8373396: Min and Max Ideal missing AddNode::Ideal optimisations by galderz · Pull Request #28770 · openjdk/jdk

galderz · 2025-12-11T16:02:24Z

MaxI and MinI are missing AddNode::Ideal optimizations. These optimizations include commutation, flattening, pushing constants...etc. The PR changes MaxINode::Ideal and MinINode::Ideal to call AddNode::Ideal. Long versions already call AddNode::Ideal so nothing to change there.

The PR also includes a template framework generated test (cc @eme64) that verifies that all of AddNode::Ideal optimizations now apply correctly for min/max for longs and ints. Long tests have been added to validate that both ints and longs produce the same results.

Fixing this issue indirectly fixes compiler/codegen/TestBooleanVect.java when run with -XX:VerifyIterativeGVN=1110, which was failing due to min not having one of those optimisations. However, this PR does not make changes to PhaseIterGVN::verify_Identity_for because there are additional failures observed with min/max for integers in JDK-8373134. Therefore, changes there will in the PR for JDK-8373134 instead.

Update 15.12.25: PhaseIterGVN::verify_Ideal_for exceptions for MinI/MaxI are still needed.

If you look at PhaseIterGVN::verify_Ideal_for, it contains. This looks like it could be removed in this PR as it looks like they were quite likely disabled due to the issue here. However, it's unclear what test was failing here (@eme64 ?):

    // MinINode::Ideal
    // Did not investigate, but there are some patterns that might
    // need more notification.
    case Op_MinI:
    case Op_MaxI: // preemptively removed it as well.
      return false;

I've run tier1-3 tests on linux/x64 and they passed.

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Issue

JDK-8373396: Min and Max Ideal missing AddNode::Ideal optimisations (Enhancement - P4)

Reviewers

Emanuel Peter (@eme64 - Reviewer)
Roland Westrelin (@rwestrel - Reviewer)

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* Optimizations include commutation, flattening, pushing constants...etc. * Added template framework generated test for all optimizations that AddNode::Ideal covers. * Test for ints and longs, both of which call AddNode::Ideal.

bridgekeeper · 2025-12-11T16:04:47Z

👋 Welcome back galder! 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 · 2025-12-11T16:06:35Z

@galderz 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:

8373396: Min and Max Ideal missing AddNode::Ideal optimisations

Reviewed-by: epeter, roland

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 131 new commits pushed to the master branch:

2ba423d: 8370200: Crash: assert(outer->outcnt() >= phis + 2 - be_loads && outer->outcnt() <= phis + 2 + stores + 1) failed: only phis
4f283f1: 8373820: C2: Robust Node::uncast_helper infinite loop check
d8eb125: 8373866: Refactor java/net/httpclient/ThrowingSubscribers*.java tests to use JUnit5
... and 128 more: https://git.openjdk.org/jdk/compare/831fe94c75c407b2399be9b89630d8d117c2996c...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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@eme64, @rwestrel) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

openjdk · 2025-12-11T16:08:01Z

@galderz 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 · 2025-12-11T16:11:24Z

Webrevs

TobiHartmann · 2025-12-12T06:54:18Z

src/hotspot/share/opto/addnode.cpp


 // Ideal transformations for MaxINode
 Node* MaxINode::Ideal(PhaseGVN* phase, bool can_reshape) {
+  Node* n = AddNode::Ideal(phase, can_reshape);


Why not move this into MaxNode::IdealI?

Yes, the call below return IdealI(phase, can_reshape); already looks like it wants to handle all the superclass optimiazations. So it should go in there.

eme64

@galderz Nice, this looks like a good use-case of the template framework, it reduces the test size!

