<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/120775>120775</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [VectorCombine] Handle shuffle of selects
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            missed-optimization,
            llvm:transforms
      </td>
    </tr>

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

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

<pre>
    VectorCombine can't currently fold `shuffle(select(c0,t0,f0), select(c1,t1,f1)) -> select(shuffle(c0,c1),shuffle(t0,t1),shuffle(f0,f1))` - although foldShuffleToIdentity can fold some very basic cases.

This is trickier than foldShuffleOfBinops etc. as the default increase in instruction count will likely prevent basic fold from succeeding (from a cost:benefit), so we will need to just handle cases where at least one of the folded inner shuffles gets simplified away.
</pre>
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