<html>
<head>
<base href="https://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - optnone function results in MachineBasicBlocks with duplicated predecessors"
href="https://llvm.org/bugs/show_bug.cgi?id=24581">24581</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>optnone function results in MachineBasicBlocks with duplicated predecessors
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</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>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>matze@braunis.de
</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>The machine verifier enforces the property that no block is listed twice in the
successor or predecessor list. For a function with the optnone function this is
not always true after instruction selection. Example:
<span class="quote">> cat test.ll</span >
define void @bar() #0 {
entry:
br i1 undef, label %exit, label %exit
exit:
ret void
}
attributes #0 = { noinline optnone }
<span class="quote">> llc -verify-machineinstrs test.ll</span >
...
*** Bad machine code: MBB has duplicate entries in its successor list. ***
...
I'm not sure why the machine verifier enforces this property, without the
optnone attribute the codegenprepare appears to remove those pointless jumps
though I am not sure yet whether this is on purpose to avoid the verification
problems.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>