llvm-project

6740d701 - [mlir][Linalg] Deprecate `linalg::tileToForallOp` and `linalg::tileToForallOpUsingTileSizes` (#91878)

[mlir][Linalg] Deprecate `linalg::tileToForallOp` and `linalg::tileToForallOpUsingTileSizes` (#91878) The implementation of these methods are legacy and they are removed in favor of using the `scf::tileUsingSCF` methods as replacements. To get the latter on par with requirements of the deprecated methods, the tiling allows one to specify the maximum number of tiles to use instead of specifying the tile sizes. When tiling to `scf.forall` this specification is used to generate the `num_threads` version of the operation. A slight deviation from previous implementation is that the deprecated method always generated the `num_threads` variant of the `scf.forall` operation. Instead now this is driven by the tiling options specified. This reduces the indexing math generated when the tile sizes are specified. **Moving from `linalg::tileToForallOp` to `scf::tileUsingSCF`** ``` OpBuilder b; TilingInterface op; ArrayRef<OpFoldResult> numThreads; ArrayAttr mapping; FailureOr<ForallTilingResult> result =linalg::tileToForallOp(b, op, numThreads, mapping); ``` can be replaced by ``` scf::SCFTilingOptions options; options.setNumThreads(numThreads); options.setLoopType(scf::SCFTilingOptions::LoopType::ForallOp); options.setMapping(mapping.getValue()); /*note the difference that setMapping takes an ArrayRef<Attribute> */ FailureOr<scf::SCFTilingResult> result = scf::tileUsingSCF(b, op, options); ``` This generates the `numThreads` version of the `scf.forall` for the inter-tile loops, i.e. ``` ... = scf.forall (%arg0, %arg1) in (%nt0, %nt1) shared_outs(...) ``` **Moving from `linalg::tileToForallOpUsingTileSizes` to `scf::tileUsingSCF`** ``` OpBuilder b; TilingInterface op; ArrayRef<OpFoldResult> tileSizes; ArrayAttr mapping; FailureOr<ForallTilingResult> result =linalg::tileToForallOpUsingTileSizes(b, op, tileSizes, mapping); ``` can be replaced by ``` scf::SCFTilingOptions options; options.setTileSizes(tileSizes); options.setLoopType(scf::SCFTilingOptions::LoopType::ForallOp); options.setMapping(mapping.getValue()); /*note the difference that setMapping takes an ArrayRef<Attribute> */ FailureOr<scf::SCFTilingResult> result = scf::tileUsingSCF(b, op, options); ``` Also note that `linalg::tileToForallOpUsingTileSizes` would effectively call the `linalg::tileToForallOp` by computing the `numThreads` from the `op` and `tileSizes` and generate the `numThreads` version of the `scf.forall`. That is not the case anymore. Instead this will directly generate the `tileSizes` version of the `scf.forall` op ``` ... = scf.forall(%arg0, %arg1) = (%lb0, %lb1) to (%ub0, %ub1) step(%step0, %step1) shared_outs(...) ``` If you actually want to use the `numThreads` version, it is upto the caller to compute the `numThreads` and set `options.setNumThreads` instead of `options.setTileSizes`. Note that there is a slight difference in the num threads version and tile size version. The former requires an additional `affine.max` on the tile size to ensure non-negative tile sizes. When lowering to `numThreads` version this `affine.max` is not needed since by construction the tile sizes are non-negative. In previous implementations, the `numThreads` version generated when using the `linalg::tileToForallOpUsingTileSizes` method would avoid generating the `affine.max` operation. To get the same state, downstream users will have to additionally normalize the `scf.forall` operation. **Changes to `transform.structured.tile_using_forall`** The transform dialect op that called into `linalg::tileToForallOp` and `linalg::tileToForallOpUsingTileSizes` have been modified to call `scf::tileUsingSCF`. The transform dialect op always generates the `numThreads` version of the `scf.forall` op. So when `tile_sizes` are specified for the transform dialect op, first the `tile_sizes` version of the `scf.forall` is generated by the `scf::tileUsingSCF` method which is then further normalized to get back to the same state. So there is no functional change to `transform.structured.tile_using_forall`. It always generates the `numThreads` version of the `scf.forall` op (as it did before this change). --------- Signed-off-by: MaheshRavishankar <mahesh.ravishankar@gmail.com>