RE: [sv-ac] P1800 SV-AC: vote on #1549

I know the discussion on this topic has evolved far beyond the
keep-it-simple phase, but just for a matter of perspective...

I brought up this issue in an SVA training class I presented last week.  I
asked the students what they preferred, using the nearly same scenarios in
Dimitry's message, below.  Every student preferred requiring all untyped
arguments be listed first, and once an argument is typed, any arguments
without a specific type that follow inherit the type of the preceding
argument.  All the students felt this was the most intuitive behavior.  Some
were very surprised that any other behavior would even be considered.   None
of the students felt it was necessary to switch back to untyped args once a
type had been specified, regardless of whether an existing keyword were
used, or a new keyword was invented.

Granted, my query to the class was far from a scientific survey.  Only two
user companies were represented, and though both companies already have
legacy SVA code, the students did not know what, if any, assumptions
regarding untyped/typed arguments had been made in their existing SVA
properties and sequences.

No matter what is done, there will be a backward compatibility issue.  Since
it is an issue no matter what, I am in favor of doing what is simple and
intuitive to users.  Any untyped args must be listed first in the argument
list.  Once an arg type is specified, subsequent args without a type inherit
the type of the previous arg.  If some tool was already interpreting the
standard this way, then users of that tool will not have a backward
compatibility problem.  If some tool was already interpreting the standard
differently, that tool can provide a backward compatibility switch.  

Stu
~~~~~~~~~~~~~~~~~~~~~~~~~
Stuart Sutherland
stuart@sutherland-hdl.com
+1-503-692-0898
  

> -----Original Message-----
> From: owner-sv-ac@server.eda.org 
> [mailto:owner-sv-ac@server.eda.org] On Behalf Of Korchemny, Dmitry
> Sent: Wednesday, October 04, 2006 11:42 PM
> To: john.havlicek@freescale.com; Eduard.Cerny@synopsys.com
> Cc: piper@cadence.com; Bassam.Tabbara@synopsys.com; 
> sv-ac@server.eda.org
> Subject: RE: [sv-ac] P1800 SV-AC: vote on #1549
> 
> One more issue is the backward compatibility. We had initially a
> discussion about interpreting parameter types in properties/sequences.
> E.g.,
> 
> sequence s(bit a, b);
> ...
> endsequence
> 
> One interpretation was that a is typed while b is untyped. 
> The other one
> (which won) was that both a and b are of type bit. But there 
> were people
> who wrote their property library according the first 
> interpretation. It
> is acceptable to request from them to change the implementation:
> 
> sequence s(bit a, implicit b);
> 
> but to change the usage
> 
> sequence s(b, bit a);
> 
> in unacceptable.
> 
> Thanks,
> Dmitry
> 
> -----Original Message-----
> From: owner-sv-ac@server.eda.org 
> [mailto:owner-sv-ac@server.eda.org] On
> Behalf Of John Havlicek
> Sent: Monday, September 11, 2006 7:40 PM
> To: Eduard.Cerny@synopsys.com
> Cc: piper@cadence.com; Bassam.Tabbara@synopsys.com; 
> sv-ac@server.eda.org
> Subject: Re: [sv-ac] P1800 SV-AC: vote on #1549
> 
> Hi Ed:
> 
> I think Dmitry and, perhaps, others did not like requiring the
> implicitly typed arguments to be placed first in the argument list.
> 
> It is fair enough to ask the other committees to have a look at
> "implicit" to see what it can do for them.
> 
> I am a little worried that if we remove "implicit" then we may be
> discarding our first choice solution on the rumor of pushback from the
> champions.
> 
> J.H.
> 
> 
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> > Thread-Index: AcbTb8rEWEqxRyu2Qp2lo5jzRQiFrgCQZHCQAAD3XpA=
> > From: "Eduard Cerny" <Eduard.Cerny@synopsys.com>
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> > 
> > I think that the issue is that we introduce a new keyword "implicit"
> and
> > there is generally resistance to introducing new keywords 
> that have a
> > very narrow usage, in this case only in the list of arguments to
> > properties and sequences. Therefore, either the other 
> committees find
> it
> > useful in other contexts or we perhaps may have to retract it. In
> fact,
> > it is not obvious to me that we do really need it, because we could
> > require that all untyped arguments be placed first on the list.
> > =20
> > Best regards
> > ed
> > =20
> > 
> > 
> 
>