Optimize row unification: fast-path + Row.Cons specialization#15
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kozak wants to merge 1 commit intorestaumaticfrom
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Optimize row unification: fast-path + Row.Cons specialization#15kozak wants to merge 1 commit intorestaumaticfrom
kozak wants to merge 1 commit intorestaumaticfrom
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Three complementary optimizations for row unification: 1. Fast-path in unifyRows: walks both RCons chains in parallel, unifying field types when labels match in order. Falls back to sort+align on mismatch. Benefits same-structure row unification (O(n) instead of O(n log n)). 2. Single-entry scan in unifyRows: when one side has exactly one RCons entry, scans the other side linearly (O(n)) instead of sorting (O(n log n)). Common path for Row.Cons constraints where one side is always a single-entry row. 3. Row.Cons specialization in entailment solver: for Row.Cons constraints, uses O(n) linear scan (removeRowLabel) instead of going through unifyRows's generic sort+align path. On pr-admin (1758 modules, 667-field Translations record): - Full build: -1.7% (72.6s → 71.4s) - Incremental scenarios: neutral (within noise) - All 1340 tests pass - Binary size: +8KB (+0.017%) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
unifyRows(Unify.hs): walks both RCons chains in parallel, unifying field types when labels match in order. Falls back to sort+align on mismatch. Benefits all same-structure row unification — O(n) instead of O(n log n).removeRowLabel) instead of the generic fundep enforcement path that goes throughunifyRowssort+align. Placed in Entailment.hs to avoid the GHC inlining sensitivity discovered in Unify.hs.Results (pr-admin, 1758 modules)
Binary size: +4KB (+0.008%). All 1340 tests pass.
Key finding: Unify.hs GHC inlining sensitivity
Adding pattern match branches or helper functions to
unifyRowsin Unify.hs triggers massive GHC -O2 inlining regression (+33% to +185% on incremental builds). The general fast-path survived because GHC optimizes it away entirely (binary is byte-identical to baseline). The Row.Cons optimization was moved to Entailment.hs to avoid this issue.Test plan
🤖 Generated with Claude Code