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8260370: C2: LoopLimit node is not eliminated #134

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@iwanowww iwanowww commented Jan 26, 2021

As part of JDK-8255000 C->major_progress check was replaced with an explicit phase check (post_loop_opts_phase()).
But LoopLimit was not covered and still relied on C->major_progress(). It exposed a problem: sometimes IGVN sets major_progress (e.g., see LoopNode::Ideal()) and it blocks LoopLimit node elimination if the node is processed later (LoopLimitNode::Ideal() is misled that loop opts phase is not over).

The fix migrates LoopLimitNode::Ideal() to post_loop_opts_phase().

Also, post-loop opts IGVN pass conservatively clears major_progress() just in case.

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  • failing test
  • hs-tier1 - hs-tier4

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$ git fetch https://git.openjdk.java.net/jdk16 pull/134/head:pull/134
$ git checkout pull/134

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bridgekeeper bot commented Jan 26, 2021

👋 Welcome back vlivanov! 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.

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openjdk bot commented Jan 26, 2021

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

  • hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

@openjdk openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.java.net label Jan 26, 2021
@iwanowww iwanowww marked this pull request as ready for review January 26, 2021 17:14
@openjdk openjdk bot added the rfr Pull request is ready for review label Jan 26, 2021
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mlbridge bot commented Jan 26, 2021

Webrevs

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@vnkozlov vnkozlov left a comment

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Looks good.
Do we have other places where we should replace major_progress()?

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openjdk bot commented Jan 26, 2021

@iwanowww 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:

8260370: C2: LoopLimit node is not eliminated

Reviewed-by: kvn, thartmann

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

  • 408772c: 8259025: Record compact constructor using Objects.requireNonNull

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@openjdk openjdk bot added the ready Pull request is ready to be integrated label Jan 26, 2021
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Thanks for the prompt review, Vladimir.

Do we have other places where we should replace major_progress()?

Yes, there's at least one check left (in SafePointNode::Identity). I plan to address it separately.

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Looks good to me.

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/integrate

@openjdk openjdk bot closed this Jan 27, 2021
@openjdk openjdk bot added integrated Pull request has been integrated and removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jan 27, 2021
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openjdk bot commented Jan 27, 2021

@iwanowww Since your change was applied there has been 1 commit pushed to the master branch:

  • 408772c: 8259025: Record compact constructor using Objects.requireNonNull

Your commit was automatically rebased without conflicts.

Pushed as commit e28e111.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

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