Automatic Linear Resource Bound Analysis for Rust via Prophecy Potentials

Rust has become a popular system programming language that strikes a balance between memory safety and performance. Rust’s type system ensures the safety of low-level memory controls; however, a well-typed Rust program is not guaranteed to enjoy high performance. This article studies static analysis for resource consumption of Rust programs, aiming at understanding the performance of Rust programs. Although there have been tons of studies on static resource analysis, exploiting Rust’s memory safety—especially the borrow mechanisms and their properties—to aid resource-bound analysis, remains unexplored. This article presents RaRust, a type-based linear resource-bound analysis for well-typed Rust programs. RaRust follows the methodology of automatic amortized resource analysis (AARA) to build a resource-aware type system. To support Rust’s borrow mechanisms, including shared and mutable borrows, RaRust introduces shared and novel prophecy potentials to reason about borrows compositionally. To prove the soundness of RaRust, this article proposes Resource-Aware Borrow Calculus (RABC) as a variant of recently proposed Low-Level Borrow Calculus (LLBC). The experimental evaluation of a prototype implementation of RaRust demonstrates that RaRust is capable of inferring symbolic linear resource bounds for Rust programs featuring shared and mutable borrows, reborrows, heap-allocated data structures, loops, and recursion.