Re: [Iverilog-devel] Always blocks with out delays (pr1862744)

[Stephen W. <st...@ic...>]

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Cary R. wrote:
| --- On Fri, 4/18/08, Stephen Williams <st...@ic...> wrote:
|
|> Or have it return an enum with a range:
|>
|> ~   NO_DELAYS  = 0
|> ~   NO_KNOWN_DELAYS = 1
|> ~   KNOWN_DELAYS = 3
|
| If this is the route I go I think it should be NO_DELAY,
POSSIBLE_DELAY and DEFINITE_DELAY. I think the code will be cleaner if
we pass a control flag vs checking both possibilities and combining them
correctly. Can you think of a case where we would need to know the three
different states?

Your names are much better, yes.

Well, if you pass a control flag to the calculation of this state,
then you are implying that it is calculated on demand, possibly
multiple times (and possibly no times) whereas if you just calculate
the more expressive value, then you can reuse the value for different
needs. (Again, perhaps you need it zero times.)

My sense is that if every always statement is going to need this
value, then it is going to be needed almost always, and might as
well be calculated during elaboration. It strikes me that it will
be very easy to calculate during elaboration, skipping the need
for a post-process recursive test later when the data is needed.

It can be that the expressive enum value be hidden behind a pair
of boolean methods that the clients use, so this method if calculating
the expressive value can have any reasonable interface.

Hmm, I'm thinking about where this information may be used, and
I'm starting to realize that only NO_DELAY is useful. If you have
an always statement, you want to generate a warning if it IS
NO_DELAY, and if the NetProc is a function definition you want
to generate an error if it is NOT NO_DELAY.

- --
Steve Williams                "The woods are lovely, dark and deep.
steve at icarus.com           But I have promises to keep,
http://www.icarus.com         and lines to code before I sleep,
http://www.picturel.com       And lines to code before I sleep."
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