I was hoping that getting the compiler to emit different stuff would help
the JITs. But it sounds like in this case hand-optimizing as you are doing
makes the most sense, if it is one big and important switch at the core.

What does the 40% on Android mean? What is compared to what?

- Alon



On Sun, Dec 22, 2013 at 12:37 PM, <[email protected]> wrote:

> I got it a lot faster by breaking up the switch statement manually (Around
> 4x - 5x). Interestingly, even though this is quite CPU-heavy code
> (emulation) the difference between Chrome and Firefox is marginal (Around
> 10%)
>
> Outlining does not seem to help, neither with compilation speed nor run
> speed.
>
> I compile with normal optimizations (-O2) and no extra flags that may slow
> things down as far as I know.
>
> Have not checked the useIfs-thing, becuase this was a JIT problem and that
> seems to be about the compiler. Also, my switch statement has close to 256
> statements so I don't think it applies anyway.
>
> -- Sasq
>
> On Sunday, December 22, 2013 12:11:39 AM UTC+1, azakai wrote:
>
>> Yes, outliner is one option here. If that doesn't help, you can manually
>> change the heuristics for switches vs ifs in the compiler, look for
>> `useIfs` in src/jsifier.js.
>>
>> Was this with optimizations on, or not?
>>
>> - Alon
>>
>>
>>
>> On Sat, Dec 21, 2013 at 2:35 PM, Sören Balko <[email protected]> wrote:
>>
>>> Why don't you change the source to split up that single large switch
>>> statement across multiple functions? The Chrome profiler should then tell
>>> you if that was effective, no? You could also try Alon's outlining feature
>>> and see if that does the trick without touching the source. I think this
>>> was introduced to split large functions into smaller ones in order to make
>>> it easier (and faster) for JITs to optimize the code.
>>>
>>>
>>> Am Samstag, 21. Dezember 2013 20:11:10 UTC+10 schrieb [email protected]:
>>>
>>>> So the SID-chip/C64 emulation part of my music player runs very slow -
>>>> about 10x native. Checking in the Chrome profiler I see that the main
>>>> function has an exclamation mark with:
>>>> Not Optimized: SwitchStatement: Too many clauses
>>>>
>>>> The 6510 emulation core is one big switch statement, so this is true. I
>>>> realize this is a JIT problem but I wonder if you can get the emscripten
>>>> compiler to help in this situation?
>>>>
>>>> Otherwise maybe I can try breaking it up manually, but would that help?
>>>>
>>>> -- Sasq
>>>>
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