[6.2][SILOptimizer]: slow OSSA lifetime canonicalization mitigation #82402
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Contributor
jamieQ
commented
Jun 22, 2025
jamieQ
commented
- Explanation: adds logic expected to speed up compile time when canonicalizing OSSA lifetimes
- Scope: no behavioral change is expected, aside from improved compilation time scaling as basic block sizes grow
- Issues: Poor scaling with optimized builds involving OSSA & copy propagation in the 6.2 compiler #82317
- Original PRs: [SILOptimizer]: slow OSSA lifetime canonicalization mitigation #82313
- Risk: low – no behavioral changes expected
- Testing: new function test added for DeadEndBlock utility method; existing test cases confirmed to cover the newly-introduced conditional logic
- Reviewers: @nate-chandler
OSSA lifetime canonicalization can take a very long time in certain cases in which there are large basic blocks. to mitigate this, add logic to skip walking the liveness boundary for extending liveness to dead ends when there aren't any dead ends in the function. Updates `DeadEndBlocks` with a new `isEmpty` method and cache to determine if there are any dead-end blocks in a given function. (cherry picked from commit 1f3f830)
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@swift-ci please test |
tbkka
approved these changes
Jun 22, 2025
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