Subject: Re: Connect-ResolveTo stmts
From: Kevin Cameron (Kevin.Cameron@nsc.com)
Date: Fri Mar 08 2002 - 21:34:54 PST
[ I don't think I'll be attending the meeting on Monday (if there is one) since
I'll be attending HDL-Con - I presume others will be going too.]
Srikanth Chandrasekaran wrote:
> Hi all,
>
> Problem:
> With the current version of the LRM there is lot of ambiguity with regards to
> which of the rules apply when trying to do discipline resolution
>
> connect x y b resolveTo b
> connect x y resolveTo x
> connect x y a resolveTo a
>
> In the above set of rules it is not clear, when two nets having disciplines x
> & y will be resolved to b, z, or a.
>
> Also it is not clear in the LRM whether the resolved discipline should be part
> of the list specified.
Shouldn't be a requirement.
> Solution: Best Match Fits
> When there is an exact match for the set of disciplines specified, the
> resolved discipline would be as per the rule specified in the exact match. In
> the above case x,y would resolve to discipline x. It shall be an error to
> specify more than one rule with the exact fit. The resolved discipline need
> not be one of the disciplines specified in the discipline list.
>
> When there is no exact fit, then the resolved discipline would be based on the
> subset of the rules specified. If there is more than one subset matching a set
> of disciplines, the simulator shall give an error message on ambigous connect-resolveto
> specification saying that there is more than one rule that matches for resolving the
> disciplines.
>
> Example 1:
> ----------
> connect x y a resolveTo a
> connect x y resolveTo x
>
> x,y would resolve to x.
> x,y,a would resolve to a
> y,a would resolve to a
>
> Example 2:
> ----------
> connect x y a resolveto a
> connect x y resolveTo x
> connect x y b resolveto z
>
> x,y would resolve to x
> x,y,b would resolve to z
> y,a would resolve to a
>
> Example 3:
> ----------
> connect x y a resolveto a
> connect x y b resolveto b
>
> x,y would resolve to "ERROR: Ambigous"
> y,a would resolve to a
> y,b would resolve to b
>
> Example 4:
> ----------
> connect x y resolve to x
> connect x y resolve to y // ERROR: Conflict
>
> cheers,
> Sri
I'd agree that missing rules should be an error, but over-specifying the rules
should (in my opinion) just generate a warning. It could be difficult to fix the
rules in practice when re-using IP. For now I would just take the "first seen"
rule or leave it as vendor specific.
There is no implication that either rule is "wrong" when two apply.
Kev.
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