RFR: 8298472: AArch64: Detect Ampere-1 and Ampere-1A CPUs and set default options [v2]

[Nick Gasson]

On Fri, 6 Jan 2023 09:39:19 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>
>
> Patrick Zhang has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
> 
>   8298472: Detect Ampere-1 and Ampere-1A CPUs and set default options
>   
>   Signed-off-by: Patrick Zhang <patrick at os.amperecomputing.com>

Marked as reviewed by ngasson (Reviewer).

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