<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/93294>93294</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Fine-tune code coverage reports documentation is lacking
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          JVApen
      </td>
    </tr>
</table>

<pre>
    We have been experimenting with [SourceBasedCodeCoverage](https://clang.llvm.org/docs/SourceBasedCodeCoverage.html#impact-of-llvm-optimizations-on-coverage-reports) and noticed that there is a huge overhead in writing the .profraw files. (time after the tests ran and shut down)

We found [2023 LLVM Dev Mtg - Using Clang's source-based code coverage at scale](https://youtu.be/RlySdMe3Eg0?si=lNCJb4F_veWD8pNk&t=621) (timepoint when opening the video). That presentation seems to suggest that `-fprofile-list=<file>` can be used to limit the scope that is being reported. After searching, we found the following section regarding profile guided optimization that explains the option: https://clang.llvm.org/docs/UsersManual.html#instrumenting-only-selected-files-or-functions

Without seeing that video, we would never have figured out that this was an option. I feel it is worth documention this explicitly.
</pre>
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