Integrated: 8350483: AArch64: turn on signum intrinsics by default on Ampere CPUs

[Patrick Zhang]

On Sat, 22 Feb 2025 15:27:41 GMT, Patrick Zhang <qpzhang at openjdk.org> wrote:

> Set -XX:+UseSignumIntrinsic by default for Ampere CPUs. It is to fix performance problem found on JMH cases `vm.compiler.Signum|java.lang.*MathBench.sig[nN]um*` where fmov is used to transmit data between GPRs and FPRs with significant time cost.
> 
> Verified on Ampere-1A and found the scores (thrpt, ops/s) of `java.lang.*MathBench.sig[nN]um*` improved 40~50%, while `vm.compiler.Signum._1_signumFloatTest` and `vm.compiler.Signum._3_signumDoubleTest` results gained exponential increases. Also passed GHA sanity checks, and Jtreg tier1 on Ampere-1A as function-wise smoke tests.

This pull request has now been integrated.

Changeset: f529bf71
Author:    Patrick Zhang <qpzhang at openjdk.org>
Committer: Andrew Haley <aph at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/f529bf712d8946584999dfc98abea60c22c97167
Stats:     3 lines in 1 file changed: 3 ins; 0 del; 0 mod

8350483: AArch64: turn on signum intrinsics by default on Ampere CPUs

Reviewed-by: aph

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PR: https://git.openjdk.org/jdk/pull/23735