5 ms·

A shame operating systems like iOS/iPadOS do not allow JIT. iPad Pro's have such fast CPU's that you cant even use fully because of decisions like this.

Pulcinella 1y ago
Those operating systems allow it, but Apple does not. Agree that it is a total waste.
duped 1y ago
What advantage does JIT compilation have over Swift or Obj-C?
- saagarjha 1y ago
  It speeds up interpreted languages.
  - Pulcinella 1y ago
    And emulation.
    - saagarjha 1y ago
      What is an architecture but a scripting language to interpret? ;)
  - duped 1y ago
    I get that, but what interpreted language do you want to write iOS apps in when there's Swift and Obj-C right there, with bespoke support and tooling from Apple? And if you care about performance, why aren't you writing that code in native to begin with?
    - saagarjha 1y ago
      Why would you care about faster cars when planes exist?
      - ranger_danger 1y ago
        https://0x0.st/XJZT.jpg https://0x0.st/XJZT.jpg
    - ranger_danger 1y ago
      ...Javascript.
- bencyoung 1y ago
  JIT compilation can be faster for compiled languages too, as it allows data driven inlining and devirtualization, as well as "effective constant" propogation and runtime architecture feature detection
  - varjag 1y ago
    It can be but it never is.
    - __s 1y ago
      Especially after PGO (profiling guided optimization) gets most of the way there
    - ignoramous 1y ago
      To re-optimize compiled code blocks isn't without effort. Google has publicly spoken about AutoFDO and Propeller [0], after Meta had open sourced BOLT [1] in 2021. AutoFDO has since been ported to Android and adopted by Yandex [3]. [0] https://lwn.net/Articles/995397/ https://lwn.net/Articles/995397/ [1] https://news.ycombinator.com/item?id=40868224 https://news.ycombinator.com/item?id=40868224 [2] https://news.ycombinator.com/item?id=42896716 https://news.ycombinator.com/item?id=42896716
    - Rohansi 1y ago
      But is that because of JIT compilation or other decisions for how the language should work (dynamic typing, GC, etc.)?
    - ranger_danger 1y ago
      Hard disagree. Many newer game system emulators (32-bit and up) rely on JIT or "dynarecs" to get playable speeds, and they pretty much all use high performance compiled languages already. They often double the performance over their interpreter or more.
  - duped 1y ago
    Is there a production JIT for a compiled language that is actually faster? I understand the theory, I don't think the practice backs it up.
almostgotcaught 1y ago
> that you cant even use fully because of decisions like this. Have no clue what this means - you can pre-compile for target platforms and therefore "fully" use whichever Apple device CPU.
- deleted 1y ago
  [deleted]
- pjc50 1y ago
  You can't precompile your web page's Javascript for iOS, even if you're willing to have it signed and notarized and submitted for policy review.
  - tgv 1y ago
    Apart from the fact that its JS engine is really fast, Safari accepts WebAssembly. What else would you precompile it to?
    - true_religion 1y ago
      Originally, iOS Safari handled WASM but only with JIT disabled. However the EU decreed that it must allow for fair competition, leading to it claiming that it will enable JIT for authorized developers: https://developer.apple.com/support/alternative-browser-engines/ https://developer.apple.com/support/alternative-browser-engi... But I'm not sure that they have done so... Mozilla: https://github.com/mozilla/platform-tilt/issues/3 https://github.com/mozilla/platform-tilt/issues/3 Chrome: https://issues.chromium.org/issues/42203058 https://issues.chromium.org/issues/42203058
pjscott 1y ago
They do, technically, allow JIT. You need a very hard-to-obtain entitlement that lets you turn writable pages into executable read-only pages, and good luck getting that entitlement if (for some reason) your name isn’t “mobilesafari”, but the capability exists.
- Wowfunhappy 1y ago
  When you say it's "hard" to obtain--is it possible to obtain if you aren't Apple? Does Apple ever provide it to third party developers, or is there even a path to requesting it?
  - j16sdiz 1y ago
    Yes.
    - cmeacham98 1y ago
      Source? Is there any non-Apple app that has this entitlement?
      - Rohansi 1y ago
        If your app happens to be a browser that's only usable in the EU then: https://developer.apple.com/documentation/browserenginekit/protecting-code-compiled-just-in-time https://developer.apple.com/documentation/browserenginekit/p...
      - gf000 1y ago
        I believe the Delta emulator has JIT support, but possibly only when installed as a developer.
        Wowfunhappy 1y ago
        As far as I can tell, you need to connect your phone to a PC running software which enables JIT by exploiting a feature intended for remote debugging. https://faq.altstore.io/altstore-classic/enabling-jit https://faq.altstore.io/altstore-classic/enabling-jit
ivankra 1y ago
They allow, but Apple's policy is to lock down that ability pretty much just to Safari/WKWebView. If you could transpile/compile your program to JS or WASM and run it through one of these blessed options, it should get JIT'ted.
xxs 1y ago
Of course they do - this is how javascript in any site works

