8315920: C2: "control input must dominate current control" assert failure #15720

rwestrel · 2023-09-13T14:35:55Z

The assert fires during range check eliminationin code that was added
recently. It catches a bug that's been going unnoticed. The array[0]
load of the test case ends up on the exit of the loop above it. After
pre/main/post loops are created for this loop (the inner loop is
optimized out), the load is at a region merging control from the just
created pre/main/post loops but its control (as returned by
PhaseIdealLoop::get_ctrl()) is not updated by pre/main/post loops
creation code so it's still the exit projection of one of the
loops. This causes the assert to fire (the load has bad control) when
RC runs next in the same loop opts pass.

The current logic for pre/main/post loops creation does update the
control of nodes on an exit projection but only if the node is
referenced from some other node in the loop body.

I think a similar bug with a node assigned control at the exit but not
pinned is likely to exist. So I doubt simply going over nodes pinned
at exits during pre/main/post and updating their control is good
enough. What I propose instead is to lazy_replace() the projection
by the region so that, for all nodes that are assigned the exit as
control, get_ctrl() will then return the region. It's not entirely
straightforward to implement because the lazy_replace() mechanism
assumes the control being replaced is dead which is not the case
here. That's why in the patch the exit projection is cloned so the
existing one is dead and can be used in lazy_replace(). This also
makes the calls to sink_use() redundant.

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Issue

JDK-8315920: C2: "control input must dominate current control" assert failure (Bug - P3)

Reviewers

Tobias Hartmann (@TobiHartmann - Reviewer) ⚠️ Review applies to 321a7244
Christian Hagedorn (@chhagedorn - Reviewer)

Reviewing

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Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk.git pull/15720/head

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bridgekeeper · 2023-09-13T14:37:21Z

👋 Welcome back roland! 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 · 2023-09-13T14:39:29Z

@rwestrel 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.

mlbridge · 2023-09-13T14:44:05Z

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TobiHartmann

This looks good to me but needs some more comments.

TobiHartmann · 2023-09-15T13:02:14Z

src/hotspot/share/opto/loopTransform.cpp

  post_head->set_normal_loop();
  post_head->set_post_loop(main_head);

+  main_exit = outer_main_end->proj_out(false);


Please add a comment explaining that/why the main_exit projection changed.

src/hotspot/share/opto/loopopts.cpp

TobiHartmann · 2023-09-15T13:14:11Z

src/hotspot/share/opto/loopopts.cpp

      }
-
-      // If 'use' was in the loop-exit block, it now needs to be sunk
-      // below the post-loop merge point.


This comment needs to be moved to the new lazy-replace logic and cloning needs to be explained there as well.

openjdk · 2023-09-15T13:48:26Z

@rwestrel 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:

8315920: C2: "control input must dominate current control" assert failure

Reviewed-by: thartmann, chagedorn

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 96 new commits pushed to the master branch:

20ff603: 8316735: Print LockStack in hs_err files
e510dee: 8316098: Revise signature of numa_get_leaf_groups
1513e79: 8316940: Serial: Remove unused declarations in genCollectedHeap
52983ed: 8303737: C2: Load can bypass subtype check that enforces it's from the right object type
9e6cb62: 8316851: Add @sealedGraph to Executable
3fe6e0f: 8308479: [s390x] Implement alternative fast-locking scheme
e2e8e8e: 8312136: Modify runtime/ErrorHandling/TestDwarf.java to split dwarf and decoder testing
0dce4c1: 8313220: Remove Windows specific workaround in LCMS.c for _snprintf
e5f05b5: 8312191: ColorConvertOp.filter for the default destination is too slow
be9cc73: 8315871: Opensource five more Swing regression tests
... and 86 more: https://git.openjdk.org/jdk/compare/62c0a1b9ac6462233f3ee06af470be9844e9e226...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.

chhagedorn

Looks good to me, too.

chhagedorn · 2023-09-20T13:55:03Z

src/hotspot/share/opto/loopopts.cpp

        }

+        assert(use->is_Proj(), "loop exit should be projections");
+        Node* use_clone = use->clone();


Maybe also add a comment here why you need to clone the node for lazy_replace().

src/hotspot/share/opto/loopopts.cpp

Co-authored-by: Tobias Hartmann <tobias.hartmann@oracle.com>

Co-authored-by: Christian Hagedorn <christian.hagedorn@oracle.com>

rwestrel · 2023-09-25T13:38:46Z

@TobiHartmann @chhagedorn thanks for reviewing this. I pushed a new commit with comments. Let me know if that looks ok to you.

