You seem to be assuming that the CPU on iOS devices are running in big-endian mode. ARM CPUs support both big endian and little endian modes and ARMs on Apple i

You seem to be assuming that the CPU on iOS devices are running in big-endian mode. ARM CPUs support both big endian and little endian modes and ARMs on Apple i-devices have been running on little endian mode for as long as they've been around. There is no endian difference gap to bridge between ARMs on iPhones and x86 CPUs. Given this, it's quite unlikely that Apple will go big endian in their Desktop/Laptop ARM CPUs. Of course, Bitcode won't solve all portability problems, but it does solve many of them in this specific case.