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

[Per Liden]

Thanks for reviewing, Erik!

/Per

On 2018-06-06 18:27, Erik Osterlund wrote:
> 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
>