[flang] [llvm] [OpenMP][Draft] Breaking up of combined/composite directives (PR #80059)

[Sergio Afonso via llvm-commits]

skatrak wrote:

One concern I have about the general approach is whether it makes sense to do this for both combined and composite constructs. For combined constructs I think it's clear this is useful, since each leaf construct can be lowered independently, so each of them would also get its applicable set of clauses.

However, composite constructs will have to be dealt with as a whole, rather than what we currently do (basically treat them as combined constructs during PFT to MLIR lowering). It looks like we might even be going to follow the route of representing each composite construct as its own MLIR operation, as per @kiranchandramohan's comments in #79843.

Having that in mind, would it make sense to, for the purposes of this patch, consider composite constructs as leaves themselves? That should probably reduce the number of cases where you'd have to insert new clauses or create some sort of higher-level representation, as discussed in yesterday's community call (hopefully to zero, removing the need for that). Then, during lowering of each composite construct we could look at these corner cases.

https://github.com/llvm/llvm-project/pull/80059