RFR: 8365153: AArch64: Set JVM flags for Neoverse N3 and V3 cores

[Evgeny Astigeevich]

On Fri, 8 Aug 2025 14:50:13 GMT, Ruben <duke at openjdk.org> wrote:

> For Neoverse N1, N2, V1, and V2, the following JVM flags are set:
>  - UseSIMDForMemoryOps=true
>  - OnSpinWaitInst=isb
>  - OnSpinWaitInstCount=1
>  - AlwaysMergeDMB=false
> 
> Additionally, for Neoverse V1 and V2 only, these flags are set:
>  - UseCryptoPmullForCRC32=true
>  - CodeEntryAlignment=32
> 
> Set the same flags for Neoverse N3 and V3, respectively.

I checked  V2 and V3 optimization guides:
>    UseSIMDForMemoryOps=true
    OnSpinWaitInst=isb
    OnSpinWaitInstCount=1
    AlwaysMergeDMB=false

I don't see any significant changes in latencies and throughput of instructions used when these options are set.

> UseCryptoPmullForCRC32=true

The latency and throughput are the same.

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PR Comment: https://git.openjdk.org/jdk/pull/26701#issuecomment-3312740477