Preparation for adding support for tiling to parallel loops.
Unit tests: pass. 62414 tests passed, 0 failed and 839 were skipped.
Glanced over quickly, looks innocuous enough to me an a good step towards allow generalization to affine, various ploops (affine or not).
If all tests pass (i.e. the check-mlir target), then go for it, we'll adapt if any issues comes up.
Thanks for doing this generalization effort.