possible to make an app auto-scale to fit smaller screens?