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This includes the rename from `mlirOpRewritePattenCreate` to `mlirOpRewritePatternCreate` in CAPI, and other typo fixes in docs and code comments.
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This is a follow-up PR of #162699.
In this PR we clean CAPI and Python bindings of MLIR rewrite part by:
- remove all manually-defined `wrap`/`unwrap` functions;
- remove useless nanobind-defined Python class `RewritePattern`.
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This PR adds support for defining custom **`RewritePattern`**
implementations directly in the Python bindings.
Previously, users could define similar patterns using the PDL dialect’s
bindings. However, for more complex patterns, this often required
writing multiple Python callbacks as PDL native constraints or rewrite
functions, which made the overall logic less intuitive—though it could
be more performant than a pure Python implementation (especially for
simple patterns).
With this change, we introduce an additional, straightforward way to
define patterns purely in Python, complementing the existing PDL-based
approach.
### Example
```python
def to_muli(op, rewriter):
with rewriter.ip:
new_op = arith.muli(op.operands[0], op.operands[1], loc=op.location)
rewriter.replace_op(op, new_op.owner)
with Context():
patterns = RewritePatternSet()
patterns.add(arith.AddIOp, to_muli) # a pattern that rewrites arith.addi to arith.muli
frozen = patterns.freeze()
module = ...
apply_patterns_and_fold_greedily(module, frozen)
```
---------
Co-authored-by: Maksim Levental <maksim.levental@gmail.com>
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In [#160520](https://github.com/llvm/llvm-project/pull/160520), we
discussed the current limitations of PDL rewriting in Python (see [this
comment](https://github.com/llvm/llvm-project/pull/160520#issuecomment-3332326184)).
At the moment, we cannot create new operations in PDL native (python)
rewrite functions because the `PatternRewriter` APIs are not exposed.
This PR introduces bindings to retrieve the insertion point of the
`PatternRewriter`, enabling users to create new operations within Python
rewrite functions. With this capability, more complex rewrites e.g. with
branching and loops that involve op creations become possible.
---------
Co-authored-by: Maksim Levental <maksim.levental@gmail.com>
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This is a follow-up to #159926.
That PR (#159926) exposed native rewrite function registration in PDL
through the C API and Python, enabling use with
`pdl.apply_native_rewrite`.
In this PR, we add support for native constraint functions in PDL via
`pdl.apply_native_constraint`, further completing the PDL API.
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(#159926)
In the MLIR Python bindings, we can currently use PDL to define simple
patterns and then execute them with the greedy rewrite driver. However,
when dealing with more complex patterns—such as constant folding for
integer addition—we find that we need `apply_native_rewrite` to actually
perform arithmetic (i.e., compute the sum of two constants). For
example, consider the following PDL pseudocode:
```mlir
pdl.pattern : benefit(1) {
%a0 = pdl.attribute
%a1 = pdl.attribute
%c0 = pdl.operation "arith.constant" {value = %a0}
%c1 = pdl.operation "arith.constant" {value = %a1}
%op = pdl.operation "arith.addi"(%c0, %c1)
%sum = pdl.apply_native_rewrite "addIntegers"(%a0, %a1)
%new_cst = pdl.operation "arith.constant" {value = %sum}
pdl.replace %op with %new_cst
}
```
Here, `addIntegers` cannot be expressed in PDL alone—it requires a
*native rewrite function*. This PR introduces a mechanism to support
exactly that, allowing complex rewrite patterns to be expressed in
Python and enabling many passes to be implemented directly in Python as
well.
As a test case, we defined two new operations (`myint.constant` and
`myint.add`) in Python and implemented a constant-folding rewrite
pattern for them. The core code looks like this:
```python
m = Module.create()
with InsertionPoint(m.body):
@pdl.pattern(benefit=1, sym_name="myint_add_fold")
def pat():
...
op0 = pdl.OperationOp(name="myint.add", args=[v0, v1], types=[t])
@pdl.rewrite()
def rew():
sum = pdl.apply_native_rewrite(
[pdl.AttributeType.get()], "add_fold", [a0, a1]
)
newOp = pdl.OperationOp(
name="myint.constant", attributes={"value": sum}, types=[t]
)
pdl.ReplaceOp(op0, with_op=newOp)
def add_fold(rewriter, results, values):
a0, a1 = values
results.push_back(IntegerAttr.get(i32, a0.value + a1.value))
pdl_module = PDLModule(m)
pdl_module.register_rewrite_function("add_fold", add_fold)
```
The idea is previously discussed in Discord #mlir-python channel with
@makslevental.
---------
Co-authored-by: Maksim Levental <maksim.levental@gmail.com>
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(#157487)
In https://github.com/llvm/llvm-project/pull/94714, we add a python
function `apply_patterns_and_fold_greedily` which accepts an
`MlirModule` as the argument type. However, sometimes we want to apply
patterns with an `MlirOperation` argument, and there is currently no
python API to convert an `MlirOperation` to `MlirModule`.
So here we overload this function `apply_patterns_and_fold_greedily` to
do this (also a corresponding new C API
`mlirApplyPatternsAndFoldGreedilyWithOp`)
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I observed that we have the boundary comments in the codebase like:
```
//===----------------------------------------------------------------------===//
// ...
//===----------------------------------------------------------------------===//
```
I also observed that there are incomplete boundary comments. The
revision is generated by a script that completes the boundary comments.
```
//===----------------------------------------------------------------------===//
// ...
...
```
Signed-off-by: hanhanW <hanhan0912@gmail.com>
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The greedy rewriter is used in many different flows and it has a lot of
convenience (work list management, debugging actions, tracing, etc). But
it combines two kinds of greedy behavior 1) how ops are matched, 2)
folding wherever it can.
These are independent forms of greedy and leads to inefficiency. E.g.,
cases where one need to create different phases in lowering and is
required to applying patterns in specific order split across different
passes. Using the driver one ends up needlessly retrying folding/having
multiple rounds of folding attempts, where one final run would have
sufficed.
Of course folks can locally avoid this behavior by just building their
own, but this is also a common requested feature that folks keep on
working around locally in suboptimal ways.
For downstream users, there should be no behavioral change. Updating
from the deprecated should just be a find and replace (e.g., `find ./
-type f -exec sed -i
's|applyPatternsAndFoldGreedily|applyPatternsGreedily|g' {} \;` variety)
as the API arguments hasn't changed between the two.
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This exposes most of the `RewriterBase` methods to the C API.
This allows to manipulate both the `IRRewriter` and the
`PatternRewriter`. The
`IRRewriter` can be created from the C API, while the `PatternRewriter`
cannot.
The missing operations are the ones taking `Block::iterator` and
`Region::iterator` as
parameters, as they are not exposed by the C API yet AFAIK.
The Python bindings for these methods and classes are not implemented.
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Following a rather direct approach to expose PDL usage from C and then
Python. This doesn't yes plumb through adding support for custom
matchers through this interface, so constrained to basics initially.
This also exposes greedy rewrite driver. Only way currently to define
patterns is via PDL (just to keep small). The creation of the PDL
pattern module could be improved to avoid folks potentially accessing
the module used to construct it post construction. No ergonomic work
done yet.
---------
Signed-off-by: Jacques Pienaar <jpienaar@google.com>
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