RFR (sh/jdk8): Backport: JDK-8231086: Shenandoah: Stronger invariant for object-arraycopy

[Roman Kennke]

Hi Aleksey,

>> http://cr.openjdk.java.net/~rkennke/JDK-8231086-jdk8/webrev.01/
> 
> Okay, brief look:
> 
> *) src/cpu/aarch64/vm/stubGenerator_aarch64.cpp
>    src/cpu/x86/vm/stubGenerator_x86_32.cpp
> 
>  Should new switch cases be protected by  #if INCLUDE_ALL_GCS too?

Good question. It wasn't before, and it isn't for the other GCs. Also,
the enum that defines this doesn't have INCLUDE_ALL_GCS either. I think
we might risk compiler complains about missing cases?

> *) ShenandoahBarrierSet::arraycopy_pre_work implementation: indenting is off, is this from original
> changeset?

No. Fixed.

> *) I believe test is misplaced. Did that test even run?
>   test/hotspot/jtreg/gc/shenandoah/compiler/TestClone.java
> should be
>   test/gc/shenandoah/compiler/TestClone.java

Oopsie. Right.

http://cr.openjdk.java.net/~rkennke/JDK-8231086-jdk8/webrev.02/

Better?

Thanks,
Roman