It still feels a bit boiler-plate-y ... but it is a step in the right direction for sure ☺️

eme64 · 2025-12-12T11:22:29Z

src/hotspot/share/opto/addnode.cpp


 // Ideal transformations for MaxINode
 Node* MaxINode::Ideal(PhaseGVN* phase, bool can_reshape) {
+  Node* n = AddNode::Ideal(phase, can_reshape);


Yes, the call below return IdealI(phase, can_reshape); already looks like it wants to handle all the superclass optimiazations. So it should go in there.

eme64 · 2025-12-12T11:24:09Z

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

+ * @summary Verify that min/max add ideal optimizations get applied correctly
+ * @modules java.base/jdk.internal.misc
+ * @library /test/lib /
+ * @run driver compiler.c2.irTests.TestMinMaxIdeal


Suggested change

* @run driver compiler.c2.irTests.TestMinMaxIdeal

* @run driver ${test.main.class}

Also: please don't put any new tests in irTests. Rather put it in a directory based on the topic.

I did think about that but then I saw TestMinMaxIdentities was on the package so thought of adding it next to it. What about putting it in compiler.intrinsics.math instead?

I think it belongs more under idealization. So either a gvn or igvn directory.

eme64 · 2025-12-12T11:25:17Z

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

+        String templatedPackage ="compiler.c2.templated";
+        String templatedClassName ="MinMaxIdeal";
+        String templatedFQN = "%s.%s".formatted(templatedPackage, templatedClassName);


That looks a bit convoluted. Why not just use the final string?

Not sure exactly what you mean. For addJavaSourceCode I need the combined FQN and for TestFrameworkClass.render I need the classname and package separated.

It is just a nit, I leave it to you. I'm also fine taking it as is :)

eme64 · 2025-12-12T13:15:41Z

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

+        testTemplateTokens.add(new TestGenerator(Op.MIN_I).generate());
+        testTemplateTokens.add(new TestGenerator(Op.MAX_I).generate());
+        testTemplateTokens.add(new TestGenerator(Op.MIN_L).generate());
+        testTemplateTokens.add(new TestGenerator(Op.MAX_L).generate());


Why not use Op.values() -> List, then iterate over that?

Yeah, better indeed. It avoids issues adding an enum value and forgetting to add it (I already did that lol)

galderz · 2025-12-12T16:51:25Z

@TobiHartmann Thanks for the review!

@eme64 Thanks also for the review. Can you please also clarify what I said about potentially changing PhaseIterGVN::verify_Ideal_for in the description?

eme64 · 2025-12-12T17:14:31Z

@TobiHartmann Thanks for the review!

@eme64 Thanks also for the review. Can you please also clarify what I said about potentially changing PhaseIterGVN::verify_Ideal_for in the description?

I don't remember. Try enabling the verification, and see if you find any test that fails. If not: great, maybe you fixed it! If it still fails, it would be nice if you added more info, but not neccessary.

I don't remember because there were eventually too many cases and I stopped reporting which had failed.

galderz · 2025-12-15T17:14:49Z

I don't remember. Try enabling the verification, and see if you find any test that fails. If not: great, maybe you fixed it! If it still fails, it would be nice if you added more info, but not neccessary.

It still fails with other optimisation missing, so I will revert that the commit that uncommented that:

----------messages:(7/385)----------
command: main -Xcomp -XX:VerifyIterativeGVN=1111 compiler.c2.TestVerifyIterativeGVN
reason: User specified action: run main/othervm/timeout=300 -Xcomp -XX:VerifyIterativeGVN=1111 compiler.c2.TestVerifyIterativeGVN 
started: Mon Dec 15 09:07:06.937 CET 2025
Mode: othervm [/othervm specified]
Process id: 133090
finished: Mon Dec 15 09:07:45.303 CET 2025
elapsed time (seconds): 38.366
----------configuration:(0/0)----------
----------System.out:(32/1990)----------

Missed Ideal optimization (can_reshape=false):
The node was reshaped by Ideal.
The result after Ideal:
dist dump
---------------------------------------------
   1  1612  AddI  === _ 1880 668  [[ 1258 ]]  !orig=[3471] !jvms: DirectMethodHandle::makePreparedLambdaForm @ bci:612 (line 293)
   1  1254  CastII  === 1519 1606  [[ 881 1258 1879 1607 870 2028 ]]  #int:0..maxint-1, widen: 3 !orig=[5228],[3463] !jvms: DirectMethodHandle::makePreparedLambdaForm @ bci:612 (line 293)
   0  1258  MinI  === _ 1254 1612  [[ 871 ]]  !jvms: DirectMethodHandle::makePreparedLambdaForm @ bci:612 (line 293)

This reverts commit 1ae3081.

galderz · 2025-12-15T17:16:58Z

I've reverted the PhaseIterGVN::verify_Ideal_for changes suggested in the description. Tier1-3 testing looks good otherwise.

