8343148: C2: Refactor uses of "PhaseValue::*con*() + PhaseIdealLoop::set_ctrl()" into separate method

[theoweidmannoracle]

This patch introduces the methods PhaseIdealLoop::intcon and PhaseIdealLoop::longcon which are wrappers for:

ConINode* node = _igvn.intcon(i);
set_ctrl(node, C->root());

and

ConLNode* node = _igvn.longcon(i);
set_ctrl(node, C->root());

Occurrences of this pattern in loopnode.cpp were replaced with the appropriate call to the new methods.

---

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Issue

• JDK-8343148: C2: Refactor uses of "PhaseValue::con() + PhaseIdealLoop::set_ctrl()" into separate method (Enhancement - P4)

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer)
• Christian Hagedorn (@chhagedorn - Reviewer)
• Tobias Hartmann (@TobiHartmann - Reviewer)

Reviewing

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[openjdk]

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After integration, the commit message for the final commit will be:

8343148: C2: Refactor uses of "PhaseValue::*con*() + PhaseIdealLoop::set_ctrl()" into separate method

Reviewed-by: kvn, chagedorn, thartmann

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At the time when this comment was updated there had been 627 new commits pushed to the master branch:

• 1e9204f: 8345273: Fix -Wzero-as-null-pointer-constant warnings in s390 code
• c40140e: 8334581: Remove no-arg constructor BasicSliderUI()
• 8de0622: 8345767: javax/swing/JSplitPane/4164779/JSplitPaneKeyboardNavigationTest.java fails in ubuntu22.04
• abcd23f: 8334756: javac crashed on call to non-existent generic method with explicit annotated type arg
• 2ddaa46: 8305010: Test vmTestbase/nsk/jvmti/scenarios/sampling/SP05/sp05t003/TestDescription.java timed out: thread not suspended
• c631719: 8343170: java/awt/Cursor/JPanelCursorTest/JPanelCursorTest.java does not show the default cursor
• 29d648c: 8341781: Improve Min/Max node identities
• 4c39e9f: 8344924: Default CA certificates loaded despite request to use custom keystore
• 0f03554: 8342469: Improve API documentation for java.lang.classfile.instruction
• 9bd70ec: 8345888: Broken links in the JDK 24 JavaDoc API documentation, build 27
• ... and 617 more: https://git.openjdk.org/jdk/compare/5b2f7f3b30adf9942fa8a3382e7661d6816fbb38...master

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[chhagedorn]

While at it, we could extend this to the other constant creation methods zerocon, makecon, and integercon as well (uncached_makecon is only called by the other *con* methods - could be made private at some point). I suggest to update the RFE title accordingly since it only mentions intcon now. Maybe something like PhaseValue::*con*() + ....

[mlbridge]

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[vnkozlov]

Do we have other places (not new constant node) where we set Root as control?
May be we can add set_root_as_ctrl(n) method in loop node.hpp in such case.

[vnkozlov]

Do we have other places (not new constant node) where we set Root as control?

In loop opts.

[theoweidmannoracle]

Do we have other places (not new constant node) where we set Root as control? May be we can add set_root_as_ctrl(n) method in loop node.hpp in such case.

There's only three locations where control is set to the root in the loop files now (not counting the ones in the new methods I added). The main reason for this patch is bugs caused by people forgetting to set control for constants (e.g. https://bugs.openjdk.org/browse/JDK-8343137), which is now prevented if the new helper methods are used.

Do you think there would be any benefit from introducing set_root_as_ctrl(n) given there's only about three places where this pattern occurs now?

[vnkozlov]

Do we have other places (not new constant node) where we set Root as control? May be we can add set_root_as_ctrl(n) method in loop node.hpp in such case.

There's only three locations where control is set to the root in the loop files now (not counting the ones in the new methods I added). The main reason for this patch is bugs caused by people forgetting to set control for constants (e.g. https://bugs.openjdk.org/browse/JDK-8343137), which is now prevented if the new helper methods are used.

Do you think there would be any benefit from introducing set_root_as_ctrl(n) given there's only about three places where this pattern occurs now?

My suggesting is about additional cleaning code. I think 3 + 5 places are enough to justify to have a new function in header file. Also set_root_as_ctrl(n) could be copy of set_ctrl(n, ctrl) without 2 asserts which checks ctrl. It will be faster.

[theoweidmannoracle]

@vnkozlov I implemented your suggestion. Would you like to take another look? (It also helped me discover some more cases which can be replaced with the new *con*() functions.)

[vnkozlov]

Looks good. I have few additional comments.

[vnkozlov]

Please look on history of this code. This is suspicious - constant nodes should be always attached to Root.

[theoweidmannoracle]

@TobiHartmann Pointed out that this method is also called from code outside of loop opts, for example, PhaseMacroExpand::expand_macro_nodes. Since there's no PhaseIdealLoop in this case, nullptr is passed instead and we cannot set control as we are not inside a loop opt.

Maybe @rwestrel can also take a look as he originally introduced this code in this PR.

[vnkozlov]

Got it. That is what (iloop != nullptr) check for.

[openjdk]

@theoweidmannoracle this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout JDK-8343148
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[chhagedorn]

Some last minor comments, otherwise the updates look good to me. Thanks for doing this extended refactoring!

[theoweidmannoracle]

@vnkozlov Could you take another look at the latest changes?

[TobiHartmann]

Looks good to me. Nice cleanup.

[vnkozlov]

This version looks good.

[theoweidmannoracle]

/integrate

[openjdk]

@theoweidmannoracle
Your change (at version 4ed14b2) is now ready to be sponsored by a Committer.

[chhagedorn]

/sponsor

[openjdk]

Going to push as commit e88e793.
Since your change was applied there have been 627 commits pushed to the master branch:

• 1e9204f: 8345273: Fix -Wzero-as-null-pointer-constant warnings in s390 code
• c40140e: 8334581: Remove no-arg constructor BasicSliderUI()
• 8de0622: 8345767: javax/swing/JSplitPane/4164779/JSplitPaneKeyboardNavigationTest.java fails in ubuntu22.04
• abcd23f: 8334756: javac crashed on call to non-existent generic method with explicit annotated type arg
• 2ddaa46: 8305010: Test vmTestbase/nsk/jvmti/scenarios/sampling/SP05/sp05t003/TestDescription.java timed out: thread not suspended
• c631719: 8343170: java/awt/Cursor/JPanelCursorTest/JPanelCursorTest.java does not show the default cursor
• 29d648c: 8341781: Improve Min/Max node identities
• 4c39e9f: 8344924: Default CA certificates loaded despite request to use custom keystore
• 0f03554: 8342469: Improve API documentation for java.lang.classfile.instruction
• 9bd70ec: 8345888: Broken links in the JDK 24 JavaDoc API documentation, build 27
• ... and 617 more: https://git.openjdk.org/jdk/compare/5b2f7f3b30adf9942fa8a3382e7661d6816fbb38...master

Your commit was automatically rebased without conflicts.

[openjdk]

@chhagedorn @theoweidmannoracle Pushed as commit e88e793.

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