[Development] V8 on iOS

[aaron.kennedy at nokia.com]

Hi,

On 02/04/2012, at 3:04 PM, ext marius.storm-olsen at nokia.com wrote:

> On 02/04/2012 08:06, ext Thiago Macieira wrote:
>> On segunda-feira, 2 de abril de 2012 13.02.08,
>> aaron.kennedy at nokia.com wrote:
>>> On 02/04/2012, at 2:21 PM, ext Ian wrote:
>>>> Chris, Thanks for your answer. So, the low-down is that it's not
>>>> (practically) possible to use QML without V8, and even if V8 did
>>>> have a interpreter backend, it would be too slow to be useable?
>>>> If so, I guess I'm going to have to find a way to get V8 working
>>>> on iOS…
>>> 
>>> V8 with an interpreter backend would probably be fine.  However, V8
>>> doesn't have such a backend and writing one would be an enormous
>>> effort - akin to one of their architecture ports.
>> 
>> I estimated a 40k contribution to do that.
>> 
>>> The key to getting V8 running on iOS will be executing writable
>>> pages. Unless you can solve that - and in a way that keeps Apple
>>> happy if you ever want to deploy such apps - everything else will
>>> be in vein.
>> 
>> I don't think Apple will ever allow that. I don't think Apple will
>> allow executing any code that isn't loaded strictly from disk.
> 
> What do they use themselves for their own webkit JS engine?

My understanding is that they have a special exception for the web browser application to run the "Nitro" javascript engine (a fancy marketing name for JavaScript Core with JIT turned on), but they continue to use JSC with the byte code backend for everything else.  I believe this is what led to the somewhat embarrassing iOS 4.3 situation where "web apps" ran significantly faster in a browser (using JIT), than they did when they were added to the home screen (where they didn't use JIT).  I think that was fixed in 5.0.

Perhaps an iOS guru could provide more details.

Cheers,

Aaron

> 
> -- 
> .marius
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