将我的应用程序从Xcode 5.1迁移到Xcode 6.0时的屏幕布局问题

My app runs perfectly in Xcode 5.1 in all the simulators.I tried running exactly the same app with no changes at all in Xcode 6.0 and my layout looks totally messed up in all the simulators. I use separate .xib files and the content is populated in code. Even trying to do simple stuff like centering a label on the screen likeMy app runs perfectly in Xcode 5.1 in all the s