Section: New Results

Real-time systems compilation

Participants : Dumitru Potop Butucaru, Keryan Didier, Mihail Asavoae.

This research line develops over various results of the team over the years, its aim being to develop fully automatic implementation flows going fully automatically from functional and non-functional specification to correct and efficient running implementation. We advocate for a real-time systems compilation approach that combines aspects of both real-time scheduling and compilation of both classical and synchronous languages. Like a classical compiler such as GCC, a real-time systems compiler should use fast and efficient scheduling and code generation heuristics, to ensure scalability. Similarly, it should provide traceability support under the form of informative error messages enabling an incremental trial-and-error design style, much like that of classical application software. This is more difficult than in a classical compiler, given the complexity of the transformation flow (creation of tasks, allocation, scheduling, synthesis of communication and synchronization code, etc.), and requires a full formal integration along the whole flow, including the crucial issue of correct hardware abstraction. A real-time systems compiler should perform precise, conservative timing accounting along the whole scheduling and code generation flow, allowing it to produce safe and tight real-time guarantees. More generally, and unlike in classical compilers, the allocation and scheduling algorithms must take into account a variety of non-functional requirements, such as real-time constraints, criticality, partitioning, preemptability, allocation constraints, etc. As the accent is put on the respect of requirements (as opposed to optimization of a metric, like in classical compilation), resulting scheduling problems are quite different.

We are currently building such a real-time systems compiler, called Lopht. The construction of the Lopht tool, which takes into account complex functional and non-functional specifications is discussed in the corresponding section and in [17] .

This year, we have initiated work on two fundamental topics. The first one is sound architecture abstraction – ensuring that the platform models used for real-time scheduling and code generation are conservative abstractions of the real hardware and basic software, allowing the generation of implementations that are functionally and non-functionally correct. This work is performed in the framework of the LEOC Capacites project, which funds the post-doc of Mihail Asavoae. The second line of work aims at formally proving that the output of Lopht is correct with respect to its input models (including functional specification and platform model). This work is performed in the ITEA3 Assume project, which funds the PhD thesis of Keryan Didier. Together with the Parkas team-project we have also considered the implementation of mixed-criticality systems [26] .