8344668: Unnecessary array allocations and copying in TextLine

[gredler]

When LineBreakMeasurer is used to break text into lines, internally it uses TextMeasurer and TextLine to do the job. In the common case, TextLine.getComponents(...) allocates a TextLineComponent[] with room for a single array entry, and passes it to TextLine.createComponentsOnRun(...), which fills the array and returns it, optionally resizing to a larger array if necessary, after which the array is resized back down to actual size (if necessary).

Unfortunately TextLine.createComponentsOnRun(...) is too eager in allocating larger arrays. In the most common case of a single component, this means that a single-element array is allocated, then a 9-element array is allocated (via expandArray(...)), and then another single-element array is allocated (to shrink the array back to actual size). Only one array allocation is necessary in this common case, and no array copying is needed.

---

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Issue

• JDK-8344668: Unnecessary array allocations and copying in TextLine (Bug - P5)

Reviewers

• Phil Race (@prrace - Reviewer) Review applies to bb7a66ce
• Harshitha Onkar (@honkar-jdk - Reviewer)
• Alexander Zvegintsev (@azvegint - Reviewer)

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[bridgekeeper]

👋 Welcome back dgredler! 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]

@gredler This change now passes all automated pre-integration checks.

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

8344668: Unnecessary array allocations and copying in TextLine

Reviewed-by: honkar, azvegint, prr

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At the time when this comment was updated there had been 609 new commits pushed to the master branch:

• 874d68a: 8343747: C2: TestReplicateAtConv.java crashes with -XX:MaxVectorSize=8
• d9a2213: 8345299: C2: some nodes can still have incorrect control after do_range_check()
• 2286fae: 8345159: RISCV: Fix -Wzero-as-null-pointer-constant warning in emit_static_call_stub
• 8403285: 8268145: [macos] Rendering artifacts is seen when text inside the JTable with TableCellEditor having JTextfield
• aa38284: 8345435: Eliminate tier1_compiler_not_xcomp group
• 9284602: 8345628: [BACKOUT] JDK-8287122 Use gcc12 -ftrivial-auto-var-init=pattern in debug builds
• 41c8971: 8287122: Use gcc12 -ftrivial-auto-var-init=pattern in debug builds
• 5da0eee: 8285692: Enable _FORTIFY_SOURCE=2 when building with Clang
• daa2ba5: 8339622: Regression in make open-hotspot-xcode-project
• 6f6bce5: 8344559: Log is spammed by missing pandoc warnings when building man pages
• ... and 599 more: https://git.openjdk.org/jdk/compare/84c99fb91ffc4bfbc2fb0f20f558603d5660d7f1...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.

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[openjdk]

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

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[mlbridge]

Webrevs

• 02: Full - Incremental (557a3b18)
• 01: Full - Incremental (4ca6782f)
• 00: Full (bb7a66ce)

[prrace]

I see. This is very wasteful.

[gredler]

@mrserb Would you have a few free cycles to provide the second review for this PR?

[prrace]

@azvegint @TejeshR13 @prsadhuk @honkar-jdk - this needs a 2nd reviewer

[honkar-jdk]

@gredler There is one other place where expandArray() is called similarly - TextLine.getComponents().

[gredler]

@honkar-jdk Good catch -- I've gone ahead and fixed that one, too.

[honkar-jdk]

LGTM. Ran awt/font and java/awt/font/LineBreakMeasurer tests with fix and they work as expected.

@gredler Missed mentioning it earlier, copyright year needs to be updated for TextLine.java

[gredler]

@honkar-jdk Done! Let me know if there's anything else that catches your eye.

[honkar-jdk]

@honkar-jdk Done! Let me know if there's anything else that catches your eye.

Looks good now. Re-approved.

[gredler]

/integrate

[openjdk]

@gredler
Your change (at version 557a3b1) is now ready to be sponsored by a Committer.

[gredler]

@prrace I think this is ready to be sponsored. Thanks!

[azvegint]

/sponsor

[openjdk]

Going to push as commit f6021a9.
Since your change was applied there have been 609 commits pushed to the master branch:

• 874d68a: 8343747: C2: TestReplicateAtConv.java crashes with -XX:MaxVectorSize=8
• d9a2213: 8345299: C2: some nodes can still have incorrect control after do_range_check()
• 2286fae: 8345159: RISCV: Fix -Wzero-as-null-pointer-constant warning in emit_static_call_stub
• 8403285: 8268145: [macos] Rendering artifacts is seen when text inside the JTable with TableCellEditor having JTextfield
• aa38284: 8345435: Eliminate tier1_compiler_not_xcomp group
• 9284602: 8345628: [BACKOUT] JDK-8287122 Use gcc12 -ftrivial-auto-var-init=pattern in debug builds
• 41c8971: 8287122: Use gcc12 -ftrivial-auto-var-init=pattern in debug builds
• 5da0eee: 8285692: Enable _FORTIFY_SOURCE=2 when building with Clang
• daa2ba5: 8339622: Regression in make open-hotspot-xcode-project
• 6f6bce5: 8344559: Log is spammed by missing pandoc warnings when building man pages
• ... and 599 more: https://git.openjdk.org/jdk/compare/84c99fb91ffc4bfbc2fb0f20f558603d5660d7f1...master

Your commit was automatically rebased without conflicts.

[openjdk]

@azvegint @gredler Pushed as commit f6021a9.

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