8336297: C2: Fix -Wzero-as-null-pointer-constant warnings in derived Node ctors

[kimbarrett]

Please review this change that removes some -Wzero-as-null-pointer-constant
warnings (when enabled) in C2 code. The constructors for some classes derived
from Node pass 0 as the first argument to the base class constructor. Since
that parameter is a Node*, this triggers a warning. Changing to pass nullptr
removes the warning.

Testing: mach5 tier1

---

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-8336297: C2: Fix -Wzero-as-null-pointer-constant warnings in derived Node ctors (Enhancement - P4)

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer)
• Julian Waters (@TheShermanTanker - Committer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/20162/head:pull/20162
$ git checkout pull/20162

Update a local copy of the PR:
$ git checkout pull/20162
$ git pull https://git.openjdk.org/jdk.git pull/20162/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 20162

View PR using the GUI difftool:
$ git pr show -t 20162

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/20162.diff

Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back kbarrett! 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]

@kimbarrett 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:

8336297: C2: Fix -Wzero-as-null-pointer-constant warnings in derived Node ctors

Reviewed-by: kvn, jwaters

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 15 new commits pushed to the master branch:

• 3f2636d: 8335820: java/lang/invoke/LFCaching/LFSingleThreadCachingTest.java fails due to IllegalArgumentException: hash must be nonzero
• a9f5e76: 8335905: CompoundElement API cleanup
• 6f325db: 8310915: Typo in aarch64.ad: "envcodings"
• ae9f318: 8336301: test/jdk/java/nio/channels/AsyncCloseAndInterrupt.java leaves around a FIFO file upon test completion
• 4166e53: 8318106: Generated HTML for snippet does not always contain an id
• 5bc86f3: 8336259: Wrong link to stylesheet.css in JavaDoc API documentation
• 8ba9bc6: 8332249: Micro-optimize Method.hashCode
• 4957145: 8336278: Micro-optimize Replace String.format("%n") to System.lineSeparator
• 1f6e106: 8335684: Test ThreadCpuTime.java should pause like ThreadCpuTimeArray.java
• 84c74ad: 8335802: Improve startup speed HexFormat uses boolean instead of enum
• ... and 5 more: https://git.openjdk.org/jdk/compare/9b6f6c5c9dd6d0fbb056e8d84c3a0888a3320edf...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.

[openjdk]

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

• graal
• hotspot-compiler

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

[mlbridge]

Webrevs

• 00: Full (97c3acfb)

[vnkozlov]

Good.

[kimbarrett]

Thanks for reviews @vnkozlov and @TheShermanTanker

[kimbarrett]

/integrate

[openjdk]

Going to push as commit ab27aca.
Since your change was applied there have been 21 commits pushed to the master branch:

• 9dfcd75: 8334121: Anonymous class capturing two enclosing instances fails to compile
• 000de30: 8335269: [Graal] occasional timeout in java/lang/StringBuffer/TestSynchronization.java with loom
• 4635531: 8335159: Move method reference to lambda desugaring before Lower
• a253e0f: 8335642: Hide Transform implementation for Class-File API
• 2b0adfc: 8335817: javac AssertionError addLocalVar checkNull
• a96de6d: 8336256: memcpy short value to int local is incorrect in VtableStubs::unsafe_hash
• 3f2636d: 8335820: java/lang/invoke/LFCaching/LFSingleThreadCachingTest.java fails due to IllegalArgumentException: hash must be nonzero
• a9f5e76: 8335905: CompoundElement API cleanup
• 6f325db: 8310915: Typo in aarch64.ad: "envcodings"
• ae9f318: 8336301: test/jdk/java/nio/channels/AsyncCloseAndInterrupt.java leaves around a FIFO file upon test completion
• ... and 11 more: https://git.openjdk.org/jdk/compare/9b6f6c5c9dd6d0fbb056e8d84c3a0888a3320edf...master

Your commit was automatically rebased without conflicts.

[openjdk]

@kimbarrett Pushed as commit ab27aca.

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