llvm / llvm/circt

[FIRRTL] Improve Error Message on Uninferred Reset of Uninstantiated Module

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enhancement good first issue
Dominant language
C++
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Description

Currently, the following FIRRTL Circuit will fail in `InferResets` because of an uninstantiated module. This error is somewhat confusing and it would be better to also indicate that this module is uninstantiated:

```
circuit Foo :
module Bar :
input clock : Clock
input reset : Reset

skip

module Foo :

skip
```

This currently produces:

```
# firtool Tmp.fir
Tmp.fir:2:10: error: 'firrtl.module' op has an abstract reset type port "reset" after InferResets
module Bar :
^
```

h/t @cedric-orban

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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 the InferResets pass and the firtool diagnostic shown in the issue, using the provided FIRRTL circuit as a reproducer. Update the error so it also identifies that the module is uninstantiated, then rerun firtool on the example and verify the diagnostic is clearer.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
compilers
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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