transforms: Allow to pass a pattern rewriter in CSE

Without passing the pattern rewriter, CSE couldn't be called inside
a pattern rewriter walker, as it would not notify the operations that
were deleted or replaced.

xdsl/transforms/canonicalization_patterns/stencil.py

@@ -41,7 +41,7 @@ def match_and_rewrite(self, op: stencil.ApplyOp, rewriter: PatternRewriter) -> N
                 continue
             a.replace_by(bbargs[rbargs[i]])
 
-        cse(op.region.block)
+        cse(op.region.block, rewriter)
 
 
 class ApplyUnusedOperands(RewritePattern):

xdsl/transforms/common_subexpression_elimination.py

@@ -5,6 +5,7 @@
 from xdsl.dialects.builtin import ModuleOp, UnregisteredOp
 from xdsl.ir import Block, Operation, Region, Use
 from xdsl.passes import ModulePass
+from xdsl.pattern_rewriter import PatternRewriter
 from xdsl.rewriter import Rewriter
 from xdsl.traits import (
     IsolatedFromAbove,
@@ -115,19 +116,15 @@ def has_other_side_effecting_op_in_between(
     return False
 
 
+@dataclass
 class CSEDriver:
     """
     Boilerplate class to handle and carry the state for CSE.
     """
 
-    _rewriter: Rewriter
+    _rewriter: Rewriter | PatternRewriter = field(default_factory=Rewriter)
     _to_erase: set[Operation] = field(default_factory=set)
-    _known_ops: KnownOps = KnownOps()
-
-    def __init__(self):
-        self._rewriter = Rewriter()
-        self._to_erase = set()
-        self._known_ops = KnownOps()
+    _known_ops: KnownOps = field(default_factory=KnownOps)
 
     def _mark_erasure(self, op: Operation):
         self._to_erase.add(op)
@@ -250,8 +247,11 @@ def simplify(self, thing: Operation | Block | Region):
         self._commit_erasures()
 
 
-def cse(thing: Operation | Block | Region):
-    CSEDriver().simplify(thing)
+def cse(thing: Operation | Block | Region, rewriter: PatternRewriter | None = None):
+    if rewriter is not None:
+        CSEDriver(_rewriter=rewriter).simplify(thing)
+    else:
+        CSEDriver().simplify(thing)
 
 
 class CommonSubexpressionElimination(ModulePass):

xdsl/transforms/control_flow_hoist.py

@@ -57,7 +57,7 @@ def match_and_rewrite(self, op: affine.IfOp, rewriter: PatternRewriter):
             return
         block = op.parent
         if block:
-            cse(block)
+            cse(block, rewriter)
 
 
 class SCFIfHoistPattern(RewritePattern):
@@ -84,7 +84,7 @@ def match_and_rewrite(self, op: scf.IfOp, rewriter: PatternRewriter):
         block = op.parent
         if block:
             # If we hoisted some ops, run CSE on that block to not keep pushing duplicates upward.
-            cse(block)
+            cse(block, rewriter)
 
 
 class ControlFlowHoistPass(ModulePass):