Re: [myhdl-list] Small buglet

[Thomas H. <th...@ct...>]

Jan Decaluwe schrieb:
> Thomas Heller wrote:
>> While working with Python generators in a testbench to supply test data to my instances,
>> I found that the myhdl.instances() function not only returns MyHDL instances but also
>> these generators.
> 
> Right. Sometimes I think that myhdl.instances() is a result
> of me trying to be too clever, and therefore not really a good
> idea. Suppose it would be required to always return instances
> explicitly, would anyone have missed it?

Well, I like instances() a lot.  It allows me to split one 'instance'
into two or more which is sometimes a little more elegant, and avoids the error that
I forget to include the new instance into the return statement.
(toVerilog usually complains about some signals not been driven in that case,
but the simulation does not, IIRC.)

When I was first playing with myhdl, I missed 'instances' so much (since it wasn't mentioned
in the first chapters of the manual) that I decided to implement it myself.  Luckily
I found it before the implementation did really work.

> Anyway. I think that you expect that the function only finds
> instances created by the MyHDL decorators @instance, @always
> and @always_comb (and also the "hierarchical" instances of
> course.) Those decorators could return special objects that
> can be easily be looked up by type. That's indeed what currently
> happens with @always and @always_comb - but not with
> @instance, which creates a generator directly.
> 
> Before 0.5, MyHDL had no decorators and the only option was
> to use generators directly. Therefore, it was not possible
> to differentiate between "MyHDL" generators and other ones.
> At this point, myhdl.instances() is still compatible with
> that behavior.
> 
> In the future, I believe the function should be modified
> so that it works like you expect. It's a good idea to
> require using MyHDL decorators for instances. The code
> becomes clearer, and as you say, plain generators have
> other uses, also in MyHDL code.
> 
> In the mean time, returning instances explicitly is a good
> workaround. Perhaps better than the "feature" :-)
> 
> Feedback welcome.

Thanks,
Thomas