TobiHartmann

Looks good to me, thanks for adding the comments!

src/hotspot/share/opto/loopopts.cpp

Co-authored-by: Tobias Hartmann <tobias.hartmann@oracle.com>

chhagedorn

Thanks for the update, looks good!

rwestrel · 2023-09-26T14:30:11Z

@TobiHartmann @chhagedorn thanks for the reviews.

rwestrel · 2023-09-26T14:30:18Z

/integrate

openjdk · 2023-09-26T14:32:57Z

Going to push as commit 4e1e579.
Since your change was applied there have been 97 commits pushed to the master branch:

1f7dfda: 8316671: sun/security/ssl/SSLSocketImpl/SSLSocketCloseHang.java test fails intermittent with Read timed out
20ff603: 8316735: Print LockStack in hs_err files
e510dee: 8316098: Revise signature of numa_get_leaf_groups
1513e79: 8316940: Serial: Remove unused declarations in genCollectedHeap
52983ed: 8303737: C2: Load can bypass subtype check that enforces it's from the right object type
9e6cb62: 8316851: Add @sealedGraph to Executable
3fe6e0f: 8308479: [s390x] Implement alternative fast-locking scheme
e2e8e8e: 8312136: Modify runtime/ErrorHandling/TestDwarf.java to split dwarf and decoder testing
0dce4c1: 8313220: Remove Windows specific workaround in LCMS.c for _snprintf
e5f05b5: 8312191: ColorConvertOp.filter for the default destination is too slow
... and 87 more: https://git.openjdk.org/jdk/compare/62c0a1b9ac6462233f3ee06af470be9844e9e226...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-09-26T14:33:04Z

@rwestrel Pushed as commit 4e1e579.

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

fix & test

d5af551

openjdk bot added the rfr Pull request is ready for review label Sep 13, 2023

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Sep 13, 2023

TobiHartmann approved these changes Sep 15, 2023

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openjdk bot added the ready Pull request is ready to be integrated label Sep 15, 2023

chhagedorn approved these changes Sep 20, 2023

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rwestrel and others added 6 commits September 25, 2023 14:55

Update src/hotspot/share/opto/loopopts.cpp

e1e8cdf

Co-authored-by: Tobias Hartmann <tobias.hartmann@oracle.com>

Update src/hotspot/share/opto/loopopts.cpp

f49d81f

Co-authored-by: Tobias Hartmann <tobias.hartmann@oracle.com>

Update src/hotspot/share/opto/loopopts.cpp

58ed217

Co-authored-by: Tobias Hartmann <tobias.hartmann@oracle.com>

Update src/hotspot/share/opto/loopopts.cpp

a084584

Co-authored-by: Christian Hagedorn <christian.hagedorn@oracle.com>

Merge branch 'master' into JDK-8315920

b0d9422

comments

321a724

TobiHartmann approved these changes Sep 25, 2023

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src/hotspot/share/opto/loopopts.cpp Outdated Show resolved Hide resolved

Update src/hotspot/share/opto/loopopts.cpp

886f964

Co-authored-by: Tobias Hartmann <tobias.hartmann@oracle.com>

chhagedorn approved these changes Sep 26, 2023

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openjdk bot added the integrated Pull request has been integrated label Sep 26, 2023

openjdk bot closed this Sep 26, 2023

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Sep 26, 2023

This was referenced Oct 20, 2025

8369898: C2 SuperWord: assert(has_ctrl(i)) failed: should be control, not loop #27889

Closed

8370220: C2: rename methods and improve documentation around get_ctrl and idom lazy updating/forwarding of ctrl and idom via dead ctrl nodes #27892

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8315920: C2: "control input must dominate current control" assert failure #15720

8315920: C2: "control input must dominate current control" assert failure #15720

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