8316361: C2: assert(!failure) failed: Missed optimization opportunity in PhaseIterGVN with -XX:VerifyIterativeGVN=10

[eme64]

This seems to be related to JDK-8298176 / openjdk/jdk20#65
This change allows OpaqueZeroTripGuard -> CmpI to fold in some cases. We have also added code to notify the CmpI during IGVN, so it can potentially change its type/constant fold:

jdk/src/hotspot/share/opto/phaseX.cpp

Lines 1681 to 1687 in a0a09d5

	if (use->Opcode() == Op_OpaqueZeroTripGuard) {
	assert(use->outcnt() <= 1, "OpaqueZeroTripGuard can't be shared");
	if (use->outcnt() == 1) {
	Node* cmp = use->unique_out();
	_worklist.push(cmp);
	}
	}

However, when we hack the input to the opaq node, we must call _igvn.add_users_to_worklist to trigger this notification. I added this missing part.

Running Tier1-6 and stress testing... passed.

---

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Issue

• JDK-8316361: C2: assert(!failure) failed: Missed optimization opportunity in PhaseIterGVN with -XX:VerifyIterativeGVN=10 (Bug - P4)

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer)
• Christian Hagedorn (@chhagedorn - Reviewer)

Reviewing

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• 00: Full (c7b7c0a3)

[vnkozlov]

Good.

[openjdk]

@eme64 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:

8316361: C2: assert(!failure) failed: Missed optimization opportunity in PhaseIterGVN with -XX:VerifyIterativeGVN=10

Reviewed-by: kvn, chagedorn

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 111 new commits pushed to the master branch:

• 6948942: 8317327: Remove JT_JAVA dead code in jib-profiles.js
• 795e5dc: 8315503: G1: Code root scan causes long GC pauses due to imbalanced iteration
• 207819a: 8315604: IGV: dump and visualize node bottom and phase types
• 8fcf70e: 5066247: Refine the spec of equals() and hashCode() for j.text.Format classes
• 93f662f: 8317335: Build on windows fails after 8316645
• b8fa6c2: 8316186: RISC-V: Remove PlatformCmpxchg<4>
• fb055e7: 8316645: RISC-V: Remove dependency on libatomic by adding cmpxchg 1b
• 009f5e1: 8317141: Remove unused validIndex method from URLClassPath$JarLoader
• 47569a2: 8295919: java.security.MessageDigest.isEqual does not adhere to @implNote
• 5a6aa56: 8303959: tools/jpackage/share/RuntimePackageTest.java fails with java.lang.AssertionError missing files
• ... and 101 more: https://git.openjdk.org/jdk/compare/fe862639e7ce40f5adef0e482b1fb9c718e061a3...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.

[chhagedorn]

Looks good!

[eme64]

Thanks for the reviews @vnkozlov @chhagedorn !
/integrate

[openjdk]

Going to push as commit eeb63cd.
Since your change was applied there have been 111 commits pushed to the master branch:

• 6948942: 8317327: Remove JT_JAVA dead code in jib-profiles.js
• 795e5dc: 8315503: G1: Code root scan causes long GC pauses due to imbalanced iteration
• 207819a: 8315604: IGV: dump and visualize node bottom and phase types
• 8fcf70e: 5066247: Refine the spec of equals() and hashCode() for j.text.Format classes
• 93f662f: 8317335: Build on windows fails after 8316645
• b8fa6c2: 8316186: RISC-V: Remove PlatformCmpxchg<4>
• fb055e7: 8316645: RISC-V: Remove dependency on libatomic by adding cmpxchg 1b
• 009f5e1: 8317141: Remove unused validIndex method from URLClassPath$JarLoader
• 47569a2: 8295919: java.security.MessageDigest.isEqual does not adhere to @implNote
• 5a6aa56: 8303959: tools/jpackage/share/RuntimePackageTest.java fails with java.lang.AssertionError missing files
• ... and 101 more: https://git.openjdk.org/jdk/compare/fe862639e7ce40f5adef0e482b1fb9c718e061a3...master

Your commit was automatically rebased without conflicts.

[openjdk]

@eme64 Pushed as commit eeb63cd.

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