RFR: Unsafe comparison in ShenandoahHeap::evac_update_oop_ref

[Zhengyu Gu]

Looks good.

-Zhengyu

On 01/24/2018 11:42 AM, Aleksey Shipilev wrote:
> Traversal GC fails in ShenandoahHeap::evac_update_oop_ref when -XX:+VerifyStrictOopOperations is
> enabled, because we need:
> 
> $ hg qdiff
> diff -r 21c595539121 src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp	Wed Jan 24 17:32:27 2018 +0100
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp	Wed Jan 24 17:40:35 2018 +0100
> @@ -151,7 +151,7 @@
>           forwarded_oop = evacuate_object(heap_oop, Thread::current(), evac);
>         }
>         oop prev = atomic_compare_exchange_oop(forwarded_oop, p, heap_oop);
> -      if (prev == heap_oop) {
> +      if (oopDesc::unsafe_equals(prev, heap_oop)) {
>           return forwarded_oop;
>         } else {
>           return NULL;
> 
> This actually affects partial too, which call this method in SVWB.
> 
> Testing: failing test
> 
> Thanks,
> -Aleksey
>