RFR: 8227085: ZGC: Add on_weak load barrier verification

[Stefan Karlsson]

Thanks, Erik.

StefanK

On 2019-07-02 17:47, Erik Österlund wrote:
> Hi Stefan,
>
> Looks good.
>
> Thanks,
> /Erik
>
> On 2019-07-02 15:47, Stefan Karlsson wrote:
>> Hi all,
>>
>> Please review this patch to add some verification to our on_weak load 
>> barriers.
>>
>> http://cr.openjdk.java.net/~stefank/8227085/webrev.01/
>> https://bugs.openjdk.java.net/browse/JDK-8227085
>>
>> We've had a few bugs where on_weak load barriers have been generated 
>> instead of the normal, on_strong, load barriers. The on_weak barriers 
>> should only be used to read the referent fields of WeakReferences and 
>> SoftReferences. The given oop* is used to calculate the address of 
>> the containing object and check that it is a valid Reference object.
>>
>> This code was tested against the bugs in JDK-8225770 and JDK-8227083.
>>
>> Tested with tier 1-7
>>
>> Thanks,
>> StefanK
>