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Vadim Zaliva, Ilia Zaichuk and Franz Franchetti (Proc. Working Conference on Verified Software: Theories, Tools, and Experiments (VSTTE), 2020)
Verified Translation Between Purely Functional and Imperative Domain Specific Languages in HELIX
Published paper (link to publisher)
HELIX is a formally verified language and rewriting engine for generation of high-performance implementation for a variety of numerical algorithms. Based on the existing SPIRAL system, HELIX adds the rigor of formal verification of its correctness using the Coq proof assistant. It formally defines a series of domain-specific languages starting with HCOL, which represents a computation data flow. HELIX works by transforming the original program through a series of intermediate languages, culminating in LLVM IR. In this paper, we will focus on three intermediate languages and the formally verified translation between them. Translation between these three languages is non-trivial, because each subsequent language introduces lower-level abstractions, compared to the previous one. During these steps, we switch from pure-functional language using mixed embedding to a deep-embedded imperative one, also introducing a memory model, lexical scoping, monadic error handling, and transition from abstract algebraic datatype to floatingpoint-numbers. We will demonstrate the design of these languages, the automatic reification between them, and automated proofs of semantic preservation, in Coq.Keywords: Coq, Verification, HELIX, Domain-specific