RFR: 8290892: C2: Intrinsify Reference.reachabilityFence [v2]

[Dean Long]

On Thu, 11 Sep 2025 18:24:46 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> @iwanowww Let me know whenever this is ready to review again 😊
>
> @eme64 I think I addressed/answered all your suggestions/questions. Please, take another look. Thanks!

@iwanowww , do you have a test that shows constant oops are a problem?  My initial impression is that PreserveReachabilityFencesOnConstants shouldn't be needed, because any oops referenced during the compile should go into the ciEnv metadata[] and then into the nmethod oops.  So GC can't reclaim these oops because the nmethod keeps references to them.

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PR Comment: https://git.openjdk.org/jdk/pull/25315#issuecomment-3294254199