[dev-jonghoonpark]

related jira issue: https://bugs.openjdk.org/browse/JDK-8367717

Changes

• deleted all definitions of atomic_copy64
• replaced all calls to atomic_copy64 with AtomicAccess::store(dst, AtomicAccess::load(src))

Verification

• Verified by running:
  • make run-test TEST="gtest:StubRoutines*"
  • make run-test TEST="gtest:AtomicAccess*"

Please let me know if there are any additional or more appropriate verification steps I should perform.

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Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed (2 reviews required, with at least 1 Reviewer, 1 Author)

Issue

• JDK-8367717: Cleanup atomic_copy64 (Enhancement - P4)

Reviewers

• Kim Barrett (@kimbarrett - Reviewer)
• David Holmes (@dholmes-ora - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/27642/head:pull/27642
$ git checkout pull/27642

Update a local copy of the PR:
$ git checkout pull/27642
$ git pull https://git.openjdk.org/jdk.git pull/27642/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 27642

View PR using the GUI difftool:
$ git pr show -t 27642

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/27642.diff

Using Webrev

Link to Webrev Comment

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8367717: Cleanup atomic_copy64

Reviewed-by: kbarrett, dholmes

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At the time when this comment was updated there had been 4 new commits pushed to the master branch:

• ee33ee4: 8395709: RISC-V: Consolidate C2 scalar CMove match rules
• be3ca50: 8395706: RISC-V: Avoid redundant copies when converting long values to pointers
• e2d940b: Merge
• ... and 1 more: https://git.openjdk.org/jdk/compare/fd8089e571c098eb59036be7e7ae60cc54c4170c...master

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[mlbridge]

Webrevs

• 03: Full - Incremental (a31c2daf)
• 02: Full - Incremental (801f9b45)
• 01: Full - Incremental (de15f195)
• 00: Full (33a93805)

[kimbarrett]

As described in the issue, this change aligns atomic_copy64 definitions for
zero platforms with those of other platforms.

The issue suggests it might be better to replace calls to atomic_copy64 with
AtomicAccess::store(dst, AtomicAccess::load(src)) (using the new
AtomicAccess nomenclature), and then delete all definitions of
atomic_copy64. And there's a comment agreeing with that suggestion. I think
that's the way to go, rather than what this PR proposes.

[dev-jonghoonpark]

@kimbarrett

Thanks for the feedback.
I thought the plan was to align the definitions first, and then implement the new form later.
I'll revise the work to make the change to the new formulation, as you suggested.

[jcking]

This partially fixes https://bugs.openjdk.org/browse/JDK-8369207 as well, but this only does it for jlong. I can wait for this to go in, and then update jshort and jint to use AtomicAccess as well or we can do it all in this PR.

[kimbarrett]

This partially fixes https://bugs.openjdk.org/browse/JDK-8369207 as well, but this only does it for jlong. I can wait for this to go in, and then update jshort and jint to use AtomicAccess as well or we can do it all in this PR.

@jcking - I noticed that problem too, while reviewing this change. I don't care
whether it is fixed in this PR or in yours.

Note that your's currently doesn't perform atomic accesses on the "from"
value. I think that's wrong, since the documentation for these functions
doesn't indicate atomicity only for the store. The comment in copy.hpp says
"atomicity: atomic or non-atomic on the copy unit." I take that to mean both
source and destination.

Your PR is also not addressing other platforms with similar issues, such as in
copy_ppc.hpp.

Also, this all begs the question of why we have four different copies of these
functions - bsd_aarch64, bsd_zero, linux_aarch64, and linux_zero. All of these
should be identical.

Basically, I think the Copy class is kind of a mess, and that discourages its
use. Probably this needs an overall plan of attack (broken up into reviewable
chunks, but with an overarching goal), rather than piecemeal fixups.

[jcking]

@kimbarrett

Proposal, should we do something similar to AtomicAccess? Provide default naive implementations and let each platform specialize?

[kimbarrett]

@jcking I think AtomicAccess mostly already has platform-specific specializations. A case where it doesn't
is the bitops, but there we have a default naive implementation, with the intent that platforms will (eventually)
specialize. There's one of those efforts being reviewed now (for ppc).

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[dev-jonghoonpark]

The discussion seems unresolved, so I’ll convert this PR back to draft for now.

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[dholmes-ora]

@dev-jonghoonpark Can we re-open this as-is and keep the scope simply to replacing atomic_copy64 with the AtomicAccess load and store operations.

[dev-jonghoonpark]

Sorry for the late reply, I missed your comment.
I’ll update the branch with the latest master and follow up.

/open

[openjdk]

@dev-jonghoonpark This pull request is now open

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[kimbarrett]

I agree with @dholmes-ora, this change looks fine in its current form
(except the copyrights need to be updated now). There are followups
that can be done for further improvement, but this is a good
incremental change.

[dev-jonghoonpark]

@kimbarrett Thanks for checking. I’ve updated the copyright. Could you please re-review and approve?

[kimbarrett]

still good.

[dholmes-ora]

LGTM2. Thanks

(Nice to hear from you @kimbarrett !)

[dev-jonghoonpark]

/integrate

[openjdk]

@dev-jonghoonpark
Your change (at version a31c2da) is now ready to be sponsored by a Committer.

[dholmes-ora]

/sponsor

[openjdk]

Going to push as commit ec081d9.
Since your change was applied there have been 4 commits pushed to the master branch:

• ee33ee4: 8395709: RISC-V: Consolidate C2 scalar CMove match rules
• be3ca50: 8395706: RISC-V: Avoid redundant copies when converting long values to pointers
• e2d940b: Merge
• ... and 1 more: https://git.openjdk.org/jdk/compare/fd8089e571c098eb59036be7e7ae60cc54c4170c...master

Your commit was automatically rebased without conflicts.

[openjdk]

@dholmes-ora @dev-jonghoonpark Pushed as commit ec081d9.

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