<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/130958>130958</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Clang] Missed case of TBAA with different derived classes with a common base class
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:codegen,
            missed-optimization,
            TBAA
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          frederick-vs-ja
      </td>
    </tr>
</table>

<pre>
    When compiling this example with `-O3`, Clang currently performs one more indirection than GCC. [Godbolt link](https://godbolt.org/z/hKd7561os)

```C++
struct Base {
  int x;
};

struct D1 : Base {};

struct D2 : Base {
  Base y;
};

int foo2(D1& d1, D2& d2) {
  d1.x = 1;
  d2.x = 2;
  return d1.x;
}
```

It seems that Clang's TBAA can be improved for such cases.
</pre>
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