More readable DaphneIR: split/combine of vectorized pipelines

In GitLab by @pdamme on Mar 8, 2022, 17:58

For a vectorized pipeline (VectorizedPipelineOp), both the way the inputs and split and the way the outputs are combined are represented by enums (see src/ir/daphneir/DaphneVectorizableOpInterface.td, VectorSplitAttr/VectorCombineAttr). When printing the IR, these are displayed as integers. To make the IR more readable, it would be great to display actual words.

For instance, instead of:

'Reference to deleted milestone 12' = "daphne.vectorizedPipeline"(...) ( {...},  {...}) {combines = [1], ..., splits = [1, 1]} : (...) -> ...

it should print something like:

'Reference to deleted milestone 12' = "daphne.vectorizedPipeline"(...) ( {...},  {...}) {combines = [rows], ..., splits = [rows, rows]} : (...) -> ...

Some useful documentation can be found at:

• https://mlir.llvm.org/docs/OpDefinitions/#custom-parser-and-printer-methods
• https://mlir.llvm.org/docs/OpDefinitions/#declarative-assembly-format