Certifying cost annotations in compilers

TL;DR

This paper introduces a labelling approach for building compilers that can reliably lift execution cost information from object code to source code, demonstrating its effectiveness through formal analysis and practical implementation.

Contribution

It proposes a novel labelling method for cost annotations in compilers, emphasizing compositionality, soundness, and scalability, validated by formal study and prototype implementation.

Findings

Labelling approach shows good compositionality.

Formal analysis supports soundness and precision.

Successful implementation on a C compiler fragment.

Abstract

We discuss the problem of building a compiler which can lift in a provably correct way pieces of information on the execution cost of the object code to cost annotations on the source code. To this end, we need a clear and flexible picture of: (i) the meaning of cost annotations, (ii) the method to prove them sound and precise, and (iii) the way such proofs can be composed. We propose a so-called labelling approach to these three questions. As a first step, we examine its application to a toy compiler. This formal study suggests that the labelling approach has good compositionality and scalability properties. In order to provide further evidence for this claim, we report our successful experience in implementing and testing the labelling approach on top of a prototype compiler written in OCAML for (a large fragment of) the C language.