8345269: Fix -Wzero-as-null-pointer-constant warnings in ppc code

[kimbarrett]

Please review this change to remove -Wzero-as-null-pointer-constant warnings
in ppc code.

Most places involve just changing literal 0 to nullptr.

Removed a dead return after ShouldNotReachHere() that is no longer needed.

Removed some unused Address constructors that had a default address argument
with literal 0 as the default value. These could have been changed to use
nullptr as the default value, but since they aren't used...

Testing:
GHA sanity test build, with and without -Wzero-as-null-pointer-constant enabled.
I don't have the capability to run tests for this platform, so hoping someone
from the aix-ppc maintainers can do more testing.

---

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-8345269: Fix -Wzero-as-null-pointer-constant warnings in ppc code (Enhancement - P4)

Reviewers

• Martin Doerr (@TheRealMDoerr - Reviewer)
• Matthias Baesken (@MBaesken - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/22466/head:pull/22466
$ git checkout pull/22466

Update a local copy of the PR:
$ git checkout pull/22466
$ git pull https://git.openjdk.org/jdk.git pull/22466/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 22466

View PR using the GUI difftool:
$ git pr show -t 22466

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/22466.diff

Using 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:

8345269: Fix -Wzero-as-null-pointer-constant warnings in ppc code

Reviewed-by: mdoerr, mbaesken

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 27 new commits pushed to the master branch:

• cf0e1aa: 8345335: Add excluded jdk_foreign tests to manual group
• 2c4567a: 8342651: Refactor array constant to use an array of jbyte
• 72c6daf: 8346007: Incorrect copyright header in UModLNodeIdealizationTests.java
• cc47918: 8345040: Clean up unused variables and code in generate_native_wrapper
• c34b87c: 8345659: Fix broken alignment after ReservedSpace splitting in GC code
• e294899: 8345647: Fix recent NULL usage backsliding in Shenandoah
• d381d58: 8332268: C2: Add missing optimizations for UDivI/L and UModI/L and unify the shared logic with the signed nodes
• 45c914c: 8343607: C2: Shenandoah crashes during barrier expansion in Continuation::enter
• a21d21f: 8345609: [C1] LIR Operations with one input should be implemented as LIR_Op1
• 2382a2d: 8345661: Simplify page size alignment in code heap reservation
• ... and 17 more: https://git.openjdk.org/jdk/compare/d6b5264c3f7d0c4157ebd73b2f1a98dd15273c61...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]

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[mlbridge]

Webrevs

• 02: Full - Incremental (2a35f20d)
• 01: Full - Incremental (a3941e41)
• 00: Full (31047fc7)

[kimbarrett]

Anyone? Especially somebody from the aix-ppc folks?

[TheRealMDoerr]

Thanks for fixing it! LGTM.

[kimbarrett]

Thanks for reviews @MBaesken and @TheRealMDoerr

[kimbarrett]

/integrate

[openjdk]

Going to push as commit 08bdeed.
Since your change was applied there have been 29 commits pushed to the master branch:

• e4a34e9: 8345616: Unnecessary Hashtable usage in javax.swing.text.html.parser.Element
• cce5808: 8345421: (bf) Create specific test for temporary direct buffers and the buffer size limit
• cf0e1aa: 8345335: Add excluded jdk_foreign tests to manual group
• 2c4567a: 8342651: Refactor array constant to use an array of jbyte
• 72c6daf: 8346007: Incorrect copyright header in UModLNodeIdealizationTests.java
• cc47918: 8345040: Clean up unused variables and code in generate_native_wrapper
• c34b87c: 8345659: Fix broken alignment after ReservedSpace splitting in GC code
• e294899: 8345647: Fix recent NULL usage backsliding in Shenandoah
• d381d58: 8332268: C2: Add missing optimizations for UDivI/L and UModI/L and unify the shared logic with the signed nodes
• 45c914c: 8343607: C2: Shenandoah crashes during barrier expansion in Continuation::enter
• ... and 19 more: https://git.openjdk.org/jdk/compare/d6b5264c3f7d0c4157ebd73b2f1a98dd15273c61...master

Your commit was automatically rebased without conflicts.

[openjdk]

@kimbarrett Pushed as commit 08bdeed.

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