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Extend UNUSED to flag signals which are not in the cone of a module output #1395

veripoolbot opened this issue Feb 1, 2019 · 2 comments


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@veripoolbot veripoolbot commented Feb 1, 2019

Author Name: Geoff Barrett
Original Redmine Issue: 1395 from

The following code produces no warnings:

module unused_vars (
  input var logic ck,
  output var logic c

logic d, q;

always_ff @(posedge ck) q <= d;
always_comb d = q;

always_comb c = '0;

endmodule : unused_vars

The combination of UNUSED and UNOPTFLAT means (I think) that we will always get a warning if signals are not either in the cone of an output or a nonblocking assignment. However, d and q are only used by each other and can be eliminated from the module and it would be very useful to get a warning about this.

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@veripoolbot veripoolbot commented Feb 7, 2019

Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2019-02-07T01:00:38Z

Agreed this is useful and the base info is in the structures, but can't get to it soon.

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