Ping: RFR: JDK-8205523: Explicit barriers for interpreter

[Roman Kennke]

> Hi all,
> 
> A number of operations cannot reasonably make use of the Access API but
> require explicit read- and write-barriers for GCs like Shenandoah that
> need to ensure to-space consistency. Examples are monitor-enter/-exit
> and some intrinsics.
> 
> The change adds APIs to BarrierSetAssembler (x86 and aarch64) to support
> these kinds of explicit barriers, and the necessary calls in relevant
> places. The default implementation does nothing. These barriers have
> been found and tested over several years in Shenandoah.
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8205523
> Webrev:
> http://cr.openjdk.java.net/~rkennke/JDK-8205523/webrev.00/
> 
> Testing: hotspot/tier1, will submit into Mach5 after reviews.
> 
> Can I please get reviews?
> 
> Thanks, Roman
>