[mlir] Add python test for shape dialect

[jpienaar]

Summary

Add basic test for shape.const_shape op as start.

mlir/test/python/dialects/shape.py

+# RUN: %PYTHON %s | FileCheck %s
+
+from mlir.ir import *
+import numpy as np
+import mlir.dialects.builtin as builtin
+import mlir.dialects.shape as shape
+
+
+def run(f):
+  print("\nTEST:", f.__name__)
+  f()
+  return f
+
+
+# CHECK-LABEL: TEST: testConstShape
+@run
+def testConstShape():
+  with Context() as ctx, Location.unknown():
+    module = Module.create()
+    f32 = F32Type.get()
+    indexT = IndexType.get()
+    with InsertionPoint(module.body):
+      @builtin.FuncOp.from_py_func(
+          RankedTensorType.get((12, -1), f32))
+      def const_shape_tensor(arg):
+        return shape.ConstShapeOp(RankedTensorType.get((2,), indexT),
+                                  DenseElementsAttr.get(np.array([10, 20])))
+
+    # CHECK-LABEL: func @const_shape_tensor(%arg0: tensor<12x?xf32>)
+    # CHECK: shape.const_shape [10, 20] : tensor<2xindex>
+    print(module)
+