8297951: C2: Create skeleton predicates for all If nodes in loop predication

[chhagedorn]

We currently only create skeleton predicates for RangeCheck nodes and not for normal If nodes:

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

Lines 1344 to 1346 in 2cb64a7

	if (iff->is_RangeCheck()) {
	new_predicate_proj = insert_initial_skeleton_predicate(iff, loop, proj, predicate_proj, upper_bound_proj, scale, offset, init, limit, stride, rng, overflow, reason);
	}

But it is also possible to create range check predicates in loop predication for If nodes if they have the right pattern checked in PhaseIdealLoop::loop_predication_impl() and IdealLoopTree::is_range_check_if(). This, however, is much more rare.

Without skeleton predicates for these If nodes, we could run into the same problems already fixed for RangeCheck nodes (see JDK-8193130 and related bugs). This is almost impossible to trigger in practice as it needs a very specific setup and the right optimizations to be applied. But the test case shows such a case where we hit an assert due to a broken memory graph because we are missing skeleton predicates.

I therefore propose to always create skeleton predicates for hoisted range checks in loop predication.

Thanks,
Christian

---

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Issue

• JDK-8297951: C2: Create skeleton predicates for all If nodes in loop predication

Reviewers

• Tobias Hartmann (@TobiHartmann - Reviewer)
• Vladimir Kozlov (@vnkozlov - Reviewer)

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[mlbridge]

Webrevs

• 00: Full (19ad5f07)

[TobiHartmann]

Looks reasonable to me. Great that you were able to find a test!

[openjdk]

@chhagedorn This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8297951: C2: Create skeleton predicates for all If nodes in loop predication

Reviewed-by: thartmann, kvn

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At the time when this comment was updated there had been 240 new commits pushed to the master branch:

• 7d20a60: 8297489: Modify TextAreaTextEventTest.java as to verify the content change of TextComponent sends TextEvent
• 601264d: 8273357: SecurityManager deprecation warning from java/awt/regtesthelpers/Util.java
• 6a7a0db: 8296619: Upgrade jQuery to 3.6.1
• a38c63d: 8297733: Refactor Cast binding to enum
• 19d8498: 8297495: j.u.concurrent updates for JDK 20
• 3288459: 8297606: [AIX] Broken build after JDK-8295475
• 0452c39: 8296477: Foreign linker implementation update following JEP 434
• 73baadc: 8295044: Implementation of Foreign Function and Memory API (Second Preview)
• bd38188: 8297766: Remove UseMallocOnly development option
• b9eec96: 8281214: Unsafe use of long in VMThread::setup_periodic_safepoint_if_needed
• ... and 230 more: https://git.openjdk.org/jdk/compare/bcc6b12b711a9c5007d963123fb38a7e72aaf8e5...master

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[chhagedorn]

Thanks Tobias for your review!

[vnkozlov]

Make sense.

[chhagedorn]

Thank you Vladimir for your review!

[chhagedorn]

/integrate

[openjdk]

Going to push as commit 0bd04a6.
Since your change was applied there have been 250 commits pushed to the master branch:

• f5ad515: 8297247: Add GarbageCollectorMXBean for Remark and Cleanup pause time in G1
• e975418: 8298102: Remove DirtyCardToOopClosure::_last_explicit_min_done
• 04012c4: 8298111: Cleanups after UseMallocOnly removal
• ee9ba74: 8295184: Printing messages with a RecordComponentElement does not include position
• ba2d28e: 8298027: Remove SCCS id's from awt jtreg tests
• 8d8a28f: 8296489: tools/jpackage/windows/WinL10nTest.java fails with timeout
• 884b9ad: 8293453: tools/jpackage/share/AddLShortcutTest.java "Failed: Check the number of mismatched pixels [1024] of [1024] is < [0.100000] threshold"
• 8af6e8a: 8298123: Problem List MaximizedToIconified.java on macOS
• da0917a: 8297729: Replace GrowableArray in ComputeMoveOrder with hash table
• 9827b75: 8298043: jdk/jfr/api/consumer/recordingstream/TestStop.java failed with "Expected outer stream to have 3 events"
• ... and 240 more: https://git.openjdk.org/jdk/compare/bcc6b12b711a9c5007d963123fb38a7e72aaf8e5...master

Your commit was automatically rebased without conflicts.

[openjdk]

@chhagedorn Pushed as commit 0bd04a6.

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