8342945: Replace predicate walking code in get_assertion_predicates() used for Loop Unswitching and cleaning useless Template Assertion Predicates with a predicate visitor

[chhagedorn]

Replacing the Remaining Predicate Walking and Cloning Code

The goal is to replace and unify all the remaining custom predicate walking and cloning code currently used for:

• JDK-8341977: Loop Peeling (integrated with 8341977: Replace predicate walking and cloning code for Loop Peeling with a predicate visitor #21679))
• JDK-8342943: Main and Post Loop (integrated with 8342943: Replace predicate walking and cloning code for main/post loops with a predicate visitor #21790)
• JDK-8342945: PhaseIdealLoop::get_assertion_predicates() used for Loop Unswitching and removing useless Template Assertion Predicate (this PR)
• JDK-8342946: Loop Unrolling (upcoming)

---

(Sections taken over from #21679 / #21790))

Single Template Assertion Predicate Check

This replacement allows us to have a single TemplateAssertionPredicate::is_predicate() check that is called for all predicate matching code. This enables the removal of uncommon traps for Template Assertion Predicates with JDK-8342047 which is a missing piece in order to fix the remaining problems with Assertion Predicates (JDK-8288981).

Common Refactorings for all the Patches in this Series

In each of the patch, I will do similar refactoring ideas:

• Replace the existing code in the corresponding PhaseIdealLoop method with call to a new (or existing) predicate visitor which extends the PredicateVisitor interface.
• The visitor implements the Assertion Predicate visit() methods to implement the cloning and initialization of the Template Assertion Predicates.
• The predicate visitor is then passed to the PredicateIterator which walks through all predicates found at a loop and applies the visitor for each predicate.
• The visitor creates new nodes (if there are Template Assertion Predicates) either in place or at the loop entry of a target loop. In the latter case, the calling code of the PredicateIterator must make sure to connect the tail of the newly created predicate chain after the old loop entry to the target loop head.
• Keep the semantics which includes to only apply the Template Assertion Predicate processing if there are Parse Predicates. This limitation should eventually be removed. But I want to do that separately at a later point.

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Refactorings of this Patch

• This patch replaces the predicate walking in PhaseIdealLoop::get_assertion_predicates() which is used for Loop Unswitching and removing useless Template Assertion Predicates (called from PhaseIdealLoop::collect_useful_template_assertion_predicates_for_loop()).
• Note that the cloning code in Loop Unswitching is not replaced, yet, because we clone the Template Assertion Predicates in the original order as currently found in the graph which also allowed us to use PhaseIdealLoop::create_new_if_for_predicate().
  This means that we first walk from the loop entry to the last Template Assertion Predicate and then start cloning them in the reverse order (which ensures that we keep the original order of the Template Assertion Predicates). I don't think that keeping the original order is a strong requirement.
  Once we replace the UCTs with halt nodes, we do not require to call create_new_if_for_predicate() anymore and could theoretically just clone and initialize the Template Assertion Predicates in the opposite order as originally found in the graph which is easier to implement. This is currently also done for the other loop opts that require Assertion Predicates cloning/initialization. I think it's probably safe to do this for Loop Unswitching as well once we replace UCTs with halt nodes (@rwestrel what do you think?).
  If at some point, we need to keep the Assertion Predicate order, we can just add this functionality to the PredicateIterator classes. Anyhow, I'm leaving this code inclone_assertion_predicates_to_unswitched_loop() as it is for now and revisit it later again.

Thanks,
Christian

---

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-8342945: Replace predicate walking code in get_assertion_predicates() used for Loop Unswitching and cleaning useless Template Assertion Predicates with a predicate visitor (Sub-task - P4)

Reviewers

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

Reviewing

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[bridgekeeper]

👋 Welcome back chagedorn! 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]

@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:

8342945: Replace predicate walking code in get_assertion_predicates() used for Loop Unswitching and cleaning useless Template Assertion Predicates with a predicate visitor

Reviewed-by: thartmann, roland, kvn

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At the time when this comment was updated there had been 9 new commits pushed to the master branch:

• c0e6c3b: 8343214: Fix encoding errors in APX New Data Destination Instructions Support
• 0be7118: 8279016: JFR Leak Profiler is broken with Shenandoah
• 6811a11: 8341408: Implement JEP 488: Primitive Types in Patterns, instanceof, and switch (Second Preview)
• 72a45dd: 8341834: C2 compilation fails with "bad AD file" due to Replicate
• 57c3bb6: 8343068: C2: CastX2P Ideal transformation not always applied
• 83f3d42: 8339303: C2: dead node after failing to match cloned address expression
• ead0116: 8331341: secondary_super_cache does not scale well: C1 and interpreter
• 06d8216: 8318442: java/net/httpclient/ManyRequests2.java fails intermittently on Linux
• bdd6816: 8343502: RISC-V: SIGBUS in updateBytesCRC32 after JDK-8339738

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
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[mlbridge]

Webrevs

• 00: Full (3d139c2b)

[TobiHartmann]

Looks good to me.

[chhagedorn]

Thanks Tobias for your review!

[rwestrel]

Looks good to me.

[chhagedorn]

Thanks Roland for your review!

[vnkozlov]

Looks good to me too.

[chhagedorn]

Thanks Vladimir for your review!

/integrate

[openjdk]

Going to push as commit a6c85da.
Since your change was applied there have been 16 commits pushed to the master branch:

• 97b681e: 8340586: JdkJfrEvent::get_all_klasses stores non-strong oops in JNI handles
• f2316f6: 8343505: Problemlist java/lang/Thread/jni/AttachCurrentThread/AttachTest.java
• 9e31e78: 8342647: [macosx] Clean up the NSInvocation based call to NSProcessInfo.operatingSystemVersion
• e33dc13: 8343343: Misc crash dump improvements on more platforms after JDK-8294160
• d20ccd1: 8335583: Avoid using pointers in CDS tables
• 342fe42: 8342270: Test sun/security/pkcs11/Provider/RequiredMechCheck.java needs write access to src tree
• 78b378a: 8342540: InterfaceCalls micro-benchmark gives misleading results
• c0e6c3b: 8343214: Fix encoding errors in APX New Data Destination Instructions Support
• 0be7118: 8279016: JFR Leak Profiler is broken with Shenandoah
• 6811a11: 8341408: Implement JEP 488: Primitive Types in Patterns, instanceof, and switch (Second Preview)
• ... and 6 more: https://git.openjdk.org/jdk/compare/4431852a880b06241231d346311170331c20ab2d...master

Your commit was automatically rebased without conflicts.

[openjdk]

@chhagedorn Pushed as commit a6c85da.

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