8373355: C2: CompileCommand PrintIdealPhase should also print nodes that are not "reachable from below" by eme64 · Pull Request #28762 · openjdk/jdk

eme64 · 2025-12-11T08:40:42Z

PrintIdealPhase seems to only traverse the graph "from below". So if there are any nodes that are not reachable "from below" but only reachable "from above", then they do not show up in the printing.
That is problematic: out TestFramework relies on that output, especially if you have some IR rule with failOn or count = 0 . The node would be in the graph, but the test tells you there is none.

Before the fix, we used to see this:
The LoadI and StoreI do NOT show up during ITER_GVN1.
This is because at that point, the infinite loop has no exit. So the loop is not connected down to Root.
But once we do a first loop opts round, we see the LoadI and StoreI in PHASEIDEALLOOP1.
This is because we insert a NeverBranch, which serves as an artificial exit, that connects the loop down to Root.

Fix: travese both up + and down -.

Note: I had to update some tests from #22786.
This is because during IGVN the constant nodes that lose all outputs are not removed. So now they show up in the IR graph, and the IR rules failed. I adjusted the IR rules to work with the operations ModF/ModD rather than constants ConF/ConD.

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Issue

JDK-8373355: C2: CompileCommand PrintIdealPhase should also print nodes that are not "reachable from below" (Enhancement - P4)

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Roberto Castañeda Lozano (@robcasloz - Reviewer)
Benoît Maillard (@benoitmaillard - Committer) Review applies to 769640f2
Marc Chevalier (@marc-chevalier - Committer)

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bridgekeeper · 2025-12-11T08:42:31Z

👋 Welcome back epeter! 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 · 2025-12-11T08:43:10Z

@eme64 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:

8373355: C2: CompileCommand PrintIdealPhase should also print nodes that are not "reachable from below"

Reviewed-by: rcastanedalo, mchevalier, bmaillard

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 82 new commits pushed to the master branch:

78c2d57: 8373668: Add override keyword to *Klass classes
b1e8c4e: 8372543: Shenandoah: undercalculated the available size when soft max takes effect
3f33eaa: 8373649: Convert simple AtomicAccess usage in ConcurrentHashTable to use Atomic
... and 79 more: https://git.openjdk.org/jdk/compare/a4eb57c5ec6254e59e486042015dd00457284ef2...master

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openjdk · 2025-12-11T08:43:59Z

@eme64 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 · 2025-12-15T12:43:06Z

Webrevs

robcasloz

Looks good, thanks for fixing this!

test/hotspot/jtreg/testlibrary_tests/ir_framework/tests/TestIRFindFromAbove.java

…FindFromAbove.java Co-authored-by: Roberto Castañeda Lozano <robcasloz@users.noreply.github.com>

eme64 · 2025-12-15T13:47:49Z

@robcasloz Thanks for reviewing and the approval :)

benoitmaillard

Looks good to me, thanks for fixing :)

marc-chevalier

Very fine!

marc-chevalier · 2025-12-16T08:26:36Z

test/hotspot/jtreg/compiler/c2/irTests/ModDNodeTests.java

        Asserts.assertEQ(unusedResultAfterLoopOpt3(1.1d, 2.2d), 0.d);
    }

+    // Note: we used to check for ConF nodes in the IR. But that is a bit brittle:


ConD in this case.

Nice catch!

test/hotspot/jtreg/compiler/c2/irTests/ModDNodeTests.java

eme64 · 2025-12-16T08:48:45Z

@marc-chevalier @benoitmaillard @robcasloz Thanks for the reviews!

I'll need another approval because of the minor fix so I can integrate ;)

marc-chevalier

My review isn't enough, right?

eme64 · 2025-12-16T09:33:49Z

@robcasloz @benoitmaillard @marc-chevalier Thanks for the reviews and approvals :)

/integrate

openjdk · 2025-12-16T09:34:43Z

Going to push as commit 8402891.
Since your change was applied there have been 82 commits pushed to the master branch:

78c2d57: 8373668: Add override keyword to *Klass classes
b1e8c4e: 8372543: Shenandoah: undercalculated the available size when soft max takes effect
3f33eaa: 8373649: Convert simple AtomicAccess usage in ConcurrentHashTable to use Atomic
... and 79 more: https://git.openjdk.org/jdk/compare/a4eb57c5ec6254e59e486042015dd00457284ef2...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-12-16T09:35:01Z

@eme64 Pushed as commit 8402891.

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

JDKJDK-8373355

2c7a425

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Dec 11, 2025

eme64 changed the title ~~JDKJDK-8373355~~ JDK-8373355 Dec 11, 2025

openjdk bot changed the title ~~JDK-8373355~~ 8373355: C2: CompileCommand PrintIdealPhase should also print nodes that are not "reachable from below" Dec 11, 2025

eme64 added 3 commits December 11, 2025 16:56

wip fixing ModFNodeTests.java

71a4072

wip

a3c18f1

fixed up other test

d77e683

eme64 marked this pull request as ready for review December 15, 2025 12:38

openjdk bot added the rfr Pull request is ready for review label Dec 15, 2025

robcasloz approved these changes Dec 15, 2025

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test/hotspot/jtreg/testlibrary_tests/ir_framework/tests/TestIRFindFromAbove.java Outdated Show resolved Hide resolved

Update test/hotspot/jtreg/testlibrary_tests/ir_framework/tests/TestIR…

769640f

…FindFromAbove.java Co-authored-by: Roberto Castañeda Lozano <robcasloz@users.noreply.github.com>

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eme64 commented Dec 16, 2025

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test/hotspot/jtreg/compiler/c2/irTests/ModDNodeTests.java Outdated Show resolved Hide resolved

Suggestion by Marc

42ce8ed

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