[Webkit-unassigned] [Bug 161409] [JSC] Implement parsing of Async Functions

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=161409

--- Comment #7 from Yusuke Suzuki <utatane.tea at gmail.com> ---
(In reply to comment #6)
> So, experimenting with this a bit, I'm finding that those "expensive
> branches" identified by Yusuke Suzuki can be (mostly) mitigated in the
> benchmarks by moving their contents to never-inlined functions. I guess this
> makes the on-stack allocation for the more commonly executed code smaller,
> and means the only extra work the "commonly executed" code has to do is the
> interned string comparison (testing if a particular string is "async" or
> not), which should be pretty cheap.
> 
> The biggest one of these in the jQuery benchmark is, according to
> Instruments.app, the one in parseStatement(). Uninlining these rare branches
> might be a good way to go, but I'd appreciate a second set of eyes measuring
> that solution using different tools and settings as well.
> 
> Some benchmark runs (just with jquery) with 4 VM runs and 10 inner runs:
> 
> ```
> Collected 40 samples per benchmark/VM, with 4 VM invocations per benchmark.
> Emitted a call to
> gc() between sample measurements. Used 1 benchmark iteration per VM
> invocation for warm-up. Used
> the jsc-specific preciseTime() function to get microsecond-level timing.
> Reporting benchmark
> execution times with 95% confidence intervals in milliseconds.
> 
> 1)
>                          Baseline                  Patched                  
> 
> 
> jquery               6.76557+-0.13436    ?     6.89083+-0.08124       ?
> might be 1.0185x slower
> 
> <geometric>          6.76557+-0.13436    ?     6.89083+-0.08124       ?
> might be 1.0185x slower
> 
> 2)
>                          Baseline                  Patched                  
> 
> 
> jquery               7.06592+-0.09167          7.03025+-0.07808       
> 
> <geometric>          7.06592+-0.09167          7.03025+-0.07808        
> might be 1.0051x faster
> ```
> 
> So, I dunno, that seems like an improvement over the existing regression to
> me.

Great! Did you already upload the updated patch?

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