Node setDatatype is too strict

Context

Current setDatatype is too strict and override output datatype where it should not.

An example is the Shape Operator that should always return a INT64 Tensor by design.

I propose to introduce a new method forwardDataType that for a given node set the datatype of the output using the datatype of its input.

A current use case is the shuffle layer: https://gitlab.eclipse.org/-/project/5139/uploads/6ad9fc3fc64740b31b696a3f20308553/shuffle_layer.onnx

Ideally all the dim computation should be done using INT64

Implementation idea

This would be done by adding forwardDataType in OperatorTensor. By default, this function check that every input has the same datatype and set this datatype to the outputs.

This would be override by specific operator such as:

• Reshape: Input 1 need to be INT64, output is the same as input 0
• Shape: Whatever the input, the output is always INT64.

In order to maintain current API, GraphView::setDatatype would call GraphView::forwardDataType with a deprecation warning.

GraphView::forwardDataType would have two signatures:

• bool GraphView::forwardDataType(dtype): Return true if successfull. the same dtype is forwarded to all inputs.
• bool GraphView::forwardDataType(std::vector<dtype>): Return true if successfull. Specify different dtype for each graph inputs.