Allow fused ops to create outputs and set types/shapes in pre_validation (#3839)

* Allow fused ops to create outputs and set types/shapes in pre_validation

* style fix

src/ngraph/op/fused/lstm_cell.cpp

@@ -99,6 +99,11 @@ op::LSTMCell::LSTMCell(const Output<Node>& X,
 
 void op::LSTMCell::pre_validate_and_infer_types()
 {
+    if (is_dynamic())
+    {
+        return;
+    }
+
     const auto& x_pshape = get_input_partial_shape(0);
     const auto& w_pshape = get_input_partial_shape(1);
     const auto& r_pshape = get_input_partial_shape(2);

src/ngraph/op/fused/partial_slice.cpp

@@ -228,4 +228,5 @@ void op::PartialSliceBackprop::pre_validate_and_infer_types()
                           "Argument element type must be f16, bf16, f32, f64 or dynamic (got ",
                           input_element_type,
                           ").");
+    set_output_type(0, get_input_element_type(0), PartialShape::dynamic());
 }

src/ngraph/op/fused/rnn_cell.cpp

@@ -77,6 +77,11 @@ op::RNNCell::RNNCell(const Output<Node>& X,
 
 void op::RNNCell::pre_validate_and_infer_types()
 {
+    if (is_dynamic())
+    {
+        return;
+    }
+
     const auto& x_pshape = get_input_partial_shape(0);
     const auto& w_pshape = get_input_partial_shape(1);
     const auto& r_pshape = get_input_partial_shape(2);

src/ngraph/op/fused/split.cpp

@@ -29,11 +29,6 @@ op::Split::Split(const Output<Node>& data, const int axis, const size_t num_spli
     , m_axis{axis}
     , m_num_split{num_split}
 {
-    // Create dynamic-typed outputs. Actual shape/type will be computed during shape inference
-    for (size_t i = 0; i < num_split; i++)
-    {
-        set_output_type(i, element::dynamic, PartialShape::dynamic());
-    }
     constructor_validate_and_infer_types();
 }
 
@@ -41,18 +36,25 @@ op::Split::Split(const Output<Node>& data, const int axis, const std::vector<siz
     : FusedOp({data})
     , m_split_evenly{false}
     , m_axis{axis}
+    , m_num_split{0}
     , m_splits{splits}
 {
-    // Create dynamic-typed outputs. Actual shape/type will be computed during shape inference
-    for (size_t i = 0; i < splits.size(); i++)
-    {
-        set_output_type(i, element::dynamic, PartialShape::dynamic());
-    }
     constructor_validate_and_infer_types();
 }
 
 void op::Split::pre_validate_and_infer_types()
 {
+    // Create dynamic-typed outputs. Actual shape/type will be computed during shape inference
+    for (size_t i = 0; i < std::max(m_splits.size(), m_num_split); i++)
+    {
+        set_output_type(i, input(0).get_element_type(), PartialShape::dynamic());
+    }
+
+    if (is_dynamic())
+    {
+        return;
+    }
+
     const auto shape = input(0).get_shape();
 
     m_axis = adjust_axis_value(m_axis, shape.size());

src/ngraph/op/util/fused_op.cpp

@@ -42,24 +42,12 @@ op::util::FusedOp::FusedOp(const std::string& node_type, const NodeVector& args)
 
 void op::util::FusedOp::validate_and_infer_types()
 {
-    // Bail out if any of the shapes are unknown since fused op decomposition
-    // typically requires fully-determined static types.
-    //
-    // In the absence of decomposition, we will not know how many outputs this
-    // fused op has, so we conservatively create and set a single output to
-    // facilitate downstream ops that would like to use this op as an argument.
-    // Multi-output fused ops (e.g., split) should create these outputs in their
-    // constructors instead.
-    for (size_t i = 0; i < get_input_size(); i++)
-    {
-        if (!get_input_partial_shape(i).is_static())
+    pre_validate_and_infer_types();
+
+    if (!can_decompose_with_partial_shapes() && is_dynamic())
     {
-            set_output_type(0, element::dynamic, PartialShape::dynamic());
         return;
     }
-    }
-
-    pre_validate_and_infer_types();
 
     auto subgraph_outputs = decompose_op();
     auto subgraph = extract_subgraph(subgraph_outputs, get_arguments());

src/ngraph/op/util/fused_op.hpp

@@ -31,10 +31,23 @@ namespace ngraph
             {
             public:
                 bool supports_decompose() const override { return true; }
+                // Fused op decomposition can be performed in the presence of
+                // partial shapes
+                virtual bool can_decompose_with_partial_shapes() { return false; }
+                // Shape inference that will use fused op decomposition to infer
+                // shapes and types of output elements. Ops can choose to override
+                // and provide a more direct implementation.
                 void validate_and_infer_types() override;
 
-                /// Pre and post validation hooks for op-specific actions
+                // Pre-validation hook that will be invoked before op
+                // decomposition in validate_and_infer_types().
+                // Can be used for attribute validation and setting types/shapes
+                // that can be inferred without requiring op decomposition.
+                // Can also be used to set shape specialization hints
+                // (set_input_is_relevant_to_shape())
                 virtual void pre_validate_and_infer_types() {}
+                // Post-validation hook that will be invoked after op decomposition
+                // in validate_and_infer_types().
                 virtual void post_validate_and_infer_types() {}
                 void generate_adjoints(autodiff::Adjoints& adjoints,
                                        const NodeVector& deltas) override;