Pulcinella 1y ago

Those operating systems allow it, but Apple does not. Agree that it is a total waste.

duped 1y ago

What advantage does JIT compilation have over Swift or Obj-C?

saagarjha 1y ago
It speeds up interpreted languages.
- Pulcinella 1y ago
  And emulation.
  - saagarjha 1y ago
    What is an architecture but a scripting language to interpret? ;)
- duped 1y ago
  I get that, but what interpreted language do you want to write iOS apps in when there's Swift and Obj-C right there, with bespoke support and tooling from Apple? And if you care about performance, why aren't you writing that code in native to begin with?
  - saagarjha 1y ago
    Why would you care about faster cars when planes exist?
    - ranger_danger 1y ago
      https://0x0.st/XJZT.jpg https://0x0.st/XJZT.jpg
  - ranger_danger 1y ago
    ...Javascript.
bencyoung 1y ago
JIT compilation can be faster for compiled languages too, as it allows data driven inlining and devirtualization, as well as "effective constant" propogation and runtime architecture feature detection
- varjag 1y ago
  It can be but it never is.
  - __s 1y ago
    Especially after PGO (profiling guided optimization) gets most of the way there
  - ignoramous 1y ago
    To re-optimize compiled code blocks isn't without effort. Google has publicly spoken about AutoFDO and Propeller [0], after Meta had open sourced BOLT [1] in 2021. AutoFDO has since been ported to Android and adopted by Yandex [3]. [0] https://lwn.net/Articles/995397/ https://lwn.net/Articles/995397/ [1] https://news.ycombinator.com/item?id=40868224 https://news.ycombinator.com/item?id=40868224 [2] https://news.ycombinator.com/item?id=42896716 https://news.ycombinator.com/item?id=42896716
  - Rohansi 1y ago
    But is that because of JIT compilation or other decisions for how the language should work (dynamic typing, GC, etc.)?
  - ranger_danger 1y ago
    Hard disagree. Many newer game system emulators (32-bit and up) rely on JIT or "dynarecs" to get playable speeds, and they pretty much all use high performance compiled languages already. They often double the performance over their interpreter or more.
- duped 1y ago
  Is there a production JIT for a compiled language that is actually faster? I understand the theory, I don't think the practice backs it up.

almostgotcaught 1y ago

> that you cant even use fully because of decisions like this. Have no clue what this means - you can pre-compile for target platforms and therefore "fully" use whichever Apple device CPU.

deleted 1y ago
[deleted]
pjc50 1y ago
You can't precompile your web page's Javascript for iOS, even if you're willing to have it signed and notarized and submitted for policy review.
- tgv 1y ago
  Apart from the fact that its JS engine is really fast, Safari accepts WebAssembly. What else would you precompile it to?
  - true_religion 1y ago
    Originally, iOS Safari handled WASM but only with JIT disabled. However the EU decreed that it must allow for fair competition, leading to it claiming that it will enable JIT for authorized developers: https://developer.apple.com/support/alternative-browser-engines/ https://developer.apple.com/support/alternative-browser-engi... But I'm not sure that they have done so... Mozilla: https://github.com/mozilla/platform-tilt/issues/3 https://github.com/mozilla/platform-tilt/issues/3 Chrome: https://issues.chromium.org/issues/42203058 https://issues.chromium.org/issues/42203058

pjscott 1y ago

They do, technically, allow JIT. You need a very hard-to-obtain entitlement that lets you turn writable pages into executable read-only pages, and good luck getting that entitlement if (for some reason) your name isn’t “mobilesafari”, but the capability exists.

Wowfunhappy 1y ago
When you say it's "hard" to obtain--is it possible to obtain if you aren't Apple? Does Apple ever provide it to third party developers, or is there even a path to requesting it?
- j16sdiz 1y ago
  Yes.
  - cmeacham98 1y ago
    Source? Is there any non-Apple app that has this entitlement?
    - Rohansi 1y ago
      If your app happens to be a browser that's only usable in the EU then: https://developer.apple.com/documentation/browserenginekit/protecting-code-compiled-just-in-time https://developer.apple.com/documentation/browserenginekit/p...
    - gf000 1y ago
      I believe the Delta emulator has JIT support, but possibly only when installed as a developer.
      - Wowfunhappy 1y ago
        As far as I can tell, you need to connect your phone to a PC running software which enables JIT by exploiting a feature intended for remote debugging. https://faq.altstore.io/altstore-classic/enabling-jit https://faq.altstore.io/altstore-classic/enabling-jit

ivankra 1y ago

They allow, but Apple's policy is to lock down that ability pretty much just to Safari/WKWebView. If you could transpile/compile your program to JS or WASM and run it through one of these blessed options, it should get JIT'ted.

xxs 1y ago

Of course they do - this is how javascript in any site works