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      <base href="https://llvm.org/bugs/" />
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - Reassociate removes call but preserves CG, asserts"
   href="https://llvm.org/bugs/show_bug.cgi?id=30784">30784</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Reassociate removes call but preserves CG, asserts
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>tools
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>opt
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>jesper.antonsson@ericsson.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=17486" name="attach_17486" title="Reduced ll file exposing the bug">attachment 17486</a> <a href="attachment.cgi?id=17486&action=edit" title="Reduced ll file exposing the bug">[details]</a></span>
Reduced ll file exposing the bug

The reassociate pass may remove a call and then falsely claim to preserve the
CG. This later leads to this assert at dead function removal:

opt: ../include/llvm/Analysis/CallGraph.h:184:
llvm::CallGraphNode::~CallGraphNode(): Assertion `NumReferences == 0 && "Node
deleted while references remain"' failed.

One simple fix is to set the variable MadeChange to true in
RecursivelyEraseDeadInsts() if operating on a CallInst. (However, the
preservation code acting on MadeChange has a comment indicating that even when
set to true it should preserve the CG, but currently it does not.)

The attached ll-file can be used to provoke the bug using:
 opt -inline -functionattrs -reassociate reassoc-reduced.ll

The attached file originates from our randomised csmith test suite, but was
reduced to a minimum before inclusion here. I was unable to reduce the command
line to a single pass one.</pre>
        </div>
      </p>
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