@TobiHartmann @eme64 Could you please review it once more? Thanks!

eme64

Looks good now, except that little nit below.

We can run some internal testing once a second reviewer has had a look :)

eme64 · 2025-12-16T07:37:45Z

test/hotspot/jtreg/compiler/igvn/TestMinMaxIdeal.java

+                let("irNodeName", op.name()),
+                let("boxedTypeName", op.type.boxedTypeName()),
+                let("op", op.name()),


Nit: you are repeating the same value op.name() with two hashtags op and irNodeName. Is that intentional?

No, I'll get it fixed

Just pushed a fix

eme64

Nice, looks cleaner now :)

rwestrel

Looks good to me.

galderz · 2025-12-16T11:55:19Z

@eme64 Roland provided the 2nd review so you can start your internal testing.

eme64 · 2025-12-16T13:48:06Z

Testing launched 🚀

eme64 · 2025-12-18T07:03:48Z

Testing passed, ship it 🚢 !

galderz · 2025-12-18T11:42:12Z

/integrate

openjdk · 2025-12-18T11:44:18Z

@galderz
Your change (at version b1ab81b) is now ready to be sponsored by a Committer.

rwestrel · 2025-12-18T11:45:09Z

/sponsor

openjdk · 2025-12-18T11:45:30Z

Going to push as commit 2c0d9a7.
Since your change was applied there have been 131 commits pushed to the master branch:

2ba423d: 8370200: Crash: assert(outer->outcnt() >= phis + 2 - be_loads && outer->outcnt() <= phis + 2 + stores + 1) failed: only phis
4f283f1: 8373820: C2: Robust Node::uncast_helper infinite loop check
d8eb125: 8373866: Refactor java/net/httpclient/ThrowingSubscribers*.java tests to use JUnit5
... and 128 more: https://git.openjdk.org/jdk/compare/831fe94c75c407b2399be9b89630d8d117c2996c...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-12-18T11:45:41Z

@rwestrel @galderz Pushed as commit 2c0d9a7.

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

galderz · 2025-12-18T11:47:41Z

Thanks @eme64 and @rwestrel for the reviews!

galderz added 3 commits December 11, 2025 10:08

Call AddNode::Ideal in MinINode::Ideal to get optimizations

51f65d9

Test that MinI/MinL optimizations apply as expected

2e24111

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

openjdk bot added the rfr Pull request is ready for review label Dec 11, 2025

TobiHartmann reviewed Dec 12, 2025

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eme64 suggested changes Dec 12, 2025

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galderz added 6 commits December 15, 2025 06:13

Move to compiler.igvn package

8fbea99

Use ${test.main.class}

d7ac3eb

Remove variables

df08c5f

Refactor to MaxNode::IdealI

2373291

Iterate over enum values instead

b46526d

Remove MinI/MaxI exceptions from verify_Ideal_for

1ae3081

Revert "Remove MinI/MaxI exceptions from verify_Ideal_for"

630364e

This reverts commit 1ae3081.

eme64 approved these changes Dec 16, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Dec 16, 2025

Fix redundant variable

b1ab81b

openjdk bot removed the ready Pull request is ready to be integrated label Dec 16, 2025

eme64 approved these changes Dec 16, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Dec 16, 2025

rwestrel approved these changes Dec 16, 2025

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openjdk bot added the sponsor Pull request is ready to be sponsored label Dec 18, 2025

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openjdk bot closed this Dec 18, 2025

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review sponsor Pull request is ready to be sponsored labels Dec 18, 2025

galderz deleted the topic.commute-et-al branch December 18, 2025 11:51

	* @run driver compiler.c2.irTests.TestMinMaxIdeal
	* @run driver ${test.main.class}

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