#954 specify block delays break when multiple inputs have the same driver

[Cary R.]

The attached code demonstrates a problem in modpath generation. This results in incorrect delays without a warning and SDF back annotation problems (not shown). I believe the problem only happens if the same signal (nexus) drives more than one input to a model that also has a specify block. Yes, specify blocks are not fully supported, but this part was previously thought to be working correctly so I am raising the priority accordingly, failure without a warning and no workaround.

The fundamental issue is that even though the same nexus drives the inputs the individual paths still need to be kept intact so the correct delay can be used. Currently they are combined into a single path. It is also interesting to note that the runtime does not complain when given two matching modpaths. I would have expected this to be an error. The problem appears to be in the compiler/code-generator.

I do not currently have time to work on this. I have a much larger example that may have more subtlety than the attached example so I will have to run that once this is fixed to see if there are other issues.