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Also Bitcode[1] which was introduced 5 years ago for iOS, watchOS and tvOS. I have a feeling they'll be making app binaries built with `-fembed-bitcode` optiona

Also Bitcode[1] which was introduced 5 years ago for iOS, watchOS and tvOS. I have a feeling they'll be making app binaries built with `-fembed-bitcode` optional on the Mac App Store and eventually mandatory. [1]: https://help.apple.com/xcode/mac/current/#/devbbdc5ce4f https://help.apple.com/xcode/mac/current/#/devbbdc5ce4f

scarface74 6y ago
The idea that bitcode will allow porting from x86 to ARM was dispelled by non other than Chris Lattner himself during an interview on ATP. https://atp.fm/205-chris-lattner-interview-transcript#bitcode https://atp.fm/205-chris-lattner-interview-transcript#bitcod... John Siracusa: The same thing I would assume for architecture changes, especially if there was an endian difference, because endianness is visible from the C world, so you can’t target different endianness? Chris Lattner: Yep. It’s not something that magically solves all portability problems, but it is very useful for specific problems that Apple’s faced in the past.
- wolfgke 6y ago
  What has endianness to do with porting from x86 to ARM? Typical ARM implementations/ABIs use little endian mode.
  - scarface74 6y ago
    The context of the answer was: John asked: And the more prosaic version: it doesn’t mean it’s CPU-agnostic, all it means is that Apple has slightly more freedom to change instructions on the CPUs that they do target? [10:30] What advantages are there of compiling something to Bitcode and then uploading it somewhere versus sending someone a binary?
- woadwarrior01 6y ago
  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.
  - scarface74 6y ago
    Read the transcript around the quote. It’s not just the endian differences. He said that it basically only helps with things like minor optimizations and added instructions.

scarface74 6y ago

The idea that bitcode will allow porting from x86 to ARM was dispelled by non other than Chris Lattner himself during an interview on ATP. https://atp.fm/205-chris-lattner-interview-transcript#bitcode https://atp.fm/205-chris-lattner-interview-transcript#bitcod... John Siracusa: The same thing I would assume for architecture changes, especially if there was an endian difference, because endianness is visible from the C world, so you can’t target different endianness? Chris Lattner: Yep. It’s not something that magically solves all portability problems, but it is very useful for specific problems that Apple’s faced in the past.

wolfgke 6y ago
What has endianness to do with porting from x86 to ARM? Typical ARM implementations/ABIs use little endian mode.
- scarface74 6y ago
  The context of the answer was: John asked: And the more prosaic version: it doesn’t mean it’s CPU-agnostic, all it means is that Apple has slightly more freedom to change instructions on the CPUs that they do target? [10:30] What advantages are there of compiling something to Bitcode and then uploading it somewhere versus sending someone a binary?
woadwarrior01 6y ago
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.
- scarface74 6y ago
  Read the transcript around the quote. It’s not just the endian differences. He said that it basically only helps with things like minor optimizations and added instructions.