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diff --git a/mlir/docs/Bindings/Python.md b/mlir/docs/Bindings/Python.md index 893c6d4..7e6a466a 100644 --- a/mlir/docs/Bindings/Python.md +++ b/mlir/docs/Bindings/Python.md @@ -1188,6 +1188,21 @@ which can be `import`ed from the main dialect file, i.e. `python/mlir/dialects/<dialect-namespace>/passes.py` if it is undesirable to make the passes available along with the dialect. +## Extending MLIR in Python + +The MLIR Python bindings provide support for defining custom components in Python, +mainly including dialects, passes, and rewrite patterns. +The following sections outline how each of these can be implemented. + +### Dialects + +Dialects can be defined through the IRDL dialect bindings in Python. +The IRDL bindings offer a `load_dialects` function that +converts an MLIR module containing `irdl.dialect` ops into MLIR dialects. +For further details, see the documentation of [the IRDL dialect](../Dialects/IRDL.md). + +### Passes + Passes can be defined as Python callables via the `PassManager.add` API. In such case, the callable is wrapped as an `mlir::Pass` internally and executed as part of the pass pipeline when `PassManager.run` is invoked. @@ -1209,6 +1224,44 @@ pm.add('some-cpp-defined-passes') pm.run(some_op) ``` +### Rewrite Patterns + +Rewrite patterns can be registered via the `add` method +of `mlir.rewrite.RewritePatternSet` in Python. +This method takes the operation type to be rewritten +and a Python callable that defines the *match and rewrite* logic. +Note that the Python callable should be defined so that +the rewrite is applied if and only if the match succeeds, +which corresponds to the return value being castable to `False`. + +The `RewritePatternSet` can be converted into +a `FrozenRewritePatternSet` using the `freeze` method, +which can be applied to an operation through +the greedy pattern driver using `apply_patterns_and_fold_greedily`. +The following example demonstrates the typical usage: + +```python +def to_muli(op, rewriter): + with rewriter.ip: + new_op = arith.muli(op.lhs, op.rhs, loc=op.location) + rewriter.replace_op(op, new_op) + +patterns = RewritePatternSet() +patterns.add(arith.AddIOp, to_muli) # Rewrite arith.addi into arith.muli +patterns.add(...) +frozen = patterns.freeze() + +module = ... +apply_patterns_and_fold_greedily(module, frozen) +``` + +The PDL dialect bindings also enable defining and generating rewrite patterns in Python. +The `mlir.rewrite.PDLModule` class accepts a module containing `pdl.pattern` ops, +which can be transformed into a `FrozenRewritePatternSet` using the `freeze` method. +This frozen set can then be applied to an operation +using the greedy rewrite pattern driver via `apply_patterns_and_fold_greedily`. +For further information, see [the PDL dialect documentation](/docs/Dialects/PDLOps/). + ### Other functionality Dialect functionality other than IR objects or passes, such as helper functions, |