[foreign-preview] RFR: 8286306: Upcall wrapper class sharing

[Maurizio Cimadamore]

On Fri, 6 May 2022 14:50:53 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> This patch adds upcall wrapper class sharing.
> 
> I recently realized that these classes can be shared if they have the same input FunctionDescriptor, but a different target method handle.
> 
> This is implemented by generating a wrapper class that takes the target method handles as a leading argument. The target method handle is then inserted into the parameter list using `MethodHandles::insertArguments` to create the final method handle that is returned by the specializer. After MH customization kicks in, the target will be a constant again (so shouldn't affect peak performance).
> 
> Doing this doesn't effect peak performance, as verified through the Upcalls benchmark, but does significantly improve linking performance.
> 
> Before:
> 
>     Benchmark              Mode  Cnt   Score   Error  Units
>     LinkUpcall.link_blank  avgt   30  69.323 � 2.522  us/op
> 
> After:
> 
>     Benchmark              Mode  Cnt   Score   Error  Units
>     LinkUpcall.link_blank  avgt   30  11.787 � 0.744  us/op

Looks solid!

-------------

Marked as reviewed by mcimadamore (Committer).

PR: https://git.openjdk.java.net/panama-foreign/pull/679