RFR: 8324824: AArch64: Detect Ampere-1B core and update default options for Ampere CPUs

[Dean Long]

On Tue, 6 Feb 2024 07:13:22 GMT, Patrick Zhang <qpzhang at openjdk.org> wrote:

> Added CPU detection for Ampere-1B, and updated the default options for AmpereOne, Ampere-1A/1B to have `-XX:+UseSIMDForMemoryOps` and `-XX:OnSpinWaitInst=isb -XX:OnSpinWaitInstCount=2`.
> 
> Tests done:
> 1. GitHub Actions (GHA) sanity tests: https://github.com/cnqpzhang/jdk/actions/runs/7786881426
> 2. OpenJDK bundled JMH, `make run-test TEST="jtreg:hotspot/jtreg/compiler/onSpinWait*"` , `make run-test TEST="micro:ThreadOnSpinWait*"`, no issue found, and `ThreadOnSpinWaitProducerConsumer.trial` showed ~3x better scores (us/op).
> 3. Jtreg tier1/tier2 sanity check on AmpereOne AArch64 platforms, Ampere-1A systems as well, no new issues found.
> 
> Signed-off-by: Patrick Zhang [patrick at os.amperecomputing.com](mailto:patrick at os.amperecomputing.com)

Normally I would say that this looks trivial, but Oracle was recently bit by JDK-8325264, because aarch64 changes in JDK-8324724 caused problems on macos-aarch64, and for some reason github testing did not catch the problem.

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PR Comment: https://git.openjdk.org/jdk/pull/17722#issuecomment-1931179843