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steveicarus / iverilog

Icarus Verilog
https://steveicarus.github.io/iverilog/
GNU General Public License v2.0
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VPI: load tracing with vpiDriver and vpiLoad #197

Open yanghao opened 6 years ago

yanghao commented 6 years ago

It seems iverilog does not yet support load tracing in its vpi implementation (no vpiDriver/vpiLocalDriver/vpiLoad/vpiLocalLoad defined).

Are there an alternative way to do this in iverilog or is this feature planned to be supported in the future?

Best Regards, Yanghao

martinwhitaker commented 6 years ago

Apart from the $countdrivers system function (which is implemented), I don't know of any other way to get such information.

When I have some free time, I'll look at how hard it would be to add these functions.

yanghao commented 6 years ago

Thanks @martinwhitaker

The use case I have is to automatically detect reg/wire being driven already through VPI, because in this case assigning new values to an already-driven nets through vpi_put_value() will not have any effect. So better already warns user loudly at this stage.

I implemented the load tracing code through VPI initially for icarus only to find it is not supported, and tried same thing on vcs it works properly.

I did not find this $countdrivers() C counterpart from any of the iverilog header files, so I guess it is only available from within verilog code, which I cannot use due to all of my stuff is supposed to go through VPI only.