[Test] add two test_is_linear variants

tests/test_is_linear.py

+import onnx.helper as oh
+from onnx import TensorProto
+
+import finn.analysis.topology as ta
+import finn.transformation.infer_shapes as si
+from finn.core.modelwrapper import ModelWrapper
+
+
+def test_is_linear_linear():
+    top_in = oh.make_tensor_value_info("top_in", TensorProto.FLOAT, [2])
+    add_param = oh.make_tensor_value_info("add_param", TensorProto.FLOAT, [2])
+    mul_param = oh.make_tensor_value_info("mul_param", TensorProto.FLOAT, [2])
+    top_out = oh.make_tensor_value_info("top_out", TensorProto.FLOAT, [2])
+    modelproto = oh.make_model(
+        oh.make_graph(
+            name="test",
+            inputs=[top_in],
+            outputs=[top_out],
+            value_info=[add_param, mul_param],
+            nodes=[
+                oh.make_node("Add", ["top_in", "add_param"], ["middle"]),
+                oh.make_node("Mul", ["middle", "mul_param"], ["top_out"]),
+            ],
+        )
+    )
+    model = ModelWrapper(modelproto)
+    model = model.transform_single(si.infer_shapes)
+    ret = model.analysis(ta.is_linear)
+    assert ret["is_linear"] is True
+
+
+def test_is_linear_forked_node_output():
+    top_in = oh.make_tensor_value_info("top_in", TensorProto.FLOAT, [2])
+    add_param = oh.make_tensor_value_info("add_param", TensorProto.FLOAT, [2])
+    mul0_param = oh.make_tensor_value_info("mul0_param", TensorProto.FLOAT, [2])
+    mul1_param = oh.make_tensor_value_info("mul1_param", TensorProto.FLOAT, [2])
+    mul0_res = oh.make_tensor_value_info("mul0_res", TensorProto.FLOAT, [2])
+    mul1_res = oh.make_tensor_value_info("mul1_res", TensorProto.FLOAT, [2])
+    top_out = oh.make_tensor_value_info("top_out", TensorProto.FLOAT, [2])
+    modelproto = oh.make_model(
+        oh.make_graph(
+            name="test",
+            inputs=[top_in],
+            outputs=[top_out],
+            value_info=[add_param, mul0_param, mul1_param, mul0_res, mul1_res],
+            nodes=[
+                oh.make_node("Add", ["top_in", "add_param"], ["middle"]),
+                oh.make_node("Mul", ["middle", "mul0_param"], ["mul0_res"]),
+                oh.make_node("Mul", ["middle", "mul1_param"], ["mul1_res"]),
+                oh.make_node("Add", ["mul0_res", "mul1_res"], ["top_out"]),
+            ],
+        )
+    )
+    model = ModelWrapper(modelproto)
+    model = model.transform_single(si.infer_shapes)
+    ret = model.analysis(ta.is_linear)
+    assert ret["is_linear"] is False