[MLIR][Transform][Tune] Introduce transform.tune.alternatives op (#160724)

This op enables expressing uncertainty regarding what should be
happening at particular places in transform-dialect schedules. In
particular, it enables representing a choice among alternative regions.
This choice is resolved through providing a `selected_region` argument.
When this argument is provided, the semantics are such that it is valid
to rewrite the op through substituting in the selected region -- with
the op's interpreted semantics corresponding to exactly this.

This op represents another piece of the puzzle w.r.t. a toolkit for
expressing autotuning problems with the transform dialect. Note that
this goes beyond tuning knobs _on_ transforms, going further by making
it tunable which (sequences of) transforms are to be applied.

Author: Rolf Morel

mlir/python/mlir/dialects/transform/tune.py

@@ -6,6 +6,9 @@
 
 from ...ir import (
     Type,
+    Value,
+    Operation,
+    OpView,
     Attribute,
     ArrayAttr,
     StringAttr,
@@ -19,7 +22,10 @@
 from .._transform_tune_extension_ops_gen import _Dialect
 
 try:
-    from .._ods_common import _cext as _ods_cext
+    from .._ods_common import (
+        get_op_result_or_value as _get_op_result_or_value,
+        _cext as _ods_cext,
+    )
 except ImportError as e:
     raise RuntimeError("Error loading imports from extension module") from e
 
@@ -36,7 +42,7 @@ def __init__(
             ArrayAttr, Sequence[Union[Attribute, bool, int, float, str]], Attribute
         ],
         *,
-        selected: Optional[Attribute] = None,
+        selected: Optional[Union[Attribute, bool, int, float, str]] = None,
         loc=None,
         ip=None,
     ):
@@ -75,8 +81,62 @@ def knob(
         ArrayAttr, Sequence[Union[Attribute, bool, int, float, str]], Attribute
     ],
     *,
-    selected: Optional[Attribute] = None,
+    selected: Optional[Union[Attribute, bool, int, float, str]] = None,
     loc=None,
     ip=None,
 ):
     return KnobOp(result, name, options, selected=selected, loc=loc, ip=ip)
+
+
+@_ods_cext.register_operation(_Dialect, replace=True)
+class AlternativesOp(AlternativesOp):
+    def __init__(
+        self,
+        results: Sequence[Type],
+        name: Union[StringAttr, str],
+        num_alternatives: int,
+        *,
+        selected_region: Optional[
+            Union[int, IntegerAttr, Value, Operation, OpView]
+        ] = None,
+        loc=None,
+        ip=None,
+    ):
+        if isinstance(name, str):
+            name = StringAttr.get(name)
+
+        selected_region_attr = selected_region_param = None
+        if isinstance(selected_region, IntegerAttr):
+            selected_region_attr = selected_region
+        elif isinstance(selected_region, int):
+            selected_region_attr = IntegerAttr.get(
+                IntegerType.get_signless(32), selected_region
+            )
+        elif isinstance(selected_region, (Value, Operation, OpView)):
+            selected_region_param = _get_op_result_or_value(selected_region)
+
+        super().__init__(
+            results,
+            name,
+            num_alternatives,
+            selected_region_attr=selected_region_attr,
+            selected_region_param=selected_region_param,
+            loc=loc,
+            ip=ip,
+        )
+        for region in self.regions:
+            region.blocks.append()
+
+
+def alternatives(
+    results: Sequence[Type],
+    name: Union[StringAttr, str],
+    num_alternatives: int,
+    *,
+    selected_region: Optional[Union[int, IntegerAttr, Value, Operation, OpView]] = None,
+    loc=None,
+    ip=None,
+):
+    return AlternativesOp(
+        results, name, num_alternatives, selected_region=selected_region, loc=loc, ip=ip
+    )