[PROOF / DO NOT MERGE] Release determinism CI is broken on main#19859
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T-Gro wants to merge 1 commit into
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[PROOF / DO NOT MERGE] Release determinism CI is broken on main#19859T-Gro wants to merge 1 commit into
T-Gro wants to merge 1 commit into
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This draft demonstrates that the current main branch is non-deterministic in Release configuration. 8 parallel iterations maximize the probability that pre-existing races (TypeDefsBuilder counter, ConcurrentStack drain, parallel optimizer Val.Stamp iteration order) trigger at least once. DO NOT MERGE. Evidence-only PR for #19732 / #19810. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Purpose
Evidence-only draft. This branch contains no product changes — only a CI configuration flip from
DebugtoReleasefor theDeterminismjob, with 8 parallel iterations to maximize the probability of catching probabilistic races on a single CI run.Hypothesis
Multiple non-determinism races exist on current main, not visible because the existing CI
Determinism_Debugjob disables the optimizer (SetOptimizeOfffor Debug):#Stringsheap layout #19732) — parallel optimizer iteratesValsets by racyVal.Stamp(Interlocked.Incrementglobally assigned)IlxGen.TypeDefsBuilder.AddTypeDef— counter-based type ordering races under parallel codegenGrabExtraBindingsToGenerate—ConcurrentStackdrain order is non-deterministicNiceNameGenerator— global singleton counter across other callersFileIndex— assignment race under parallel parseIf any of these fire in any of the 8 iterations, we see hash mismatches on
FSharp.Compiler.Service.dlletc.Why this matters
PR #19810 fixes (1) but cannot land confidently while (2)-(5) remain hidden. This PR establishes the baseline: Release determinism CI currently fails. Subsequent PRs (#19810 + follow-ups) must drive it back to green by fixing the product, not by reverting CI to Debug.
What to look at
Determinism_Release iter1..iter8job results!=(hash mismatch) andFiles have different contentRelated: #19732, #19810