RFR: 8364936: Shenandoah: Switch nmethod entry barriers to conc_instruction_and_data_patch [v3]

[Dingli Zhang]

On Wed, 3 Sep 2025 00:37:59 GMT, Cesar Soares Lucas <cslucas at openjdk.org> wrote:

>> Please, review this patch to make nmethod entry barriers use `conc-instruction-and-data-patch` fence mechanics when ShenandoahGC is being used on AArch64. The patch also removes (including from JVMCI interface) the old constant that was being used only by Shenandoah on AArch64.
>> 
>> The patch has been tested with functional and performance benchmarks on AArch64. Improvements in DaCapo and Renaissance benchmarks can be as high as 30%. Maximum critical Jops in SPEC improved by ~10%.
>
> Cesar Soares Lucas has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Make PPC backend to also use concurrent code patching.

LGTM, thanks!

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Marked as reviewed by dzhang (Author).

PR Review: https://git.openjdk.org/jdk/pull/26999#pullrequestreview-3178728761