From: Steven Sharp (sharp@cadence.com)
Date: Tue Jul 02 2002 - 12:28:37 PDT
Precedence: bulk
>Are there any VPI experts here?? I have the following
>potential VPI related item for the errata list.
I'm not a VPI expert, but I have discussed it with one
(and I stayed at a Holiday Inn last night).
>Indexed part-selects (+: and -:) do not seem to have
>a representation in VPI.
>
>Can anyone else confirm this, or point out for me how
>they are represented?
>
>Is the vpiConstantSelect property of vpiPartSelect objects
>relevant? That is,
>
> vpiConstantSelect == false ==> indexed part-select
> vpiConstantSelect == true ==> regular part-select
Apparently this is the case.
>But, how does one distinguish +: from -:?
Well, it shouldn't have mattered the way I thought it was supposed to work,
but somebody added extra flexibility that causes problems. I thought
that the base expression was always supposed to be the left index, since
it appears at the left position. Then the direction would be determined
by the direction of the declaration, and the choice of +: or -: would have
to be consistent with that. However, it looks like the spec allows the
base to be either the left or right index, based on the direction of the
select versus the direction of the declaration. So now you can't tell what
is going on from VPI unless you can determine the direction of the select.
Sigh.
So we need to either eliminate this extra flexibility (which isn't really
needed), or add another attribute to part selects in VPI.
Steven Sharp
sharp@cadence.com
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