llvm / llvm/circt

[firtool] Run RemoveUnusedPass after eliminating named wires

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Description

circuit Foo :
  module Foo :
    input a : UInt<1>
    node y = a

Output with PR #3149.

module Foo(
  input a);

Even with https://github.com/llvm/circt/pull/3149, we cannot remove port a since port a is used by node y at FIRRTL level.
Once we implement https://github.com/llvm/circt/issues/3146, turn on HW::RemoveUnusedPass after eliminating named wires.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with firtool's handling of named wires and the implementation of issue #3146, using PR #3149 as context. Once named wires are eliminated, enable HW::RemoveUnusedPass; the example is complete when the unused port a is removed from the generated Verilog.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
compilers
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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