8271862: C2 intrinsic for Reference.refersTo() is often not used

[shipilev]

Clean backport to make JDK 16 introduced feature more compelling with a workaround.

Additional testing:

• Linux x86_64 fastdebug, RefersTo tests pass

RefersTo tests:

./test/hotspot/jtreg/gc/TestReferenceRefersTo.java
./test/hotspot/jtreg/gc/TestReferenceRefersToDuringConcMark.java
./test/hotspot/jtreg/gc/shenandoah/TestReferenceRefersToShenandoah.java
./test/hotspot/jtreg/compiler/intrinsics/TestReferenceRefersTo.java
./test/jdk/java/lang/ref/ReferenceRefersTo.java

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8271862: C2 intrinsic for Reference.refersTo() is often not used

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk17u pull/62/head:pull/62
$ git checkout pull/62

Update a local copy of the PR:
$ git checkout pull/62
$ git pull https://git.openjdk.java.net/jdk17u pull/62/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 62

View PR using the GUI difftool:
$ git pr show -t 62

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk17u/pull/62.diff

[bridgekeeper]

👋 Welcome back shade! 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 backport pull request has now been updated with issue from the original commit.

[openjdk]

@shipilev This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8271862: C2 intrinsic for Reference.refersTo() is often not used

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 20 new commits pushed to the master branch:

• cef269f: 8270317: Large Allocation in CipherSuite
• 9f7de59: 8263773: Reenable German localization for builds at Oracle
• 6a7542f: 8272973: Incorrect compile command used by TestIllegalArrayCopyBeforeInfiniteLoop
• f1c8fa6: 8271121: ZGC: stack overflow (segv) when -Xlog:gc+start=debug
• d561554: 8270110: Shenandoah: Add test for JDK-8269661
• c96cfed: 8270171: Shenandoah: Cleanup TestStringDedup and TestStringDedupStress tests
• f32703f: 8272783: Epsilon: Refactor tests to improve performance
• 0ced2aa: 8272473: Parsing epoch seconds at a DST transition with a non-UTC parser is wrong
• ea6e678: 8271560: sun/security/ssl/DHKeyExchange/LegacyDHEKeyExchange.java still fails due to "An established connection was aborted by the software in your host machine"
• 271403b: 8269031: linux x86_64 check for binutils 2.25 or higher after 8265783
• ... and 10 more: https://git.openjdk.java.net/jdk17u/compare/648f3f6a8fe9ea2e00b60710afa44208cfbc2c49...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[mlbridge]

Webrevs

• 00: Full (a94cff59)

[shipilev]

Got the push approval.

/integrate

[openjdk]

Going to push as commit bf788ee.
Since your change was applied there have been 34 commits pushed to the master branch:

• 92ff652: 8272970: Parallelize runtime/InvocationTests/
• c2dc88f: 8272850: Drop zapping values in the Zap* option descriptions
• fc8078a: 8263375: Support stack watermarks in Zero VM
• 759cbcb: 8272838: Move CriticalJNI tests out of tier1
• da1c0fe: 8272639: jpackaged applications using microphone on mac
• 20be766: 8271722: [TESTBUG] gc/g1/TestMixedGCLiveThreshold.java can fail if G1 Full GC uses >1 workers
• f8ecff4: 8269951: [macos] Focus not painted in JButton when setBorderPainted(false) is invoked
• 808356a: 8273358: macOS Monterey does not have the font Times needed by Serif
• ec0b85a: 8273593: [REDO] Warn user when using mac-sign option with unsigned app-image.
• 4dff991: 8269687: pauth_aarch64.hpp include name is incorrect
• ... and 24 more: https://git.openjdk.java.net/jdk17u/compare/648f3f6a8fe9ea2e00b60710afa44208cfbc2c49...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit bf788ee.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.