nx_superopt_strength.nx

nx_superopt_strength.nx -- a GENERATOR: it AUTHORS strength-reduction lowerings for `x * C` by SEARCH, not by me hand-writing each rule. Given a constant C, it enumerates candidate implementations -- a single shift (x<<a), or a shift-op pair ((x<<a) + (x<<b) / (x<<a) - (x<<b)), or the fallback multiply -- VERIFIES each is 1:1 equal to x*C over many inputs, scores each by the measured cost model (mul > shift+add, per nx_measure_cost), and RETURNS the cheapest verified one. THIS is a building capability: the team discovers `x*7 = (x<<3)-x`, `x*9 = (x<<3)+x`, `x*1024 = x<<10` ITSELF -- I wrote the searcher; the search wrote the answers. It is the Generator leg the codegen loop consumes (each authored lowering is a verified, cheaper codegen rewrite). Refs: Warren, Hacker's Delight 2e ch.8 (strength reduction); the e-graph superopt idea (egg, Willsey POPL 2021).