In Xcode 7, we added the ability to include bitcode with your app submission. Including bitcode will allow Apple to re-optimize your app binary in the future without the need to submit a new version of your app to the store. Read App Thinning to learn more.
If you would like to view crashes that originated from your app distributed via TestFlight or App Store, you may use the Xcode Crashes Organizer.
Alternatively, you may retrieve and symbolicate crashes from a distributed app directly from your device using the Devices Window. Xcode will symbolicate the crashes found on your device automatically as long as you have the appropriate dSYMs and the app version that crashed. If you upload your app with bitcode, the App Store will compile your app from bitcode and retain the dSYMs necessary to symbolicate your application’s crashes. The dSYMs can be downloaded at any time using the Archive organizer’s Download dSYMs button. This button downloads the dSYMs from all bitcode compiled generations of your app and inserts them into the the original Archive used to upload your app. In order to download these dSYMs, you must retain the original archive used to upload the app.
For more information on symbolicating distributed apps directly from your device in the Devices window, read Analyzing Crash Reports.