[jdk17u-dev] RFR: 8298472: AArch64: Detect Ampere-1 and Ampere-1A CPUs and set default options [v2]

[Goetz Lindenmaier]

On Tue, 31 Jan 2023 06:25:45 GMT, Patrick Zhang <qpzhang at openjdk.org> wrote:

>> Backport of CPU detection function for Ampere-1 and Ampere-1A, and performance enhancement with turning on UseSIMDForMemoryOps option for these two CPUs by default. Verified OpenJDK bundled JMH test cases, `make run-test TEST="micro:java.lang.ArrayCopy*"` , SIMD vs NoSIMD ratios are mostly positive as expected, aligned with that on jdk mainline. Low risk to other functions/systems due to the CPU detection logic.
>> 
>> Not a clean backport, manually resolved below conflicts, **no function change**:
>> 1. Copyright years are `1997, 2021` in 17u-dev instead of the expected `1997, 2022` in two files
>> 2. `@@ -132,7 +132,7 @@ void VM_Version::initialize()` should be 131 for 17u-dev
>> 3. `@@ -144,6 +144,13 @@ void VM_Version::initialize() ` should be 143 for 17u-dev
>> 4. The `enum Feature_Flag` in 17u-dev has been updated in jdk mainline to: declaring the macro `#define CPU_FEATURE_FLAGS` firstly then wrapping it inside the enum. So the line numbers are not aligned during doing `git apply`
>> 
>> FYI, a try-out: manually fixing these conflicts according to `git apply -v` in the patch file can make it applied cleanly. 
>> 
>> Additional tests done:
>> 1. Linux aarch64 release tier1 on Ampere-1 system, without explicitly specifying UseSIMDForMemoryOps 
>> 6. OpenJDK GHA Sanity Checks on forked repo: https://github.com/cnqpzhang/jdk17u-dev/actions/runs/3919027362
>> 
>> Backport-of: 706845743699efb01994e2d12c65023a3e972b77
>> Signed-off-by: Patrick Zhang <patrick at os.amperecomputing.com>
>
> Patrick Zhang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:
> 
>  - Merge branch 'master' into JDK-8298472-ampere-simd-memops
>  - 8298472: AArch64: Detect Ampere-1 and Ampere-1A CPUs and set default options
>    
>    Backport-of: 706845743699efb01994e2d12c65023a3e972b77
>    Signed-off-by: Patrick Zhang <patrick at os.amperecomputing.com>

Hi, please see
https://mail.openjdk.org/pipermail/jdk-updates-dev/2023-January/020064.html
https://wiki.openjdk.org/display/JDKUpdates/How+to+contribute+or+backport+a+fix

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PR: https://git.openjdk.org/jdk17u-dev/pull/1067