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?
Yes. But it requires two CASes in a row. Don't know if that is better than our loop, which is rarely even entered (normally the CAS-construct goes via fast-path with a single CAS). Roman
