RFR: JDK-8221766: Load-reference barriers for Shenandoah

Andrew Haley aph at redhat.com
Mon Apr 8 08:28:59 UTC 2019


On 4/7/19 7:18 PM, Roman Kennke wrote:
> On 4/2/19 10:12 PM, Roman Kennke wrote:
>>> - No more need for object equals barriers.
>>
>> I'm pleased about that. I really hated the AArch64 Shenandoah CAS!
> 
> I'm sorry to disappoint you, but the CAS barrier is still needed. The
> memory location may still legally hold a from-space reference, and
> comparing that to a to-space reference needs some special care. And
> yes, ZGC has a similar problem as far as I know.

That's interesting. Could we not simply promote the reference in the
reference field we're CASing, then do a normal CAS?

-- 
Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
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