RFR: 8298427: Detect Ampere-1 and Ampere-1A CPUs and set default options

[Andrew Haley]

On Fri, 6 Jan 2023 08:27:28 GMT, Patrick Zhang <qpzhang at openjdk.org> wrote:

> This patch is to add CPU detection for Ampere-1 and Ampere-1A and set -XX:+UseSIMDForMemoryOps by default. In addition, an `enum Ampere_CPU_Model ` got introduced in order to clearly describe all Ampere CPUs in `src/hotspot/cpu/aarch64/vm_version_aarch64.hpp`.
> 
> Tests done:
> 1. Jtreg tier1 sanity check on Ampere Altra AArch64 platforms, and Ampere-1 systems as well. No new issue found.
> 4. GitHub Actions (GHA) sanity tests: https://github.com/cnqpzhang/jdk/actions/runs/3845722221
> 3. OpenJDK bundled JMH, `make run-test TEST="micro:java.lang.ArrayCopy*" `, SIMD vs NoSIMD ratios are mostly positive. For example, `java.lang.ArrayCopyAligned.testChar` with `-p length=600` showed +42% improvement on Ampere-1. 
> 2. Ran [JMH JDK Microbenchmarks](https://github.com/openjdk/jmh-jdk-microbenchmarks), ~1500 cases. No obvious perf regression found.
> 
> Signed-off-by: Patrick Zhang <patrick at os.amperecomputing.com>

Please update the title to  

8298427: AArch64: Detect Ampere-1 and Ampere-1A CPUs and set default options

Reason: AArch64 reviewers look for AArch64-related bugs. They'll see your PR sooner.

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Marked as reviewed by aph (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11878