8291466: C2: assert(false) failed: infinite loop in PhaseIterGVN::transform_old with -XX:+StressIGVN

[pfustc]

Recently, an igvn infinite loop issue was reported. Git bisection shows it appears after our JDK-8289996 patch. But after that patch is backed out, we find similar test still fails. We have attached a jtreg case to reproduce this issue.

The ideal graph of the problematic method has a MulINode multiplying a PhiNode by a ConINode. For better optimizations, MulINode::Ideal() moves the constant input to the right hand side. And Ideal() function in its parent class MulNode has the similar logic. In some code paths, MulINode::Ideal() calls MulNode::Ideal(). The problem here is that, MulINode and MulNode use different ways to check constant. One calls type->singleton() and the other calls node->find_int_con(val) which accepts constant in PhiNode. So in some corner cases where a PhiNode can be evaluated to a constant, the two inputs of the MulNode will be swapped back and forth in Ideal() calls. It eventually causes the igvn infinite loop issue.

This patch removes the swap_edges() logic in MulINode and MulLNode because it's enough to do this by calling MulNode::Ideal(). We also do some code cleanup in this patch as we have done in JDK-8289996.

Tested hotspot::hotspot_all_no_apps, jdk::tier1~3 and langtools::tier1.

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Issue

• JDK-8291466: C2: assert(false) failed: infinite loop in PhaseIterGVN::transform_old with -XX:+StressIGVN

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[bridgekeeper[bot]]

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[openjdk[bot]]

@pfustc The following label will be automatically applied to this pull request:

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[pfustc]

/cc hotspot-compiler

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@pfustc The hotspot-compiler label was successfully added.

[mlbridge[bot]]

Webrevs

• 03: Full (aa609c3d)
• 02: Full - Incremental (1e455e31)
• 01: Full - Incremental (7272ce10)
• 00: Full (8ca74190)

[pfustc]

PING. Any reviewer can help look at this? @shipilev

[openjdk[bot]]

@pfustc 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:

8291466: C2: assert(false) failed: infinite loop in PhaseIterGVN::transform_old with -XX:+StressIGVN

Reviewed-by: roland, chagedorn

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

• d5167a91a9d35afba1a2f246f9d320f1cbb998b2: 7189422: [macosx] Submenu's arrow have a wrong position

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

@pfustc this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout igvn
git fetch https://git.openjdk.org/jdk master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[pfustc]

@chhagedorn Thanks for your review. Currently this patch has conflicts with jdk master. I will try a merge and then do the minor fixes as you suggested.

[pfustc]

/integrate

[openjdk[bot]]

Going to push as commit a88a9e344f66bca21f3a01dbbcea19b52af14865. Since your change was applied there has been 1 commit pushed to the master branch:

• d5167a91a9d35afba1a2f246f9d320f1cbb998b2: 7189422: [macosx] Submenu's arrow have a wrong position

Your commit was automatically rebased without conflicts.

[openjdk[bot]]

@pfustc Pushed as commit a88a9e344f66bca21f3a01dbbcea19b52af14865.

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