8275645: [JVMCI] avoid unaligned volatile reads on AArch64

[dougxc]

This PR updates c2v_readFieldValue to always do the field read with volatile semantics but without using a volatile read instruction directly to avoid platform specific issues with unaligned reads (e.g., an unaligned ldar on AArch64 causes a SIGBUS).

---

Progress

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

Issue

• JDK-8275645: [JVMCI] avoid unaligned volatile reads on AArch64

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer)
• Tom Rodriguez (@tkrodriguez - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/6044/head:pull/6044
$ git checkout pull/6044

Update a local copy of the PR:
$ git checkout pull/6044
$ git pull https://git.openjdk.java.net/jdk pull/6044/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 6044

View PR using the GUI difftool:
$ git pr show -t 6044

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/6044.diff

[bridgekeeper]

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[openjdk]

@dougxc The following label will be automatically applied to this pull request:

• hotspot-compiler

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[mlbridge]

Webrevs

• 00: Full (2accdf7a)

[openjdk]

@dougxc 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:

8275645: [JVMCI] avoid unaligned volatile reads on AArch64

Reviewed-by: kvn, never

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 36 new commits pushed to the master branch:

• 4e647aa: 8275416: G1: remove unnecessary make_referent_alive in precleaning phase
• dd622e5: 8275783: G1: fix incorrect region type documentation in HeapRegionType
• b2128a9: 8263155: Allow additional contents for DMG
• 1efe946: 8275712: Hashtable literal_size functions are broken
• fab3d6c: 8275761: Backout: JDK-8274794 Print all owned locks in hs_err file
• c978ca8: 8275344: -Xcheck:jni produces some warnings in the LCMS.c
• 6a466fe: 8202056: Expand serial warning to check for bad overloads of serial-related methods and ineffectual fields
• 4e9dd4b: 8275384: Change nested classes in jdk.jconsole to static nested classes
• 0961de4: 8275347: ciReplay: staticfield lines not properly terminated
• 7dd8237: 8275084: CDS warning when building with LOG=debug
• ... and 26 more: https://git.openjdk.java.net/jdk/compare/043cde22d4d6bd975e75daa9ad52770cf79df934...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.

[dougxc]

Thanks for the reviews @vnkozlov and @tkrodriguez.

[dougxc]

/integrate

[openjdk]

Going to push as commit 4dec8fc.
Since your change was applied there have been 36 commits pushed to the master branch:

• 4e647aa: 8275416: G1: remove unnecessary make_referent_alive in precleaning phase
• dd622e5: 8275783: G1: fix incorrect region type documentation in HeapRegionType
• b2128a9: 8263155: Allow additional contents for DMG
• 1efe946: 8275712: Hashtable literal_size functions are broken
• fab3d6c: 8275761: Backout: JDK-8274794 Print all owned locks in hs_err file
• c978ca8: 8275344: -Xcheck:jni produces some warnings in the LCMS.c
• 6a466fe: 8202056: Expand serial warning to check for bad overloads of serial-related methods and ineffectual fields
• 4e9dd4b: 8275384: Change nested classes in jdk.jconsole to static nested classes
• 0961de4: 8275347: ciReplay: staticfield lines not properly terminated
• 7dd8237: 8275084: CDS warning when building with LOG=debug
• ... and 26 more: https://git.openjdk.java.net/jdk/compare/043cde22d4d6bd975e75daa9ad52770cf79df934...master

Your commit was automatically rebased without conflicts.

[openjdk]

@dougxc Pushed as commit 4dec8fc.

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