[jdk17u-dev] Integrated: 8350483: AArch64: turn on signum intrinsics by default on Ampere CPUs

[Patrick Zhang]

On Thu, 27 Feb 2025 06:58:37 GMT, Patrick Zhang <qpzhang at openjdk.org> wrote:

> Backport the commit to set -XX:+UseSignumIntrinsic by default for Ampere CPUs. It is to fix performance problem observed on JMH cases `vm.compiler.Signum|java.lang.*MathBench.sig[nN]um*`.  For example, `vm.compiler.Signum._1_signumFloatTest` thrpt score becomes 30x better on both jdk mainline and jdk17u-dev. The backporting can be very safe as it is limited to Ampere CPUs only and well verified on Ampere-1A with related jmh and jtreg tier1 tests.

This pull request has now been integrated.

Changeset: c5f41eba
Author:    Patrick Zhang <qpzhang at openjdk.org>
Committer: Andrew Haley <aph at openjdk.org>
URL:       https://git.openjdk.org/jdk17u-dev/commit/c5f41eba4dc12fded813d7b6b302cc7a8f0b2e10
Stats:     3 lines in 1 file changed: 3 ins; 0 del; 0 mod

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

Backport-of: f529bf712d8946584999dfc98abea60c22c97167

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PR: https://git.openjdk.org/jdk17u-dev/pull/3300