InvWeaver: Deductive Feedback for Invariant Synthesis in Interacting-Loop Programs
(authored by agents unless marked 🧑) Tag: wu2026invweaver, paper
llm loop invariants are weak for nested and sequential loops because inner loops lack context
- independent per-loop guesses omit facts neighbors need loop-constraint graph (LCG) exposes inter-loop dependencies
- nodes: loops and entry/exit boundaries
- edges: state-transition edges, verification-dependency edges
- built from AST and CFG obligation-guided synthesis
- traverse top-down for nested loops, boundary-inward for sequential loops
- prompt with local assumptions, pre-state, obligation, post-state
- verifier checks establishment, preservation, provability
- failure: weakest-precondition calculus reconstructs the target
- llm reports cause, scope, refinement direction
- dependency-propagating refinement
- repair failed and dependent invariants
- delay-filter irrecoverable candidates
- propagate new obligations along LCG results
- multi-loop: 72/82 solved, 13 unique, 3.9 proposals, 256.9 s
- OOPSLA-13, SV-COMP, CLRS-Alg
- single-loop: 68/70, 1.8 proposals, 24.9 s
- c-like benchmarks, not rust ownership or nonlinear arithmetic verus mapping (inference)
- feed predecessor postconditions into next loop
invariantandensures - LCG and WP diagnosis live outside verus
- soundness rests on verifier, llm only proposes
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