RFR: 8232613: Move Object.registerNatives into HotSpot

[David Holmes]

Hi Claes,

My only nit with this is that I don't think register_native and friends 
belongs in the SystemDictionary class as it has nothing to do with the 
SD. This code seems to be all about Methods so that seems like the place 
to put this.

Thanks,
David

On 22/10/2019 12:55 am, Claes Redestad wrote:
> Hi,
> 
>   Object.java currently registers various native functions via the
> registerNatives facility.
> 
>      private static native void registerNatives();
>      static {
>          registerNatives();
>      }
> 
> Not costly in and off itself, but this has the side effect that these
> two methods are taken into account every time the VM has to generate
> default methods and overpasses for some class during class load, which
> can take up substantial time. When prototyping JDK-8219713[1],
> explicitly excluding these two methods showed some improvement to
> default method generation, but adding special cases to the logic was
> decided against.
> 
> If we instead can get rid of the Object <clinit> and the registerNatives
> altogether we get the same (or a slightly better) speedup. This
> effectively reduces memory use and instructions retired doing default
> method generation by 3-5%.
> 
> Webrev: http://cr.openjdk.java.net/~redestad/8232613/open.00/
> Bug:    https://bugs.openjdk.java.net/browse/JDK-8232613
> 
> Testing:
> - tier1-7
> - Added a test which naively redefines Object and ensures native methods
> keep working
> 
> Thanks!
> 
> /Claes