<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/149018>149018</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Replace isSupportedInstr with RISCVII:elementsDependOnVL in RISCVVLOptimizer
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            backend:RISC-V
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          lukel97
      </td>
    </tr>
</table>

<pre>
    RISCVII::elementsDependOnVL uses TS flags defined in tablegen to determine if it's safe to reduce the VL of a pseudo, and RISCVVectorPeephole already uses it in it's implementation of VL reduction. 

Now that we've added pretty much all pseudos to isSupportedInstr (#147647), we should look at reusing this. 

We need to make sure that other extension tablegen files have `ElementsDependOn` set correctly, e.g. RISCVInstrInfoXRivos.td, RISCVInstrInfoXSf.td, RISCVInstrInfoXSfmm.td, etc.
</pre>
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