<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/64632>64632</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] -msse2, -mavx, (etc) do not fail when not supported by the target
        </td>
    </tr>

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

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

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

<pre>
    on aarch64:  
clang: 

```console
/ # clang main.c -msse2
clang-16: warning: argument unused during compilation: '-msse2' [-Wunused-command-line-argument]
```

gcc:
```console
/ # gcc main.c -msse2
gcc: error: unrecognized command-line option '-msse2'
```

i don't know which one is actually meant to be correct. but for configure tests that don't use -Werror ([like here](https://github.com/kdave/btrfs-progs/blob/bb0ca35245858f17a6ced97aade1dd8d70f9c9d7/configure.ac#L52)) this makes the build system think this is actually supported, and later sets a define that isn't actually then valid.

that's perhaps weird use (i never found other breakage aside from this case, so i assume usually one tests such things slightly differently or at least paired with Werror), but this specific -m value use doesn't seem like it has value being ignored instead of hard-failing?

the challenge here is disambiguating "-msse not used for some reason on x86_64 where it exists" and "-msse not used because platform doesn't have it whatsoever (different -m args for platform simd entirely)"
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJyMVE3P4yYQ_jXkMkrk4PjrkMPuvsqp9z1WYxjbNBgsBidv-usrcDbNttWqUhSDDQ_PBzPIbEZHdBbVV1F97HCNkw9nR1e_8OPqmXa914-zd4AY1FSfRPkFQBQfoviiLLoxzbfp878utp_yjr2l51t5ASFLyFtgRuMOCvYzM8k3rP2xTnB3DM5syBjGdSYXYXUrkwa9BuNGUH5ejMVovMvny-aJJRsQ1df99235Xvl5Rqf31jja_8AS1cc_qL7zH5US5f_SMir1X0o2AKAQfEiD1QVSfnTmT9LwTgj8kgT8xP4XxAxo74RsIlydv8N9MmoC7wgMA6q4orUPmAldhOihJ1A-BFLxAP0aYfABlHeDGddAEIkjQ5wwvkBXJth_z6xByFZUX625EkwUKBkm2ynGhZM18iLkZTRxWvuD8rOQl6vGGwl56WMYeL8EP3KaWd-nR18oLCt5qtqqHY4N1op01yBqOmrd6qYYOtXpRsjLi-ABlZDlb5UUshOygzgZhhmvlEgT9KuxGvjBkeb0zV23Fe9O8LosPkTSQn4DdBosRgrAFBkQNA0pgeyA4c2B19Y4kYMbWqMP7wGkxUI2DAuFCReGO5mgs3FCtgYc3SjA4FenwceJAvSB8IojAbLRBEPw80ZUIVPixR4MIPM6E6y8nZ4i3fLhVU1Z3sjA1oxTtA_QZhgokEtjHwAjWEKOsKAJpOFu4gRbjNm7bzn9fCgvpMxg0m1N6lbK1LWnp34mmiGHbiJMyM9FPaWKM6PzCd84joQa_AATBr0f0Nhcq5efrSJQE1pLbtzuUMpGG8a5N-OKMUEKKfO9B-fz9dP5krKfCQIhewfewWdb_16f4L5hRKBPw5GFlDnTf0P0pDDJWizGwYf5Td-EtwxxnzCyz2EJ2b78TLZgGDmzeG1nM2sgF00g-8iOyp0-l7orO9zR-Vh3x7ZoyqbdTeeuL5u-rxQWSp66Uydl3RSNqumI5VE2zc6cZSHLoj3KQsqubA9lrevqRHV1bNWxrQpxKmhGYw_W3uaDD-POMK90rk91KXcWe7KcW7WUju6QPwopU-cO57Rn368ji1Nhk0t_o0QTbe7xW8uuPn50LPkN9jPePtNAyJaiSuWmfTY0ZZucd3n2Kijoc4lAxDBS3K3Bnn_RGxKH5yN1hj9IRSEvmXlqElnZXwEAAP__oYEgRA">