<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/57904>57904</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            The `v8a` feature should be enabled by default on aarch64
        </td>
    </tr>

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

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

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

<pre>
    The `TTBR0_EL2` register is [locked](https://github.com/llvm/llvm-project/blob/76fd4bf675b5ceeeca0e4e15cf15d89c7acf4947/llvm/lib/Target/AArch64/AArch64SystemOperands.td#L920) behind `el2vmsa` when it should be available on all aarch64 platforms. This has been [noticed](https://github.com/rust-lang/rust/issues/97724) in Rust which does not currently enable the feature by default or expose a stable way to enable it, though I feel here is a better place to solve the issue.

The `v8a` [feature](https://github.com/llvm/llvm-project/blob/76fd4bf675b5ceeeca0e4e15cf15d89c7acf4947/llvm/lib/Target/AArch64/AArch64.td#L496), added about a year ago, seems to want to represent features enabled on ARM v8.0 processors, but these features should really be enabled by default if this is the case.
</pre>
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