Don, My concerns have gotten stronger with further thought. Now I am concerned with even non-hierarchical names in the overrides, as you can get circularities even with local references. In the HDL, you cannot get a circularity with a local reference, because a parameter value expression cannot make a forward reference to a parameter declared later (except via an illegal hierarchical name). But your proposal would allow a parameter value to be defined in terms of one declared later in the same module (which could have a value defined in terms of the first). This is an inherent problem of bringing these overrides in from outside the normal source language order. I have also gotten more concerned with the hierarchical names. There do already exist situations that allow circularities (such as upward defparams). These should never have been allowed in the first place, and the situation should not be worsened by allowing more such situations. This new situation would be even worse, since it would add a whole new layer of overriding on top of the existing ones, greatly increasing the complexity of interactions. By far the worst form of these circularities occur when they interact with generates. These could result in generating different hierarchies for the same design, all equally valid, depending on exactly how the resolution is done. Extra restrictions were placed on upward flow of parameter values across generates to prevent this. I don't see that protection in this config proposal. The only quick fix I can see for this is to disallow any reference to design parameters in the values provided by the config. I assume that the enhancement would be of very little use with this restriction. More design work is needed to come up with a version of this enhancement that gives the desired functionality while avoiding these problems. Steven Sharp sharp@cadence.com -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.Received on Mon Dec 17 08:42:37 2007
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