Add a dont-care operation to avoid dangling input nodes?

In some cases we may define operations with multiple input ports, where not all input ports are used all the time. It would be good to do something similar to a sink operation in #132 (closed) to connect "something" to those ports.

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marked this issue as related to #132 (closed)

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assigned to @frask53

Is this feature actually nessecary? I suggest just using the Constant operation set to zero instead.

This "dont-care" operation would still just work in the same way, unless it's supposed to supply some sort of undefined value to the sfg? In which case that undefined value would propagate further in the sfg making most other outputs undefined as well.

In what way is it supposed to work? If it works just like a constant, I suggest closing this issue.

Good question! That should probably work as far as I can tell. One potential problem is that a constant zero should actually be connected to the input (so should be realized as a memory and possibly partitioned to a memory and with connections to that memory), while this corresponds to something else. But not really sure exactly what at this stage...

I'll add a new label for this and suggest that you prioritize another issue. :-)

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unassigned @frask53

And, yes, from a constant propagation perspective it should work just as a zero input. Just thinking of more complex PEs/operations where, say, there is a mode selector which sometimes doesn't use one of the inputs.

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When implementing the MADS operation (multiply-add/sub) I added a flag to override the value of one input port. So the input to MADS that use this flag is dont care.

As such, I think that this issue is relevant again.

assigned to @simbj106

mentioned in merge request !469 (merged)

closed with merge request !469 (merged)