Overall Objectives
New Software and Platforms
New Results
Partnerships and Cooperations
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Section: New Results

Mechanical Verification of SSA-based Compilation Techniques

Participants : Delphine Demange, Yon Fernandez de Retana, David Pichardie.

We have continued our work on the mechanical verification of SSA-based compilation techniques  [30], [31], [36].

A crucial phase for efficient machine code generation is the destruction of a middle-end SSA-like IR. To this end, we have studied a variant of SSA, namely the Conventional SSA form, which simplifies the destruction back to non-SSA code (i.e. at the exit point of the middle-end). This had long remained a difficult problem, even in a non-verified environment. We formally defined and proved the properties of the generation of Conventional SSA. Finally, we implemented and proved correct a coalescing destruction of the Conventional SSA form, à la Boissinot et al.  [33], where variables can be coalesced according to a refined notion of interference. Our CSSA-based, coalescing destruction allows us to coalesce more than 99% of introduced copies, on average, and leads to encouraging results concerning spilling and reloading during post-SSA allocation. This work has been published in [24].