<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/116697>116697</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [NVPTX] Lower `dynamic_stackallloc` in Instruction Selection instead of Operation Legalization
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            good first issue,
            backend:NVPTX
      </td>
    </tr>

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

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

<pre>
    Currently, we [lower `dynamic_stackalloc` during operation legalization](https://github.com/llvm/llvm-project/blob/e0b522dd94e48229d587a54a3103ba1c198b16a7/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp#L2275-L2304). However, if we are okay with losing the friendlier error message we could decare this operation as legal and handle is during [instruction selection](https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/NVPTX/NVPTXInstrInfo.td).

This would require declaring [`ISD::DYNAMIC_STACKALLOC`](https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/CodeGen/ISDOpcodes.h#L1105-L1112) in [`TargetSelectionDAG.td`](https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/Target/TargetSelectionDAG.td) and lowering it in [NVPTXInstrInfo.td](https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/NVPTX/NVPTXInstrInfo.td)
</pre>
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