2026 EuroLLVM - Toward A More Declarative InstCombine: Generalization & Parametric Bitvector...

2026 EuroLLVM Developers' Meeting https://llvm.org/devmtg/2026-04/ ------ Title: Toward A More Declarative InstCombine: Generalization & Parametric Bitvector Algorithms Speaker: Siddharth Bhat ------ Slides: https://llvm.org/devmtg/2026-04/slide... ----- LLVM contains thousands of bitwidth-dependent rewrites that are hard to maintain and reason about. We introduce new parametric bitvector algorithms that automatically generalize these rewrites across all widths. By applying a mixed unary-binary encoding and finite-state reasoning, our solver lifts concrete LLVM test cases into true width-independent identities, recovering parametric rewrites from LLVM's test suite that has fixed width rewrites. This moves LLVM toward a declarative InstCombine specification, where rewrite rules are uniform, provably correct, and mechanically derived. ----- Videos Edited by Bash Films: http://www.BashFilms.com