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No support for parameterized interface in module "signal" list. #1104

veripoolbot opened this issue Nov 9, 2016 · 1 comment

No support for parameterized interface in module "signal" list. #1104

veripoolbot opened this issue Nov 9, 2016 · 1 comment


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@veripoolbot veripoolbot commented Nov 9, 2016

Author Name: Adrian Wise
Original Redmine Issue: 1104 from

In SystemVerilog there is, I believe - I admit to being very new to SystemVerilog - no syntax to be able to pass parameters to an interface type when it is used in the signal list of a module.

Instead in the signal list the keyword 'interface' should be used.

See the example code, attached, which essentially lifted directly from Section 25.8 "Parameterized interfaces" of IEEE 1800-1012. (I've deleted the tasks which are not relevant to this issue, and changed a 'ref' on 'data' to 'input'/'output' in the modports so this should be supported by Verilator.)

When compiled this gives:

$ verilator -lint-only parameterized_interfaces.v
%Error: parameterized_interfaces.v:23: Unsupported: virtual interfaces
%Error: parameterized_interfaces.v:29: Unsupported: virtual interfaces
%Error: Exiting due to 2 error(s)
$ verilator -V
Verilator 3.888 2016-10-14 rev verilator_3_888

I don't think that this is an example of a virtual interface, so at the very least this is a confusing error message.

It's tempting to change, in this example, the keyword 'interface' for the type 'simple_bus', for example:

module memMod(simple_bus a);

(or use the modports simple_bus.slave / simple_bus.master as appropriate)

But this is incorrect because that's a reference to a simple_bus with default parameters - not one with the parameters for the bus that's actually connected to the CPU or memory.


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@veripoolbot veripoolbot commented Dec 22, 2016

Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2016-12-22T02:00:45Z

Message fixed.

This unfortunately cannot be supported soon, as Verilator needs to resolve all types during a first pass (before parameters are known) and this cannot be done with generic interfaces. A major restructuring would have to happen first.

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