<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=http://email.email.llvm.org/c/eJylU1mP0zAQ_jXJy2ijHD02D3koXQErWIGAP-Bjkhh8VB6npf31TFKWLccbUhJ7Ys98h8cy6HP3ZcSIQIiOIAWQCIdAZKRFEEBOWAvoR-EVOvQJ-hDBhhNG4wdw6NThDGkUCQyBiigSaghTgtBzug3hAPIM73l81Ca4Ah4T0Bgmq2cko7mkUcLOyGlECB6v1U6C4BRNSujBCT8xjTMYf90UzWA8J6mgsYC3zOaIMav3YBJo0_cYOXnkTDS8P8LdB-IkHi4zy0NEYtgCsvIhK3fX72dkuZzwXbiDxeu_MaUDZc0uq1_zMwQtg01FiANHF36ravPUfvTv2ttCrM-J8yxOgBTqG3rNiIHtdHBiOgsZiUpMhC--gGLwiCoM3lxw1rFoZSOUIJylSfaUf_fC2OWcdLiu91dhxS2HN_v9jKknhbQ4RsLh4tayfc4rct01um1akYspjSF2R03cCDqfou3-UM60J1mo4Diw9vg83DHGV1SJQ0M0IfFk3azu63zs1m2F2163Za2VEvetWOmVlCsl-m3VSuxzKyRa6rL1q2z9kP8_pOnqsq7Lqm6rqt6sN8W2UbKqyqZUqJpKr7NViY7dK-Y68ynmsVtKymkgXrSGEr0sCr4Dg0d8ZphMskuw-_TE8TzZRTVuVhzAjgid5A6d7f15KW4vwz9uwq9G7SMHf_U-H_9vbZ4vcrtF6w_stT67>53482</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [ARM][AArch64] Assembly for memcpy created out a loop by LoopIdiom differs from the one that was in original code
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
      </td>
    </tr>

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

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

<pre>
    There seems to be possible a small enhancement for lowering memcpy that is created out of a loop by LoopIdiom. It should be identical to the one that was written manually in the original code. However, it differs when either -Os or -Oz is present. 

See an example
https://godbolt.org/z/116M9PnK9

It may be a backend problem with -Os because LoopIdiom can recognize it in that case, but it fails to do that for -Oz.

GCC produces the same code for that.
</pre>
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