Re: [Iverilog-devel] Numeric attributes

[Martin W. <ic...@ma...>]

Given that nobody has asked for anything more, it's fair to assume that the 
existing support for attributes in the target API is adequate. Providing we 
correctly parse and discard other attributes, it doesn't matter what use 
other tools make of them.

Stephen Williams wrote:
> Attributes that I run into in i.e. the Xilinx context tend to be
> either simple booleans, or strings. For example, INIT values tend to
> be strings, not large numeric values. Parameters seem to be how people
> pass around complex numeric values, which makes sense.
> 
> I might put some effort into attributes, but currently they are not at
> all available at run time, and they probably don't make much sense
> there.
> 
> On Tue, Nov 19, 2019 at 10:18 AM Martin Whitaker
> <ic...@ma...> wrote:
>>
>> Indeed, the standard allows an attribute value to be any constant
>> expression. So real values would be allowed too. But nobody has complained
>> that they aren't accepted, so I guess they aren't widely used.
>>
>> Stephen Williams wrote:
>>> Recently I noticed that there may be a problem with numeric attributes
>>> at the ivl_target.h API. Specifically, the API is converting numeric
>>> attributes to host integers. This winds up truncating values to 64
>>> (63) bits, and drops x and z bit values. My reading of the standard is
>>> that numeric attributes have no such limitations, so it appears that
>>> the API is wrong.
>>>
>>> So, my questions are:
>>>
>>> 1) Anybody out there using attributes? They are accessible at the
>>> ivl_target.h API level, so if you are writing code generators, you
>>> might be using attributes. I don't think they are available through
>>> PLI.
>>>
>>> 2) Anybody have an opinion on whether numeric attributes are treated
>>> as 4-value logic in other tools? Or am I fooling myself and numeric
>>> attributes really do evaluate down to host integers?
>>>
>>> 3) What do other tools do?
>>>
>>>
>>
>>
>>
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> 
>