<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/86549>86549</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] __builtin_clzg / __builtin_ctzg aren't usable in constexpr contexts
        </td>
    </tr>

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

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

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

<pre>
    These newly added builtins (#83431) can't used in `constexpr` contexts. https://godbolt.org/z/ebP4E7rqd

I'd like to be able to use them a la (#86531).  I think it's a quick fix to just add `Constexpr` to the `Attributes` for these in clang/include/clang/Basic/Builtins.td, but we should add some unit tests for this.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJxcUjtzpDwQ_DUimTIFw3MDAj8-qpx9weUuIc2CvFpkM6Pz49dfCe_6XJcgaKCnu6c1s5tXokE1d6p5yHSUJWzD6szJEuvoV0cbZ1OwH8OvhZhgpTf_AdpasjBF58WtDAp7hVVf1VWp8ABGrwo7gchkwa2g2sKElYXeXzbVFmDCKvQunMMi8sKqulU4KhznYKfgJQ_brHD8VDjS9H_9X7e9WlU8qOL26_qosLPg3YlAAkwEevL7bWQCWegMGry-imqbXVQO8AiyuPUEThR2DBpeozMnOLr39PNzZEm-ktr7n2olJNIE34psbopCnPBj2NILpmTReL0m0W41PlpSOF6RO83OpPMSVi5W4T1MUeCNgJcQvd3ncjgTxNUJCLHwhd9xntmhsofqoDMayq4sq_5wKLtsGVpjamOttkXXmwmPpqqbamp722KP2DSZG7DAuqiwKfuiKZu8aEo9Hbv22Jiq6HpSdUFn7Xzu_e9zyj1zzJGGvm3qQ-b1RJ73biDOIVg4uo0F9m8UosJ7hXgxen36jg4xNWobEvXNFGdWdeEdC_8dJk783r0vjuYBnp4upXoy_nMGheNPSD5n0Btd27XvPYV_nfndrCxufvinXE6WOOUmnBWOScHluHnZwjMZSctLvljhuNv_EwAA__8CnAE5">