<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/144211>144211</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Flang][CI] Merge CI rejects any change to llvm/Support/Compiler.h
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            flang
      </td>
    </tr>

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

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

<pre>
    I noticed a build failure after making a change to `llvm/include/llvm/Support/Compiler.h` .
https://github.com/llvm/llvm-project/pull/143222#issuecomment-2971658629

The build log shows the following error:

> fatal error: file 'C:\Users\tcwg\llvm-worker\flang-arm64-windows-msvc\llvm-project\llvm\include\llvm\Support\Compiler.h' has been modified since the precompiled header 'C:/Users/tcwg/llvm-worker/flang-arm64-windows-msvc/build/tools/flang/lib/Parser/CMakeFiles/FortranParser.dir/./cmake_pch.cxx.pch' was built: size changed (was 27102, now 27125)

It appears that the build system does not properly detect and rebuild the precompiled header when one of its dependencies is updated.

</pre>
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