8326638: Crash in PhaseIdealLoop::remix_address_expressions due to unexpected Region instead of Loop #18002

TobiHartmann · 2024-02-26T08:33:26Z

Adds a missing _head->is_Loop() check to handle the case when the loop head is not a LoopNode but a RegionNode because the loop is irreducible:

(rr) p n_loop->_head->dump(1)
  412 IfTrue === 411 [[ 345 ]] #1 !jvms: Test$Class1::Class1_method0 @ bci:286 (line 119)
  339 SafePoint === 336 1 340 1 1 344 290 1 1 1 1 291 1 1 293 294 295 1 320 297 1 298 299 300 301 302 1 303 1 [[ 345 ]] SafePoint !jvms: Test$Class1::Class1_method0 @ bci:307 (line 122)
  345 Region === 345 339 412 [[ 345 456 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 1861 1863 1865 1867 1882 1888 ]] #irreducible !jvms: Test$Class1::Class1_method0 @ bci:138 (line 101)

We then crash when invoking LoopNode::skip_strip_mined on a RegionNode or assert in debug. Unfortunately, I was not able to simply the test any further.

This is a regression from JDK-8303511 in JDK 21 b13

Thanks,
Tobias

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Issue

JDK-8326638: Crash in PhaseIdealLoop::remix_address_expressions due to unexpected Region instead of Loop (Bug - P3)

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Christian Hagedorn (@chhagedorn - Reviewer)
Vladimir Kozlov (@vnkozlov - Reviewer)

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…expected Region instead of Loop

bridgekeeper · 2024-02-26T08:34:20Z

👋 Welcome back thartmann! 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 · 2024-02-26T08:35:27Z

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

hotspot-compiler

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mlbridge · 2024-02-26T08:40:04Z

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01: Full - Incremental (12d59c1d)
00: Full (a6559cee)

chhagedorn

Otherwise, looks good!

chhagedorn · 2024-02-26T09:07:54Z

src/hotspot/share/opto/loopopts.cpp

@@ -583,7 +583,9 @@ Node* PhaseIdealLoop::remix_address_expressions(Node* n) {
            n23_loop == n_loop) {
          Node* add1 = new AddPNode(n->in(1), n->in(2)->in(2), n->in(3));
          // Stuff new AddP in the loop preheader
-          register_new_node(add1, n_loop->_head->as_Loop()->skip_strip_mined(1)->in(LoopNode::EntryControl));
+          Node* entry = n_loop->_head->is_Loop() ? n_loop->_head->as_Loop()->skip_strip_mined(1)->in(LoopNode::EntryControl)


Should we add a sanity assert (which could also serve as an explaining comment) that in the RegionNode case, it must be an irreducible loop head?

I could do that but it would feel a bit arbitrary to put the assert only in this code, given that we have the same is_Loop check in a lot of other code as well. Maybe it would make sense to factor the checks into a separate method at some point.

Makes sense to do a complete replacement of this pattern in other code as well at some point. But let's do that separately.

I agree with refactoring in separate RFE.

Regarding these changes: should we simply skip this optimization if we see irreducible loop? They may have additional entry into the body so such transformation could be incorrect.

Right, let's better be safe than sorry and skip this optimization for irreducible loops. The other optimizations in that method look safe though.

openjdk · 2024-02-26T09:09:34Z

@TobiHartmann 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:

8326638: Crash in PhaseIdealLoop::remix_address_expressions due to unexpected Region instead of Loop

Reviewed-by: chagedorn, kvn

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 35 new commits pushed to the master branch:

81b065a: 8326714: Make file-local functions static in src/java.base/unix/native/libjava/childproc.c
4fcae1a: 8326722: Cleanup unnecessary forward declaration in collectedHeap.hpp
c5c866a: 8326219: applications/kitchensink/Kitchensink8H.java timed out
ac3ce2a: 8326583: Remove over-generalized DefineNativeToolchain solution
bceaed6: 8326406: Remove mapfile support from makefiles
16d917a: 8313710: jcmd: typo in the documentation of JFR.start and JFR.dump
60cbf29: 8325754: Dead AbstractQueuedSynchronizer$ConditionNodes survive minor garbage collections
da14aa4: 8017234: Hotspot should stop using mapfiles
d482c1a: 8326524: Rename agent_common.h
e85355a: 8320005: Allow loading of shared objects with .a extension on AIX
... and 25 more: https://git.openjdk.org/jdk/compare/09f755a64db2e38d59c89e6b14d6e409f51126e4...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

vnkozlov

Good.

TobiHartmann · 2024-02-27T16:55:45Z

Thanks for the reviews, Vladimir and Christian.

TobiHartmann · 2024-02-27T16:57:34Z

/integrate

openjdk · 2024-02-27T16:58:24Z

Going to push as commit 9f0e7da.
Since your change was applied there have been 35 commits pushed to the master branch:

81b065a: 8326714: Make file-local functions static in src/java.base/unix/native/libjava/childproc.c
4fcae1a: 8326722: Cleanup unnecessary forward declaration in collectedHeap.hpp
c5c866a: 8326219: applications/kitchensink/Kitchensink8H.java timed out
ac3ce2a: 8326583: Remove over-generalized DefineNativeToolchain solution
bceaed6: 8326406: Remove mapfile support from makefiles
16d917a: 8313710: jcmd: typo in the documentation of JFR.start and JFR.dump
60cbf29: 8325754: Dead AbstractQueuedSynchronizer$ConditionNodes survive minor garbage collections
da14aa4: 8017234: Hotspot should stop using mapfiles
d482c1a: 8326524: Rename agent_common.h
e85355a: 8320005: Allow loading of shared objects with .a extension on AIX
... and 25 more: https://git.openjdk.org/jdk/compare/09f755a64db2e38d59c89e6b14d6e409f51126e4...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-02-27T16:58:31Z

@TobiHartmann Pushed as commit 9f0e7da.

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

TobiHartmann · 2024-02-28T06:28:33Z

/backport jdk22u

openjdk · 2024-02-28T06:29:41Z

@TobiHartmann the backport was successfully created on the branch backport-TobiHartmann-9f0e7da6 in my personal fork of openjdk/jdk22u. To create a pull request with this backport targeting openjdk/jdk22u:master, just click the following link:

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Hi all,

This pull request contains a backport of commit 9f0e7da6 from the openjdk/jdk repository.

The commit being backported was authored by Tobias Hartmann on 27 Feb 2024 and was reviewed by Christian Hagedorn and Vladimir Kozlov.

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If you need to update the source branch of the pull then run the following commands in a local clone of your personal fork of openjdk/jdk22u:

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$ git checkout backport-TobiHartmann-9f0e7da6
# make changes
$ git add paths/to/changed/files
$ git commit --message 'Describe additional changes made'
$ git push https://github.com/openjdk-bots/jdk22u.git backport-TobiHartmann-9f0e7da6

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TobiHartmann added 3 commits February 26, 2024 09:27

8326638: Crash in PhaseIdealLoop::remix_address_expressions due to un…

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…expected Region instead of Loop

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Skip optimization for irreducible loops

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8326638: Crash in PhaseIdealLoop::remix_address_expressions due to unexpected Region instead of Loop #18002

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8326638: Crash in PhaseIdealLoop::remix_address_expressions due to unexpected Region instead of Loop #18002

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