[llvm] [mlir] [mlir] Add PDL C & Python usage (PR #94714)

[Maksim Levental via llvm-commits]

================
@@ -0,0 +1,67 @@
+# RUN: %PYTHON %s 2>&1 | FileCheck %s
+
+from mlir.dialects import arith, func, pdl
+from mlir.dialects.builtin import module
+from mlir.ir import *
+from mlir.rewrite import *
+
+
+def construct_and_print_in_module(f):
+    print("\nTEST:", f.__name__)
+    with Context(), Location.unknown():
+        module = Module.create()
+        with InsertionPoint(module.body):
+            module = f(module)
+        if module is not None:
+            print(module)
+    return f
+
+
+# CHECK-LABEL: TEST: test_add_to_mul
+# CHECK: arith.muli
+ at construct_and_print_in_module
+def test_add_to_mul(module_):
+    index_type = IndexType.get()
+
+    # Create a test case.
+    @module(sym_name="ir")
+    def ir():
+        @func.func(index_type, index_type)
+        def add_func(a, b):
+            return arith.addi(a, b)
+
+    # Create a rewrite from add to mul. This will match
+    # - operation name is arith.addi
+    # - operands are index types.
+    # - there are two operands.
+    with Location.unknown():
+        m = Module.create()
+        with InsertionPoint(m.body):
+            # Change all arith.addi with index types to arith.muli.
+            pattern = pdl.PatternOp(1, "addi_to_mul")
+            with InsertionPoint(pattern.body):
----------------
makslevental wrote:

```suggestion
            @pd.pattern(1, "addi_to_mul")
            def pat():
```

https://github.com/llvm/llvm-project/pull/94714