Users of proprietary and/or legacy programs without vendor support are denied the significant advances in compiler technologies of the past decades. Adapting these technologies to operate directly on binaries without source code is often infeasible. Binary recompilers attempt to bridge this gap by "lifting" binary executables to compiler-level intermediate representations (IR) and "lowering" them back down to executable form, enabling application of the full range of analyses and transformations available in modern compiler infrastructures. Past approaches could not recover local variables in lifted programs with sufficient precision, which is a necessary prerequisite for many compiler-related applications, including performance optimization. They have relied on heuristics failing on certain input programs, or on conservative over-approximations yielding imprecise results.

The maintenance of software distributed in its binary form can become challenging over time, due to the lack of vendor support or obsolete build environments. This can be costly when dealing with critical security vulnerabilities that are difficult to fix on a binary level. Moreover, advances in compiler technologies of the past decades remain unavailable to the users of such legacy binaries for performing optimizations and transformations. Binary recompilers aim to bridge this divide by "lifting" binary executables to compiler-level intermediate representations (IR) and "lowering" them back again. But, current recompilers fail on that promise as they rely on unsound heuristics or impose high tracing overheads. Crucially, no existing recompiler addresses the specific challenges imposed by multithreaded programs that are ubiquitous in the modern software space.