<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/84801>84801</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [SelectionDAGBuilder] Bad machine code: MBB has duplicate entries in its successor list.
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            crash-on-valid,
            llvm:SelectionDAG
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          JonPsson1
      </td>
    </tr>
</table>

<pre>
    SelectionDAGBuilder::visitSwitch()

```
cat tc_MBBlists.ll 
define void @fun(i32 %CC) {
  switch i32 %CC, label %2 [
    i32 0, label %2
    i32 8, label %2
  ]

2:
  ret void
}

llc -mtriple=s390x-linux-gnu -mcpu=z15 -O3 -disable-cgp-branch-opts -verify-machineinstrs ./tc_MBBlists.ll

*** Bad machine code: MBB has duplicate entries in its successor list. ***
- function:    fun
- basic block: %bb.0  (0x9a46ef8)

*** Bad machine code: MBB has duplicate entries in its predecessor list. ***
- function: fun
- basic block: %bb.1  (0x9a46ff8)
LLVM ERROR: Found 2 machine code errors.
```
@statham-arm ?
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJysVFGrrDYQ_jXjyxCJUVd98GE91kK5h1vOhb6WJGbXtDGRJG7P7a8vut6ySw-00AtBGb4vk2-Gb4aHoK9WqRbKDso-4WucnG9_cvbnEJzNEuHGr-0XZZSM2tn-_GO3ajMqD_kZ8vNNBx2__KGjnIDVwBqgPdDz8T3R4-yh5BGj_PW164wOMaTG4B0Y1UVbhTenR4SCXlYLrNY5Q2DlywuwBqHq7lTEsD-GD_ALGi6U2UKGWxkHE3cSfSY8g_XHIJT9Yx1sq_WAvIq70AOvnojGSCRz9HoxCvI-5A19J0bb9Z1c7YpklssKef9nViL5nCMZdeDCKCKvCxGeWzkRt8SA5Ka8vnwlM5eTtkrbEH3AFNjw3L-nZrPjYMdHPG6idKOC_IyvXYcTDziui9GSR4XKRq9VQG1Rx4BhlVKF4DxuyVP8O909O8HLancHbNkQt_AbInjQEoVx8vcNBFYKkVJEYDV9b3hxUpd_OOP_iV28GtV_l_tvWrMHrZcHrZ8-_fKKP7y9fX7buINb7YjsSS0q750P6Yd-h4KGyOPEZ8L9jJAPydjmY5M3PFFtVmU0qxpaNMnUZqdGFkJUZaFEKZq6yIuxkKrJT7WoqoonumWUFTTPsqwqClqlJ5lRxkpVNzWVgo1QUDVzbVJjbnPq_DXRIayqrYuaZslu8bDPOGPS8zARZ8mNGz0CY8BegLHtIuTnx1HfsLJPfLthRKzXAAX9Zr7jmaij2bfHRzui7L-LG5PVm3aKcQnbJLIB2HDVcVpFKt0MbNil339k8e43JSOwYW9AADbsPfgrAAD__znfdUs">