8314106: C2: assert(is_valid()) failed: must be valid after JDK-8305636

[chhagedorn]

In the failing test case, we are unswitching a loop for which we've already removed Parse Predicates with Compile::cleanup_parse_predicates(). We are wrongly checking if a predicate block is non-empty (i.e. find the Parse or Runtime Predicates) instead of only checking if we find the Parse Predicate:

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

Lines 448 to 453 in 23fe2ec

	if (predicate_block->is_non_empty()) {
	clone_parse_predicate_to_unswitched_loops(predicate_block, reason, iffast_pred, ifslow_pred);
	clone_assertion_predicates_to_unswitched_loop(loop, old_new, reason, predicate_block->parse_predicate_success_proj(),
	iffast_pred, ifslow_pred);
	}

In the test case, we have a predicate block that contains Runtime Predicates from Loop Predication but no Parse Predicate anymore. Therefore, when trying to clone the non-existing Parse Predicate, we fail with the assertion because we do not have a valid Parse Predicate.

The fix is to only clone a Parse Predicate and the Assertion Predicates for a predicate block if the Parse Predicate is actually there. This is not entirely correct because we would also need to clone Assertion Predicates in the absence of Parse Predicates. But this was already wrong before JDK-8305636:

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

Lines 598 to 612 in a38fdaf

	ParsePredicates parse_predicates(entry);
	ParsePredicateSuccessProj* loop_predicate_proj = parse_predicates.loop_predicate_proj();
	if (loop_predicate_proj != nullptr) {
	// Clone Parse Predicate and Template Assertion Predicates of the Loop Predicate Block.
	iffast_pred = clone_parse_predicate_to_unswitched_loop(loop_predicate_proj, iffast_pred,
	Deoptimization::Reason_predicate, false);
	check_cloned_parse_predicate_for_unswitching(iffast_pred, true);
	ifslow_pred = clone_parse_predicate_to_unswitched_loop(loop_predicate_proj, ifslow_pred,
	Deoptimization::Reason_predicate, true);
	check_cloned_parse_predicate_for_unswitching(ifslow_pred, false);
	clone_assertion_predicates_to_unswitched_loop(loop, old_new, Deoptimization::Reason_predicate, loop_predicate_proj,
	iffast_pred, ifslow_pred);
	}

This will only be fixed with the complete fix (JDK-8288981). The proposed fix here just reverts back to the old behavior before JDK-8305636.

Thanks,
Christian

---

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Issue

• JDK-8314106: C2: assert(is_valid()) failed: must be valid after JDK-8305636 (Bug - P3)

Reviewers

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

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[TobiHartmann]

Looks good and trivial to me.

[openjdk]

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

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8314106: C2: assert(is_valid()) failed: must be valid after JDK-8305636

Reviewed-by: thartmann, kvn

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At the time when this comment was updated there had been 56 new commits pushed to the master branch:

• bd1b942: 8313905: Checked_cast assert in CDS compare_by_loader
• 9b53251: 8313654: Test WaitNotifySuspendedVThreadTest.java timed out
• e7c83ea: 8312194: test/hotspot/jtreg/applications/ctw/modules/jdk_crypto_ec.java cannot handle empty modules
• 23fe2ec: 8313616: support loading library members on AIX in os::dll_load
• f47767f: 8313882: Fix -Wconversion warnings in runtime code
• 0cb9ab0: 8313239: InetAddress.getCanonicalHostName may return ip address if reverse lookup fails
• 028b3ae: 8313874: JNI NewWeakGlobalRef throws exception for null arg
• 83adaf5: 8313421: [JVMCI] avoid locking class loader in CompilerToVM.lookupType
• 35b60f9: 8298095: Refine implSpec for SegmentAllocator
• 6dba202: 8313670: Simplify shared lib name handling code in some tests
• ... and 46 more: https://git.openjdk.org/jdk/compare/dc01604756c22889412f9f25b534488180327317...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.

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[vnkozlov]

Good.

[chhagedorn]

Thanks Tobias and Vladimir for your reviews!

[chhagedorn]

/integrate

[openjdk]

Going to push as commit 1de5bf1.
Since your change was applied there have been 73 commits pushed to the master branch:

• 5c91622: 8314117: RISC-V: Incorrect VMReg encoding in RISCV64Frame.java
• 6bbcef5: 8313948: Remove unnecessary static fields defaultUpper/defaultLower in sun.net.PortConfig
• b88c273: 8313743: Make fields final in sun.nio.ch
• ec0cc63: 8313904: [macos] All signing tests which verifies unsigned app images are failing
• 7332502: 8314139: TEST_BUG: runtime/os/THPsInThreadStackPreventionTest.java could fail on machine with large number of cores
• 8f1c134: 8313798: [aarch64] sun/tools/jhsdb/HeapDumpTestWithActiveProcess.java sometimes times out on aarch64
• 1232677: 8313244: NM flags handling in configure process
• 6ffc032: 8314113: G1: Remove unused G1CardSetInlinePtr::card_at
• 62adeb0: 8311648: Refactor the Arena/Chunk/ChunkPool interface
• 43462a3: 8313224: Avoid calling JavaThread::current() in MemAllocator::Allocation constructor
• ... and 63 more: https://git.openjdk.org/jdk/compare/dc01604756c22889412f9f25b534488180327317...master

Your commit was automatically rebased without conflicts.

[openjdk]

@chhagedorn Pushed as commit 1de5bf1.

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