Subject text

[Tom Rodriguez]

Accidentally pushed send too early.  Ignore for now.

tom

On Mar 25, 2011, at 1:38 PM, Tom Rodriguez wrote:

> 6378256: Performance problem with System.identityHashCode in client compiler
> Reviewed-by:
> 
> The hashCode for an object can often be grabbed directly from the
> header instead of going into the runtime and C1 has an existing
> optimization for Object.hashCode.  System.identityHashCode is the same
> as calling Object.hashCode directly and should have the same
> optimization.  The fix is to use the same trick for identityHashCode
> as is being used for Object.hashCode with the addition of a null
> check.  Doing this is 10 times faster.  Tested with test case from
> report.  I also added an implementation for x86_64 which is just a
> straight copy of the x86_32 code.  I put it under !TIERED since in the
> tiered world the extra code just makes the C2 version slightly slower.
> 
> As an aside, C2 implements Object.hashCode using a vtable check to deal
> with the potential overloading.
>