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Lots of suspicion because of the move to force App Store apps to have Bitcode enabled for submission. This would allow them to potentially transpile x86 apps fo

Lots of suspicion because of the move to force App Store apps to have Bitcode enabled for submission. This would allow them to potentially transpile x86 apps for ARM: https://lowlevelbits.org/bitcode-demystified/ https://lowlevelbits.org/bitcode-demystified/ Also as we've seen with iPad Pro + AWS M6G instances the performance is now there to power desktops.

scarface74 7y ago
This is not true. It would not allow them to transpile between architectures. This myth was dispelled by no less than Chris Lattner on ATP. Even though he did later admit that he wasn’t completely being honest. Part of the purpose of the bitcode requirement for the Watch was that Apple knew that they would be shipping a 64 bit chip for the Watch two years later. https://atp.fm/205-chris-lattner-interview-transcript https://atp.fm/205-chris-lattner-interview-transcript Bitcode is not [12:30] a magic solution, though. You can't take a 32-bit app, for example, and run it on a 64-bit device. That kind of portability isn’t something that Bitcode can give you, notably because that is something that's visible in C. As you're writing C code, you can write #ifdef pointer size equals 32, and that’s something that Bitcode can't abstract over. It's useful for very specific, low-level kinds of enhancements, but it isn't a panacea that makes everything [13:00] magically portable. 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.
- Rolcol 7y ago
  In the case of a Mac transition, applications would go from little-endian 64bit x86_64 to little-endian 64bit AArch64.
- threeseed 7y ago
  All of the OSX apps are 64-bit. And ARM I believe has runtime-selectable endianness.
  - scarface74 7y ago
    He wasn’t saying that the only difficulty in using bitcode was translating from 32 bit to 64 bit and endianness but just thst was one of the issues.
kristianp 7y ago
On one hand, an ARM powered mac would increase Apple's profitability by not having to pay Intel for processors, on the other hand there's a. the disruption and confusion an architecture switch would cause, and b. Apple's lack of interest in the laptop platform relative to Ipad pro and mobile. Someone demoed transpiling bitcode to x86_64, it seems going the other direction wouldn't be a big problem, it's stock clang: https://www.highcaffeinecontent.com/blog/20190518-Translating-an-ARM-iOS-App-to-Intel-macOS-Using-Bitcode https://www.highcaffeinecontent.com/blog/20190518-Translatin...
- leokennis 7y ago
  Won’t switching form Intel to ARM allow Apple to basically double battery life for the same performance (or double performance with equal battery life)? If I’d had a laptop like that on offer, my interest in the laptop platform would be surely rekindled as half the earth would line up around the block to buy one...
- RossBencina 7y ago
  I don't see it causing any more disruption and confusion than the switch from 68k to PPC, from PPC to x86, or discontinuing support for 10+ years worth of 32-bit executables.
  - macintux 7y ago
    It used to be the case that emulating Intel on ARM would be much slower than the emulators that supported previous transitions. Given how impressive the recent Apple chips are, perhaps that's less of an issue now.

scarface74 7y ago

This is not true. It would not allow them to transpile between architectures. This myth was dispelled by no less than Chris Lattner on ATP. Even though he did later admit that he wasn’t completely being honest. Part of the purpose of the bitcode requirement for the Watch was that Apple knew that they would be shipping a 64 bit chip for the Watch two years later. https://atp.fm/205-chris-lattner-interview-transcript https://atp.fm/205-chris-lattner-interview-transcript Bitcode is not [12:30] a magic solution, though. You can't take a 32-bit app, for example, and run it on a 64-bit device. That kind of portability isn’t something that Bitcode can give you, notably because that is something that's visible in C. As you're writing C code, you can write #ifdef pointer size equals 32, and that’s something that Bitcode can't abstract over. It's useful for very specific, low-level kinds of enhancements, but it isn't a panacea that makes everything [13:00] magically portable. 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.

Rolcol 7y ago
In the case of a Mac transition, applications would go from little-endian 64bit x86_64 to little-endian 64bit AArch64.
threeseed 7y ago
All of the OSX apps are 64-bit. And ARM I believe has runtime-selectable endianness.
- scarface74 7y ago
  He wasn’t saying that the only difficulty in using bitcode was translating from 32 bit to 64 bit and endianness but just thst was one of the issues.

kristianp 7y ago

On one hand, an ARM powered mac would increase Apple's profitability by not having to pay Intel for processors, on the other hand there's a. the disruption and confusion an architecture switch would cause, and b. Apple's lack of interest in the laptop platform relative to Ipad pro and mobile. Someone demoed transpiling bitcode to x86_64, it seems going the other direction wouldn't be a big problem, it's stock clang: https://www.highcaffeinecontent.com/blog/20190518-Translating-an-ARM-iOS-App-to-Intel-macOS-Using-Bitcode https://www.highcaffeinecontent.com/blog/20190518-Translatin...

leokennis 7y ago
Won’t switching form Intel to ARM allow Apple to basically double battery life for the same performance (or double performance with equal battery life)? If I’d had a laptop like that on offer, my interest in the laptop platform would be surely rekindled as half the earth would line up around the block to buy one...
RossBencina 7y ago
I don't see it causing any more disruption and confusion than the switch from 68k to PPC, from PPC to x86, or discontinuing support for 10+ years worth of 32-bit executables.
- macintux 7y ago
  It used to be the case that emulating Intel on ARM would be much slower than the emulators that supported previous transitions. Given how impressive the recent Apple chips are, perhaps that's less of an issue now.