8321025: Enable Neoverse N1 optimizations for Neoverse V2

[eastig]

As Arm Neoverse V2 will benefit from the same optimizations as Neoverse N1 does, it should have OnSpinWaitInst/OnSpinWaitInstCount defaults set to "isb"/1 and UseSIMDForMemoryOps default set to true.
This patch sets these flags accordingly for the V2 architecture.

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Issue

• JDK-8321025: Enable Neoverse N1 optimizations for Neoverse V2 (Enhancement - P4)

Reviewers

• Nick Gasson (@nick-arm - Reviewer)
• Aleksey Shipilev (@shipilev - Reviewer)

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[eastig]

@nick-arm, could you please have a look?

[openjdk]

@eastig This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8321025: Enable Neoverse N1 optimizations for Neoverse V2

Reviewed-by: ngasson, shade

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 7 new commits pushed to the master branch:

• 62418c6: 8319444: Unhelpful failure output in TestLegalNotices
• cdd1a6e: 8313816: Accessing jmethodID might lead to spurious crashes
• b65ccff: 8320877: Shenandoah: Remove ShenandoahUnloadClassesFrequency support
• b68356b: 8320806: Augment test/langtools/tools/javac/versions/Versions.java for JDK 22 language changes
• d783aa3: 8320940: Fix typo in java.lang.Double
• 43c7f6a: 8320907: Shenandoah: Remove ShenandoahSelfFixing flag
• da7bcfc: 8319935: Ensure only one JvmtiThreadState is created for one JavaThread associated with attached native thread

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
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[shipilev]

Okay in principle, but I have a question, there is another block below:

  // Neoverse V1
  if (_cpu == CPU_ARM && model_is(0xd40)) {
    if (FLAG_IS_DEFAULT(UseCryptoPmullForCRC32)) {
      FLAG_SET_DEFAULT(UseCryptoPmullForCRC32, true);
    }
  }

Should it be enabled for V2 as well?

[eastig]

Okay in principle, but I have a question, there is another block below:

  // Neoverse V1
  if (_cpu == CPU_ARM && model_is(0xd40)) {
    if (FLAG_IS_DEFAULT(UseCryptoPmullForCRC32)) {
      FLAG_SET_DEFAULT(UseCryptoPmullForCRC32, true);
    }
  }

Should it be enabled for V2 as well?

Good catch. I'll check whether V2 has the same or better pmull as V1.

[shipilev]

Good catch. I'll check whether V2 has the same or better pmull as V1.

Although, it would not be "enabling N1 optos for V2", it would be "enabling V1 optos for V2" :)
Your call if you just want to make that change separately.

[eastig]

UseCryptoPmullForCRC32

According to the V2 optimization guide pmull is the same in V2 as in V1. So UseCryptoPmullForCRC32 should be enabled for V2 as well.

I'd do this in a separate PR to allow this change to be backported to jdk11u. There is no UseCryptoPmullForCRC32 in jdk11u.

[eastig]

Created https://bugs.openjdk.org/browse/JDK-8321105

[eastig]

/integrate

[eastig]

Thanks @shipilev @nick-arm for the review.

[openjdk]

Going to push as commit c9d15f7.
Since your change was applied there have been 20 commits pushed to the master branch:

• 61653a1: 8320830: [AIX] Dont mix os::dll_load() with direct dlclose() calls
• 8b102ed: 8321063: AArch64: Zero build fails after JDK-8320368
• 6941369: 8320921: GHA: Parallelize hotspot_compiler test jobs
• 0d14636: 8320515: assert(monitor->object_peek() != nullptr) failed: Owned monitors should not have a dead object
• d6b4aa0: 8318157: RISC-V: implement ensureMaterializedForStackWalk intrinsic
• 7766785: 8319372: C2 compilation fails with "Bad immediate dominator info"
• 940f67c: 8318854: [macos14] Running any AWT app prints Secure coding warning
• c864317: 8320888: Shenandoah: Enable ShenandoahVerifyOptoBarriers in debug builds
• d1e73b1: 8318626: GetClassFields does not filter out ConstantPool.constantPoolOop field
• ea6e92e: 8320945: problemlist tests failing on latest Windows 11 update
• ... and 10 more: https://git.openjdk.org/jdk/compare/a2c5f1fc914ef5c28d044b75598f895cf6097138...master

Your commit was automatically rebased without conflicts.

[openjdk]

@eastig Pushed as commit c9d15f7.

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