llvm-project

dbeda4f4 - [mlir][SCF] Add `scf::tileAndFuseConsumer` that tiles a consumer into a given tiled loop nest. (#167634)

[mlir][SCF] Add `scf::tileAndFuseConsumer` that tiles a consumer into a given tiled loop nest. (#167634) The existing `scf::tileAndFuseConsumerOfSlices` takes a list of slices (and loops they are part of), tries to find the consumer of these slices (all slices are expected to be the same consumer), and then tiles the consumer into the loop nest using the `TilingInterface`. A more natural way of doing consumer fusion is to just start from the consumer, look for operands that are produced by the loop nest passed in as `loops` (presumably these loops are generated by tiling, but that is not a requirement for consumer fusion). Using the consumer you can find the slices of the operands that are accessed within the loop which you can then use to tile and fuse the consumer (using `TilingInterface`). This handles more naturally the case where multiple operands of the consumer come from the loop nest. The `scf::tileAndFuseConsumerOfSlices` was implemented as a mirror of `scf::tileAndFuseProducerOfSlice`. For the latter, the slice has a single producer for the source of the slice, which makes it a natural way of specifying producer fusion. But for consumers, the result might have multiple users, resulting in multiple candidates for fusion, as well as a fusion candidate using multiple results from the tiled loop nest. This means using slices (`tensor.insert_slice`/`tensor.parallel_insert_slice`) as a hook for consumer fusion turns out to be quite hard to navigate. The use of the consumer directly avoids all those pain points. In time the `scf::tileAndFuseConsumerOfSlices` should be deprecated in favor of `scf::tileAndFuseConsumer`. There is a lot of tech-debt that has accumulated in `scf::tileAndFuseConsumerOfSlices` that needs to be cleanedup. So while that gets cleaned up, and required functionality is moved to `scf::tileAndFuseConsumer`, the old path is still maintained. The test for `scf::tileAndFuseConsumerUsingSlices` is copied to `tile-and-fuse-consumer.mlir` to `tile-and-fuse-consumer-using-slices.mlir`. All the tests that were there in this file are now using the `tileAndFuseConsumer` method. The test op `test.tile_and_fuse_consumer` is modified to call `scf::tileAndFuseConsumer`, while a new op `test.tile_and_fuse_consumer_of_slice` is used to keep the old path tested while it is deprecated. --------- Signed-off-by: MaheshRavishankar <mahesh.ravishankar@gmail.com>