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feat(minifier): minimize switch statements#17523

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armano2 wants to merge 67 commits into
oxc-project:mainfrom
armano2:feat/minimize-switch
Closed

feat(minifier): minimize switch statements#17523
armano2 wants to merge 67 commits into
oxc-project:mainfrom
armano2:feat/minimize-switch

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@armano2

@armano2 armano2 commented Dec 31, 2025 •
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Phase 3: Advanced Optimizations

  • Switch statement optimization

changes:

  • converts 1-case and 2-case switches into more compact if or if/else statements when safe.
  • removes redundant empty case suffixes at the end of a switch.
  • removes empty switches (preserving the discriminant if it has side effects) and redundant trailing break statements.

note:

  • i left couple of todo's for later additions, that could add additional optimizations, i can remove them if needed
  • all packages seem to be affected due to napi last break removal from switch cases

future improvements:

  • we could remove all empty cases if there is no default or when its empty as long as test has no side effects
  • in-lining of switches with constant discriminants
  • merge of identical consequent cases without side effects

fixes #17544

@github-actions github-actions Bot added A-minifier Area - Minifier C-enhancement Category - New feature or request labels Dec 31, 2025
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codspeed-hq Bot commented Dec 31, 2025 •
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Merging this PR will not alter performance

✅ 57 untouched benchmarks
⏩ 19 skipped benchmarks1

Comparing armano2:feat/minimize-switch (7b56e64) with main (ba65790)

Open in CodSpeed

Footnotes

  1. 19 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

@github-actions github-actions Bot added A-linter Area - Linter A-parser Area - Parser A-cli Area - CLI A-linter-plugins Area - Linter JS plugins labels Dec 31, 2025
@armano2
armano2 marked this pull request as ready for review December 31, 2025 19:32
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armano2 commented Dec 31, 2025

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i'm pretty bad at naming stuff, suggestions are welcome 😄

armano2
armano2 commented Dec 31, 2025
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Comment thread tasks/minsize/minsize.snap Outdated
@armano2 armano2 mentioned this pull request Jul 14, 2026
Merged
Dunqing pushed a commit that referenced this pull request Jul 14, 2026
@armano2
test(minifier): add test cases for switch statement optimizations (#2…
ca4a4a7 
…4511)

Add baseline test cases for switch statement optimization, extracted
from #17523
@armano2 armano2 mentioned this pull request Jul 14, 2026
Merged
@armano2 armano2 mentioned this pull request Jul 15, 2026
Merged
Dunqing pushed a commit that referenced this pull request Jul 15, 2026
@armano2
feat(minifier): drop empty switch statements (#24527)
91541dd 
Replaces empty switch statements with its discriminant as expression
statement

based on findings from #17523
armano2 added 12 commits July 15, 2026 03:34
@armano2
Merge remote-tracking branch 'upstream/main' into fix/switch-collapsi…
af04e24 
…ng-improvement
@armano2
fix: correct issue from code review
1399377
@armano2
fix: add missing case without default and with fallthrough
b3d64a0
@armano2
fix: change switch_case_is_empty to switch_case_is_empty and always c…
fd287b4 
…heck side effects in test
@armano2
fix: do not check for empty cases if default is non empty or is not i…
906a16a 
…n last
@armano2
fix: simplify logic used to drop expressions
5eee41e
@armano2
fix: update comments
4f8b62b
@armano2
Merge remote-tracking branch 'upstream/main' into fix/switch-collapsi…
2231f39 
…ng-improvement
@armano2
fix: drop unnecessary var
4a9cbde
@armano2
Merge remote-tracking branch 'upstream/main' into fix/switch-collapsi…
ec94ce7 
…ng-improvement
@armano2
Merge remote-tracking branch 'upstream/main' into feat/minimize-switch
9ed0057
@armano2
Merge branch 'fix/switch-collapsing-improvement' into feat/minimize-s…
996d1b4 
…witch
@armano2
armano2 marked this pull request as draft July 15, 2026 22:57
Dunqing added a commit that referenced this pull request Jul 16, 2026
@armano2 @Dunqing
feat(minifier): expand switch optimiation to remove empty cases (#24520)
3acf4c1 
remove empty cases:
- before default or at end (if no default).
- only if they don't affect behavior.

refactored implementation from #17523 

ref #17544

---------

Co-authored-by: Dunqing <[email protected]>
@armano2 armano2 mentioned this pull request Jul 17, 2026
Open
@armano2 armano2 closed this Jul 19, 2026
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@camc314 camc314 camc314 approved these changes
@overlookmotel overlookmotel Awaiting requested review from overlookmotel overlookmotel is a code owner
@Dunqing Dunqing Awaiting requested review from Dunqing Dunqing is a code owner

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A-cli Area - CLI A-linter Area - Linter A-linter-plugins Area - Linter JS plugins A-minifier Area - Minifier A-parser Area - Parser C-enhancement Category - New feature or request

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minifier: switch statement optimization

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@armano2 @Dunqing @camc314 @overlookmotel @Boshen