8355644: Optimize Math.cbrt for AArch64 platforms with an intrinsic implementation

[theRealAph]

This is the AArch64 version of the cbrt intrinsic. Unfortunately, it doesn't provide much of an advantage over C2-compiled Java, so it's not worth doing.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Warnings

 ⚠️ Patch contains a binary file (src/java.desktop/share/classes/java/awt/doc-files/BorderLayout-1.gif)
 ⚠️ Patch contains a binary file (src/java.desktop/share/classes/java/awt/doc-files/FlowLayout-1.gif)
 ⚠️ Patch contains a binary file (src/java.desktop/share/classes/java/awt/doc-files/GridBagLayout-1.gif)
 ⚠️ Patch contains a binary file (src/java.desktop/share/classes/java/awt/doc-files/GridBagLayout-2.gif)
 ⚠️ Patch contains a binary file (src/java.desktop/share/classes/java/awt/doc-files/GridLayout-1.gif)
 ⚠️ Patch contains a binary file (src/java.desktop/share/classes/java/awt/doc-files/GridLayout-2.gif)
 ⚠️ Patch contains a binary file (test/hotspot/jtreg/runtime/ClassFile/JsrRewritingTestCase.jar)
 ⚠️ Patch contains a binary file (test/hotspot/jtreg/runtime/ClassFile/testcase.jar)

Issue

• JDK-8355644: Optimize Math.cbrt for AArch64 platforms with an intrinsic implementation (Enhancement - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/25085/head:pull/25085
$ git checkout pull/25085

Update a local copy of the PR:
$ git checkout pull/25085
$ git pull https://git.openjdk.org/jdk.git pull/25085/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 25085

View PR using the GUI difftool:
$ git pr show -t 25085

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/25085.diff

[bridgekeeper]

👋 Welcome back aph! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@theRealAph The following labels will be automatically applied to this pull request:

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• graal
• hotspot
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[theRealAph]

The reason for the speed difference is worth a remark here. The intrinsic for x86 gets its advantage over the Java code in the JDK by avoiding divide instructions altogether. Apple M silicon can issue a divide instruction every cycle, so this advantage turns into a disadvantage, because the algorithm using division has fewer instructions than this intrinsic. One Arm Neoverse silicon, which does not have super-fast floating-point division, there is an advantage, but it's really only a small one. See the Bug for more details.

[openjdk]

@theRealAph this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout JDK-8355644
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[bridgekeeper]

@theRealAph This pull request has been inactive for more than 8 weeks and will be automatically closed if another 8 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!