We faced the challenge of seamlessly running 32b application binaries on a new 64b S4 chip, which has no hardware support to run 32b binaries. Translating the ARM binaries directly to the new hardware would be hard, but when an application is available in bitcode format, the task is much more feasible. This talk opens the curtain for an inside look into the decisions and steps taken to translate 32b bitcode for the new 64b hardware. It will discuss the many design, implementation and verification challenges of introducing a new ABI, arm64_32, which guarantees that the binaries for the new S4 chip are compatible to the original 32b applications.
