[torchlib] Allow calling shared functions from other onnx functions

[justinchuby]

Currently the torchscript evaluator does not support calling OnnxFunctions from within an OnnxFunction. We should enable this to allow shared implementations. To do this, we will need to keep references of the called functions inside an OnnxFunction.

[BowenBao]

Done by #725 ?

[justinchuby]

Ahh that’s right! I remember this pr but got a test error when I did this. I must have confused myself. Thanks!

[justinchuby]

So we need to use add_module_call it seems? Looks like the graph builder is not handling cases where a function calls another (when using OnnxFunction to_function_proto).

I can think of two options:

1. Create a new API in OnnxFunction to return a list of function protos used by the function (recursively) (deduplication would be an issue)
2. Record the functions in the Graph on the fly Record OnnxFunctions in called functions #629
3. Do what to_model_proto does (I haven't looked)

[BowenBao]

@justinchuby We don't need add_module_call for this, the rest makes sense. There is existing api IRFunction.to_graph_and_functions / IRFunction.called_functions used by OnnxFunction.to_model_proto to grab inner functions. I believe all we need is exposing the api at OnnxFunction level and use it in TorchScriptGraph.add_function_call.