<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/154113>154113</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Clang] Add __builtin_elementwise_ctlz/cttz builtin intrinsics
        </td>
    </tr>

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

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

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

<pre>
    Implement vector elementwise leading/trailing zero count intrinsics with constexpr support - references #153113 + #153572

I know a the very least AVX512 / NEON both correctly handle the zero input case so I don't believe we need the "is_zero_poison" handling like we do for the llvm intrinsic. 
</pre>
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