8376104: C2 crashes in PhiNode::Ideal(PhaseGVN*, bool) accessing NULL pointer

[wkia]

Backporting JDK-8376104 C2 crashes in PhiNode::Ideal(PhaseGVN*, bool) accessing NULL pointer

This PR backports the fix for C2 segmentation fault that occurs on nullptr dereferencing when the call to MemNode::optimize_memory_chain within PhiNode::Ideal can kill the Phi node itself.

make test TEST=hotspot_compiler is OK.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8376104 needs maintainer approval

Issue

• JDK-8376104: C2 crashes in PhiNode::Ideal(PhaseGVN*, bool) accessing NULL pointer (Bug - P3)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/383/head:pull/383
$ git checkout pull/383

Update a local copy of the PR:
$ git checkout pull/383
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/383/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 383

View PR using the GUI difftool:
$ git pr show -t 383

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/383.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back rmarchenko! 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]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[mlbridge]

Webrevs

• 01: Full - Incremental (331c5eae)
• 00: Full (a537d171)

[openjdk]

@wkia Please do not rebase or force-push to an active PR as it invalidates existing review comments. Note for future reference, the bots always squash all changes into a single commit automatically as part of the integration. See OpenJDK Developers’ Guide for more information.

[openjdk]

@wkia Please do not rebase or force-push to an active PR as it invalidates existing review comments. Note for future reference, the bots always squash all changes into a single commit automatically as part of the integration. See OpenJDK Developers’ Guide for more information.

[openjdk]

⚠️ @wkia This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.