RFR(sh/jdk8): [backport] 8241765: Shenandoah: AARCH64 need to save/restore call clobbered registers before calling keepalive barrier

[Zhengyu Gu]

Looks fine.

-Zhengyu

On 12/1/20 2:40 PM, Roman Kennke wrote:
> This backports the fix for:
> https://bugs.openjdk.java.net/browse/JDK-8241765
> 
> It is relatively straightforward, except that it has to be done in 
> shared (with G1) code path:
> 
> http://cr.openjdk.java.net/~rkennke/JDK-8241765-jdk8/webrev.00/
> 
> Testing: hotspot_gc_shenandoah
> 
> Ok?
> 
> Thanks, Roman
>