8370441: Remove unnecessary/confusing null check in Verifier::verify()

[Arraying]

JDK-8059924 introduced a nullcheck for a klass' Java mirror which runs during verification. However, in the modern VM, during verification time, the mirror is guaranteed to exist making the check unnecessary and misleading when reading the code. While implementing JDK-8366488 it caused for quite some confusion. With this PR it is my intention to make sure that nobody gets side-tracked by this impossible condition.

For an insight into previous discussion on this topic, please see the associated JBS issue.

Testing: tiers 1-5 on Linux x64, AArch64, macOS x64, AArch64, Windows x64.

---

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

Issue

• JDK-8370441: Remove unnecessary/confusing null check in Verifier::verify() (Enhancement - P4)

Reviewers

• David Holmes (@dholmes-ora - Reviewer)
• Coleen Phillimore (@coleenp - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/29314/head:pull/29314
$ git checkout pull/29314

Update a local copy of the PR:
$ git checkout pull/29314
$ git pull https://git.openjdk.org/jdk.git pull/29314/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 29314

View PR using the GUI difftool:
$ git pr show -t 29314

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/29314.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back phubner! 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]

@Arraying 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:

8370441: Remove unnecessary/confusing null check in Verifier::verify()

Reviewed-by: dholmes, coleenp

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 201 new commits pushed to the master branch:

• 176422b: 8370519: C2: Hit MemLimit when running with +VerifyLoopOptimizations
• 17f25b5: 8375536: PPC64: Implement special MachNodes for floating point CMove
• e370b8a: 8376570: GrowableArray::remove_{till,range} should work on empty list
• ... and 198 more: https://git.openjdk.org/jdk/compare/d9db4fb36e4f90546dc3fc19b5923b8be6a2f518...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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@dholmes-ora, @coleenp) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[openjdk]

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

• hotspot-runtime

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 01: Full - Incremental (1ecae607)
• 00: Full (78fa2983)

[dholmes-ora]

Looks good.

The analysis seems correct and I agree that checking for impossible conditions is confusing.

Thanks

[coleenp]

Looks good!

[Arraying]

Thanks for the reviews!
/integrate

[openjdk]

@Arraying
Your change (at version 1ecae60) is now ready to be sponsored by a Committer.

[dholmes-ora]

/sponsor

[openjdk]

Going to push as commit e21cb85.
Since your change was applied there have been 213 commits pushed to the master branch:

• caf1338: 8376700: java/nio/file/DirectoryStream/SecureDS.java fails AtomicMoveNotSupportedException
• 1cb4ef8: 8376855: ASAN reports out-of-range read in strncmp in MethodHandles::is_basic_type_signature
• 67079b1: 8377000: [BACKOUT] JDK-8376126 G1: Convert remaining volatiles in G1ConcurrentMark to Atomic
• ... and 210 more: https://git.openjdk.org/jdk/compare/d9db4fb36e4f90546dc3fc19b5923b8be6a2f518...master

Your commit was automatically rebased without conflicts.

[openjdk]

@dholmes-ora @Arraying Pushed as commit e21cb85.

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

[dholmes-ora]

Since your change was applied there have been 213 commits pushed to the master branch:

@Arraying please merge with master before integrating if your PR gets a long way behind the master branch. Thanks