[IR] Introduce node convenience functions

docs/ir/ir_api/ir_convenience.md

@@ -12,4 +12,6 @@
 .. autofunction:: replace_all_uses_with
 .. autofunction:: replace_nodes_and_values
 .. autofunction:: create_value_mapping
+.. autofunction:: insert_nodes_in_value
+.. autofunction:: remove_nodes
 ```

onnxscript/ir/_convenience/__init__.py

@@ -14,6 +14,8 @@
     "replace_all_uses_with",
     "create_value_mapping",
     "replace_nodes_and_values",
+    "insert_nodes_in_value",
+    "remove_nodes",
 ]
 
 from typing import Mapping, Sequence, Union
@@ -335,6 +337,18 @@
     return values
 
 
+def _update_graph_or_function_outputs(
+    graph_or_function: _core.Graph | _core.Function,
+    old_values: Sequence[_core.Value],
+    new_values: Sequence[_core.Value],
+):
+    """Update graph/function outputs"""
+    replacement_mapping = dict(zip(old_values, new_values))
+    for idx, graph_or_function_output in enumerate(graph_or_function.outputs):
+        if graph_or_function_output in replacement_mapping:
+            graph_or_function.outputs[idx] = replacement_mapping[graph_or_function_output]
+
+
 def replace_nodes_and_values(
     graph_or_function: _core.Graph | _core.Function,
     /,
@@ -367,11 +381,171 @@
     # Reconnect the users of the deleted values to use the new values
     replace_all_uses_with(old_values, new_values)
     # Update graph/function outputs if the node generates output
-    replacement_mapping = dict(zip(old_values, new_values))
-    for idx, graph_or_function_output in enumerate(graph_or_function.outputs):
-        if graph_or_function_output in replacement_mapping:
-            graph_or_function.outputs[idx] = replacement_mapping[graph_or_function_output]
+    _update_graph_or_function_outputs(graph_or_function, old_values, new_values)
 
     # insert new nodes after the index node
     graph_or_function.insert_after(insertion_point, new_nodes)
     graph_or_function.remove(old_nodes, safe=True)
+
+
+def _find_inputs_outputs(
+    nodes: Sequence[_core.Node],
+) -> tuple[Sequence[_core.Value], Sequence[_core.Value]]:
+    """Find the values that are considered as inputs and outputs in a sequence of nodes"""
+    # Search the unique inputs/outputs in new_nodes, keeping the order.
+    all_inputs = dict.fromkeys(sum([node.inputs for node in nodes], ()))
+    all_outputs = dict.fromkeys(sum([node.outputs for node in nodes], ()))
+    # A value is considered as input if it is not any output.
+    inputs = tuple(val for val in all_inputs if val not in all_outputs)
+    # A value is considered as output if it is not any input.
+    outputs = tuple(val for val in all_outputs if val not in all_inputs)
+    return inputs, outputs
+
+
+def insert_nodes_in_value(
+    values: _core.Value | Sequence[_core.Value], new_nodes: Sequence[_core.Node]
+) -> None:
+    """Inserts a sequence of nodes into the provided value(s).
+
+    This allows to insert a list of LINKED nodes (over the same context) at
+    a specific point in the graph.
+
+    For example, suppose we have the following graph::
+
+        input -> A := node_A(input) -> B := node_B(A) -> C := node_C(B) -> output
+
+    We want to insert [node_M, node_N] at B value::
+
+        >>> from onnxscript import ir
+        >>> input = ir.Input("input")
+        >>> node_A = ir.node("op_A", [input])
+        >>> B = ir.Value(name="B")
+        >>> node_B = ir.node("op_B", node_A.outputs, outputs=[B])
+        >>> node_C = ir.node("op_C", node_B.outputs)
+        >>> # Create a new sequence to insert
+        >>> input_2 = ir.Input("input_2")
+        >>> node_M = ir.node("op_M", [input_2])
+        >>> node_N = ir.node("op_N", node_M.outputs)
+        >>> # Insert nodes in B
+        >>> insert_nodes_before_value(node_B.outputs, [node_M, node_N])
+        >>> len(node_B.outputs)
+        1
+        >>> node_B.outputs[0].consumers()[0].op_type
+        'op_M'
+        >>> len(node_C.inputs)
+        1
+        >>> node_C.inputs[0].producer().op_type
+        'op_N'
+        >>> node_C.inputs[0].name
+        'B'
+
+    When values is a sequence, the set of nodes must have the same number
+    of inputs and outputs, then they are zipped into pairs: first value is
+    replaced with the first input/output, and so on.
