8274130: C2: MulNode::Ideal chained transformations may act on wrong nodes

[shipilev]

I was puzzled by it when fixing JDK-8274060. It looks that new optimizations added by JDK-8273454 and JDK-8263006 rewire in(1) and in(2) in MulNode::Ideal, which means the chained transformations should see them? Yet, both inputs and their Type-s are cached locally and not refreshed. I have not seen failures due to this yet, but it looks that the current code is subtly incorrect because of this.

I thought about doing return this instead of progress = true, so that we leave MulNode::Ideal once we hit any transform and hope to return back, but I wondered if that would expose us to different graph shapes in-between successive MulNode::Ideal calls, which might have other unintended consequences. Therefore, I opted to a more conservative patch.

Additional testing:

• compiler/ tests
• tier1 tests
• 100K Fuzzer tests (one unrelated failure)

---

Progress

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Issue

• JDK-8274130: C2: MulNode::Ideal chained transformations may act on wrong nodes

Reviewers

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

Reviewing

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[mlbridge]

Webrevs

• 01: Full - Incremental (c8d3cb12)
• 00: Full (932f039a)

[adinn]

This is actually cleaner but I'm not sure the change is strictly needed. In these specific transforms I think the types of the operands and the operation ought never to differ.

e.g for the multuply rule we transform (MulF (MinusF f2) (MinusF f2)) ==> (MulF f1 f2. The types of the MinusF terms input to the MulF both have to be float. So, do the types of the inputs f1 and f2. We should never get an input graph that has, say, a float for one arg and a double for another.

[shipilev]

This is actually cleaner but I'm not sure the change is strictly needed. In these specific transforms I think the types of the operands and the operation ought never to differ.

For types and current transforms, that might be true. It might not hold true in future. The patch, however, also makes sure these lines refer to the most actual nodes:

        igvn->_worklist.push(in1);
        igvn->_worklist.push(in2);

[TobiHartmann]

That looks good to me (I would prefer the pointer asterisk next to the type though).

[shipilev]

That looks good to me (I would prefer the pointer asterisk next to the type though).

Aligned! See new commit.

[TobiHartmann]

Looks good, thanks for changing.

[openjdk]

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

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

8274130: C2: MulNode::Ideal chained transformations may act on wrong nodes

Reviewed-by: thartmann, kvn

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At the time when this comment was updated there had been 93 new commits pushed to the master branch:

• d8a278f: 8274396: Suppress more warnings on non-serializable non-transient instance fields in client libs
• e49e5b5: 8273972: Multi-core choke point in CMM engine (LCMSTransform.doTransform)
• 2072bc7: 8274391: Suppress more warnings on non-serializable non-transient instance fields in java.util.concurrent
• 6a477bd: 8274415: Suppress warnings on non-serializable non-transient instance fields in java.xml
• 67e52a3: 8273634: [TEST_BUG] Improve javax/swing/text/ParagraphView/6364882/bug6364882.java
• b7425b6: 8239502: [TEST_BUG] Test javax/swing/text/FlowView/6318524/bug6318524.java never fails
• c57a6c6: 8274265: Suspicious string concatenation in logTestUtils.inline.hpp
• 6f4cefb: 8274394: Use Optional.isEmpty instead of !Optional.isPresent in jdk.jlink
• 94f5e80: 8274276: Cache normalizedBase URL in URLClassPath.FileLoader
• b36881f: 8274383: JNI call of getAccessibleSelection on a wrong thread
• ... and 83 more: https://git.openjdk.java.net/jdk/compare/c77ebe88748b0a55f1fc7a5497314a752eab1e2a...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.

[shipilev]

Thanks!

/integrate

[openjdk]

Going to push as commit 756d22c.
Since your change was applied there have been 97 commits pushed to the master branch:

• 5b0c9cc: 8274172: Convert JavadocTester to use NIO
• 2657bcb: 8274136: -XX:+ExitOnOutOfMemoryError calls exit while threads are running
• 53b25bc: 8273459: Update code segment alignment to 64 bytes
• 1a29b1e: 8274016: Replace 'for' cycles with iterator with enhanced-for in java.desktop
• d8a278f: 8274396: Suppress more warnings on non-serializable non-transient instance fields in client libs
• e49e5b5: 8273972: Multi-core choke point in CMM engine (LCMSTransform.doTransform)
• 2072bc7: 8274391: Suppress more warnings on non-serializable non-transient instance fields in java.util.concurrent
• 6a477bd: 8274415: Suppress warnings on non-serializable non-transient instance fields in java.xml
• 67e52a3: 8273634: [TEST_BUG] Improve javax/swing/text/ParagraphView/6364882/bug6364882.java
• b7425b6: 8239502: [TEST_BUG] Test javax/swing/text/FlowView/6318524/bug6318524.java never fails
• ... and 87 more: https://git.openjdk.java.net/jdk/compare/c77ebe88748b0a55f1fc7a5497314a752eab1e2a...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 756d22c.

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