[Mlir-commits] [mlir] [MLIR][Python] Add bindings for PDL constraint function registering (PR #160520)

[Maksim Levental]

================
@@ -153,12 +153,43 @@ def rew():
                 )
                 pdl.ReplaceOp(op0, with_op=newOp)
 
+        @pdl.pattern(benefit=1, sym_name="myint_add_zero_fold")
+        def pat():
+            t = pdl.TypeOp(i32)
+            v0 = pdl.OperandOp()
+            v1 = pdl.OperandOp()
+            v = pdl.apply_native_constraint([pdl.ValueType.get()], "has_zero", [v0, v1])
+            op0 = pdl.OperationOp(name="myint.add", args=[v0, v1], types=[t])
+
+            @pdl.rewrite()
+            def rew():
+                pdl.ReplaceOp(op0, with_values=[v])
+
     def add_fold(rewriter, results, values):
         a0, a1 = values
         results.append(IntegerAttr.get(i32, a0.value + a1.value))
 
+    def is_zero(value):
+        op = value.owner
+        if isinstance(op, Operation):
+            return op.name == "myint.constant" and op.attributes["value"].value == 0
+        return False
+
+    # Check if either operand is a constant zero,
+    # and append the other operand to the results if so.
+    def has_zero(rewriter, results, values):
+        v0, v1 = values
+        if is_zero(v0):
+            results.append(v1)
+            return False
+        if is_zero(v1):
+            results.append(v0)
----------------
makslevental wrote:

Sorry I haven't used this pdl API before: are results used for anything? Are they meant to be? Because I'm pretty sure currently (the current state of the PR) they're not and it'd be impossible to make it work (since you're wrapping in a `std:: vector`)?

https://github.com/llvm/llvm-project/pull/160520