Python: cache shared SSA definition reachability - #148
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Allow language-specific SSA instantiations that cross multiple cached API stages to cache the complete definition-rank and end-of-block reachability fixed points. Keep the default factory demand-specialized so unrelated instantiations retain their existing evaluator behavior. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 07c775e7-cd7c-4e1c-8d97-5194ffd43e1a
Select the opt-in cached definition-reachability factory for Python main SSA. The independent capture-SSA instantiation continues to use the default uncached factory. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 07c775e7-cd7c-4e1c-8d97-5194ffd43e1a
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Broad isolated DCA launched: https://github.com/github/codeql-dca-main/issues/38887 Exact comparison: github#22465 |
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Summary
This is a DCA-only stacked draft above github#22465. It is based directly on
yoff-python-cache-shared-ssa-livenessat8791147a0bc72325c35004ab741442cd7de3122d; this layer's head isfc71c20369d455a2ec5fb9969cafeabc62a03ccb.The layer contains two commits:
e9bb6ff417c7a5574ef3f1ff84637b029c10e9ca(SSA: add opt-in definition reachability caching) adds an opt-in shared-SSA factory that caches the complete definition-rank and end-of-block reachability fixed points while keeping the default factory demand-specialized.fc71c20369d455a2ec5fb9969cafeabc62a03ccb(Python: cache shared SSA definition reachability) selects that factory only for Python's main SSA instantiation.Capture SSA remains uncached:
VariableCapture.qllcontinues to instantiate the defaultSsa::Makefactory.Exact local evidence
Clean-cache serial controls retained exact BQRS/result hashes and unchanged complete result-generation hashes for the cached relations:
1,250,313,522 -> 1,243,689,535(-6,623,987,-0.53%), with 525 recursive runs removed.1,087,918,400 -> 1,084,198,621(-3,719,779,-0.34%), with 1,691 recursive runs removed.2,304,605,194 -> 2,241,319,019(-63,286,175,-2.75%), with 6,700 recursive runs removed.The main rank/end-of-block relations collapse from 2/2, 2/2, and 7/6 recursive materializations respectively to one each.
Validation
codeql query format --check-only -- shared/ssa/codeql/ssa/Ssa.qll python/ql/lib/semmle/python/dataflow/new/internal/SsaImpl.qllcodeql test run --search-path=. -- python/ql/test/library-tests/dataflow-new-ssa/SsaTest.ql python/ql/test/library-tests/dataflow-new-ssa/AdjacentUsesContract.qlBoth targeted tests pass.
Cache tradeoff
Tuple pools are unchanged. After clean-cache prewarm plus target and normal cleanup, persistent cache grows by
+7,172 KiBfor Airflow (363,004 -> 370,176 KiB,+1.98%) and+14,860 KiBfor Salt (509,484 -> 524,344 KiB,+2.92%).This draft is for DCA measurement only. It is not a merge proposal.