+
+    Args:
+        values: The value(s) where to insert the nodes.
+        new_nodes: The nodes to insert in the graph.
+    """
+    if not isinstance(values, Sequence):
+        values = (values,)
+
+    # Search the unique inputs/outputs in new_nodes, keeping the order.
+    inputs, outputs = _find_inputs_outputs(new_nodes)
+
+    # Sanity check.
+    if len(values) != len(inputs):
+        raise ValueError(f"The number of values and inputs ({inputs}) in new_nodes must match.")
+    if len(values) != len(outputs):
+        raise ValueError(f"The number of values and outputs ({outputs}) in new_nodes must match.")
+
+    # Propagate relevant info.
+    for val, in_val, out_val in zip(values, inputs, outputs):
+        # Propagate relevant info from value to out_value.
+        # TODO(Rama): Perhaps this should be a separate utility function.
+        out_val.type = val.type
+        out_val.shape = val.shape
+        out_val.name = val.name
+        # Propagate relevant info from value to in_value.
+        # TODO(Rama): Perhaps this should be a separate utility function.
+        in_val.type = val.type
+        in_val.shape = val.shape
+        # Rename each value, following each input.
+        val.name = in_val.name
+
+    # Insert the new nodes in two steps:
+    # 1. Reconnect the users of values to the outputs
+    replace_all_uses_with(values, outputs)
+    # 2. Reconnect the users of inputs to values
+    replace_all_uses_with(inputs, values)
+
+    # Update graph if there is one:
+    if (graph := values[-1].graph) is not None:
+        # Update graph/function outputs if the node generates output
+        _update_graph_or_function_outputs(graph, values, outputs)
+
+        # Insert new nodes if there is a graph
+        graph.extend(new_nodes)
+        graph.sort()
+
+
+def remove_nodes(nodes: Sequence[_core.Node]) -> None:
+    """Remove a sequence of nodes.
+
+    This allows to delete a list of LINKED nodes (over the same context).
+
+    For example, suppose we have the following graph::
+
+        input -> A := node_A(input) -> B := node_B(A) -> C := node_C(B) -> output
+
+    We want to prune [node_B]::
+
+        >>> from onnxscript import ir
+        >>> input = ir.Input("input")
+        >>> node_A = ir.node("op_A", [input])
+        >>> node_B = ir.node("op_B", node_A.outputs)
+        >>> node_C = ir.node("op_C", node_B.outputs)
+        >>> # Delete node_B
+        >>> remove_nodes([node_B])
+        >>> len(node_A.outputs[0].consumers())
+        1
+        >>> node_A.outputs[0].consumers()[0].op_type
+        'op_C'
+        >>> len(node_C.inputs)
+        1
+        >>> node_C.inputs[0].producer().op_type
+        'op_A'
+        >>> node_B.inputs
+        (None,)
+        >>> len(node_B.outputs)
+        1
+        >>> len(node_B.outputs[0].consumers())
+        0
+
+    Args:
+        nodes: The nodes to remove.
+    """
+    # Search the unique inputs/outputs in new_nodes, keeping the order.
+    inputs, outputs = _find_inputs_outputs(nodes)
+
+    # Sanity check.
+    if len(inputs) != len(outputs):
+        raise ValueError(
+            f"The number of inputs ({inputs}) and outputs ({outputs}) in nodes must match."
+        )
+
+    # Remove nodes, in several steps:
+    # 1. Reconnect the users of outputs with inputs
+    replace_all_uses_with(outputs, inputs)
+    # 2. Detach nodes for their inputs
+    for node in nodes:
+        for i in range(len(node.inputs)):
+            node.replace_input_with(i, None)
+
+    # Update graph if there is one:
+    if (graph := inputs[-1].graph) is not None:
+        # Update graph/function outputs if the node generates output
+        _update_graph_or_function_outputs(graph, outputs, inputs)
+
+        # Drop nodes from graph
+        graph.remove(nodes, safe=True)