<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/88233>88233</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            llvm:SelectionDAG: memory leak caused by static std::set EVTs
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

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

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

<pre>
    Hi!

We're using LLVM for jit compilation in our in-memory database, therefore memory handling is crucial. While switching from llvm 13 to 18 we saw that the std::set EVTs causes a memory leak in SDNode::getValueTypeList(). As far as I understand the code, for each extended EVT (we're using i96) a new value is inserted to the set if the pointer of the Type is different. An this does happen for identical types, if the compilation is done with a new instance of the llvm classes.

A possible fix for this leak would be to make EVTs a member of SelectionDAG. However, SDNode::getValueTypeList() has no access to the SelectionDAG instance, and passing EVTs as parameter would require many further changes, since getValueTypeList is called from SDNode::getSDVTList() and this is called in many locations, also outside of SelectionDAG.

What can we do to close this memory leak?

@nhaehnle, you switched EVTs from a managed static to a local static. Do you know how to handle the situation in a better way?
</pre>
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