RFR: 8368303: AlwaysAtomicAccesses is excessively strict [v2]

[Dean Long]

On Thu, 2 Oct 2025 17:14:41 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> In C1, the experimental flag `AlwaysAtomicAccesses` treats accesses to all fields as if they were volatile fields. This is correct but excessive: we only need single-copy atomicity to satisfy `AlwaysAtomicAccesses`. 
>> 
>> We need this in order to allow progress on JDK-8365147.
>
> Andrew Haley has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Next try

Marked as reviewed by dlong (Reviewer).

src/hotspot/share/gc/shared/c1/barrierSetC1.cpp line 45:

> 43: // The JMM requires atomicity for all accesses to fields of primitive
> 44: // types other than double and long. In practice, HotSpot assumes that
> 45: // on all all processors, accesses to memory operands of wordSize and

Suggestion:

// on all processors, accesses to memory operands of wordSize and

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PR Review: https://git.openjdk.org/jdk/pull/27432#pullrequestreview-3296669072
PR Review Comment: https://git.openjdk.org/jdk/pull/27432#discussion_r2400254515