[RFC][MLIR] OpenMP Loop Transformation : tile and unroll directive operation support for omp.dialect

[ftynse]

@kiranchandramohan

I did not fully understand this point. From your original proposal, the attributes are always on the OpenMP dialect operations. For the workshare-loop it is on omp.wsloop, and so is it for the omp.transform_loop standalone operation. There are no foreign-dialect attributes here.

My proposal didn’t have omp.transform_loop, but that approach looks interesting.

@kiranchandramohan

When we discussed this before, there were some strong objections against the nested approach and there was a requirement that worksharing loop be represented as a loop. Some of it is captured in this comment . Would adding the OpenMPLoopInterface to the scf.for or fir.do_loop be sufficient to prevent transformations of these loops by other passes?

It wouldn’t. Generic passes are not required to check if an operation implements an interface, and are not even expected to know about dialect-specific interfaces. I am also not entirely convinced that having a different operation is sufficient by itself to prevent all transformations.

I am rather repulsed by the idea of giving omp.tile optional loop semantics just to prevent some transformations. Maybe we could have an omp.canonical_loop that matches the definition in the spec and have frontends emit that instead of scf.for / fir.do_loop (potentially via an internal transform before any other passes can run).