<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/120167>120167</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Clang] Matrix types are currently not supported in constant evaluation
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:frontend,
            constexpr
      </td>
    </tr>

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

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

<pre>
    We support vector types, so supporting matrices as well would make sense, even though it sounds like it’d be quite a bit of work as it would probably involve adding a new `APValue` kind.

As an example, this (https://godbolt.org/z/WE84hhYvP):
```c++
template <typename T>
constexpr bool f() {
    T t = T();
    return true;
}

using M = int [[clang::matrix_type(4, 4)]];

static_assert(f<M>());
```
doesn’t work currently:
```console
<source>:9:15: error: static assertion expression is not an integral constant expression
    9 | static_assert(f<M>());
      |               ^~~~~~
<source>:3:11: note: non-literal type 'int __attribute__((matrix_type(4, 4)))' cannot be used in a constant expression
    3 |     T t = T();
      |           ^
<source>:9:15: note: in call to 'f<int __attribute__((matrix_type(4, 4)))>()'
    9 | static_assert(f<M>());
      |               ^~~~~~
```
</pre>
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