TF frontend: add expm1 op (apache#6783)

* TF frontend: add expm1 op

* TF frontend: add description for expm1

* TF frontend: use overload operator - instead of subtract

* TF frontend: Limits the range of input data in the Expm1 test

Co-authored-by: xup <xp224797@alibaba-inc.com>

python/tvm/relay/frontend/tensorflow.py

@@ -788,6 +788,15 @@ def _impl(inputs, attr, params, mod):
     return _impl
 
 
+def _expm1():
+    # op description: https://www.tensorflow.org/api_docs/python/tf/math/expm1
+    def _impl(inputs, attr, params, mod):
+        exp_out = get_relay_op("exp")(inputs[0])
+        return exp_out - tvm.relay.const(1.0)
+
+    return _impl
+
+
 def _resize(method):
     def _impl(inputs, attr, params, mod):
         if attr["_output_shapes"][0] is not None:
@@ -2297,6 +2306,7 @@ def _impl(inputs, attr, params, mod):
     "EuclideanNorm": _euclidean_norm(),
     "Exp": AttrCvt("exp"),
     "ExpandDims": _expand_dims(),
+    "Expm1": _expm1(),
     "Fill": _fill(),
     "Floor": AttrCvt("floor"),
     "FloorDiv": _floordiv(),

tests/python/frontend/tensorflow/test_forward.py

@@ -3504,6 +3504,22 @@ def test_forward_atan2():
     compare_tf_with_tvm([np_data_1, np_data_2], ["in_data_1:0", "in_data_2:0"], "atan2:0")
 
 
+def test_forward_expm1():
+    """test operator expm1 """
+
+    def _test_forward_expm1(shape):
+        tf.disable_eager_execution()
+        np_data = np.random.uniform(1, 10, size=shape).astype(np.float32)
+        tf.reset_default_graph()
+        in_data = tf.placeholder(tf.float32, shape, name="in_data")
+        tf.expm1(in_data, name="expm1")
+        compare_tf_with_tvm([np_data], ["in_data:0"], "expm1:0")
+
+    _test_forward_expm1([1, 100])
+    _test_forward_expm1([1, 10, 10])
+    _test_forward_expm1([2, 5, 2, 5])
+
+
 def test_forward_negative():
     """test tf operator Neg """
     np_data = np.random.uniform(-100, 255, size=(224, 224, 3)).astype(np.float32)