<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/144301>144301</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            PDB shows wrong calling convention when compiling static functions on Windows x86
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          momo5502
      </td>
    </tr>
</table>

<pre>
    Compiling the following sample for Windows x86 with -O3 shows that `static_func` will have `fastcc` applied to it:

```C++
static __declspec(noinline) int static_func(int arg1){
        
        return arg1 * 2;
}

int main(int argc, char* argv[]) {
        return static_func(argc);
}
```

https://godbolt.org/z/Pcroj66c4

The PDB however shows `NearC`, so cdecl, instead of `FastCall`.

The reason this happens is because GlobalOpt updates the CC, but not the debug info:

https://github.com/llvm/llvm-project/blob/aa8a1fa6f515f45db55365b9c1f8453ded24ed32/llvm/lib/Transforms/IPO/GlobalOpt.cpp#L2022

I feel like the `DISubroutineType` should be updated to `DW_CC_BORLAND_msfastcall` for Windows x86. So that the PDB depicts the correct CC.
</pre>
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