<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/145335>145335</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [CostModel] TargetTransformInfoImplCRTPBase.getInstructionCost - move shuffle analysis into improveShuffleKindFromMask / target getShuffleCost
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            llvm:analysis
      </td>
    </tr>

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

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

<pre>
    As discussed on #144690 and #141634 - we're making too many assumptions about how length changing shuffles are legalized by the target. These need to be driven by the actual target implementations.

Additionally - like getInstructionCost - improveShuffleKindFromMask needs to be able to recognize a SK_PermuteSingleSrc class shuffle that has been miss-tagged as a SK_PermuteTwoSrc class.

CC @davemgreen @preames 

https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h#L1527-L1547
</pre>
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