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Lattner refuted the ability of Apple to recompile bitcode into alternate architectures in his recent ATP interview

• Reason077 10y ago
  Lattner said that bitcode is "not a panacea that makes everything magically portable"[1], which of course is true. But that doesn't mean it couldn't be recompiled for different architectures, given reasonable bounds like both 64-bit, same endian, similar calling conventions, etc. I'm not suggesting Apple is considering that, just that it would be technically possible if there were ever a compelling reason. It's unlikely they would ever move away from ARM on iOS, but on something like the Apple Watch with it's highly custom SIP, and ultra-low-power requirements, you never know... [1] http://atp.fm/205-chris-lattner-interview-transcript/#bitcode http://atp.fm/205-chris-lattner-interview-transcript/#bitcod...
  • nstj 10y ago
    He actually references that pretty specifically saying that indeed it can't be used to move 32bit -> 64bit [0] > 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 [0]: http://atp.fm/205-chris-lattner-interview-transcript/#portability http://atp.fm/205-chris-lattner-interview-transcript/#portab...
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