Verifying Fast and Sparse SSA-Based Optimizations in Coq

8 years 9 days ago

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The Static Single Assignment (SSA) form is a predominant technology in modern compilers, enabling powerful and fast program optimizations. Despite its great success in the implementation of production compilers, it is only very recently that this technique has been introduced in veriﬁed compilers. As of today, few evidence exist on that, in this context, it also allows faster and simpler optimizations. This work builds on the CompCertSSA veriﬁed compiler (an SSA branch of the veriﬁed CompCert C compiler). We implement and verify two prevailing SSA optimizations: Sparse Conditional Constant Propagation and Global Value Numbering. For both transformations, we mechanically prove their soundness in the Coq proof assistant. Both optimization proofs are embedded in a single sparse optimization framework, factoring out many of the dominance-based reasoning steps required in proofs of SSA-based optimizations. Our experimental evaluations indicate both a better precision, and a signiﬁca...

Delphine Demange, David Pichardie, Léo Stef

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