RFR: 8204474: Have instanceRefKlass use HeapAccess when loading the referent

[Erik Osterlund]

Hi Per,

Looks good.

Thanks,
/Erik

> On 6 Jun 2018, at 16:16, Per Liden <per.liden at oracle.com> wrote:
> 
> Hi,
> 
> To support concurrent reference processing in ZGC, instanceRefKlass::try_discover() can no longer use RawAccess to load the referent field. Instead it should use
> 
>  HeapAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>
> 
> or
> 
>  HeapAccess<ON_WEAK_OOP_REF | AS_NO_KEEPALIVE>
> 
> depending on the reference type. This patch also adjusts InstanceRefKlass::trace_reference_gc() for the same reason.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8204474
> Webrev: http://cr.openjdk.java.net/~pliden/8204474/webrev.0
> 
> Testing: This patch has been part of the ZGC repository for quite some time and gone through various testing, including tier{1,2,3,4,5,6} in mach5.
> 
> /Per