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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Bad PHI node after loop distribute"
href="https://llvm.org/bugs/show_bug.cgi?id=28037">28037</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Bad PHI node after loop distribute
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<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>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>mikael.holmen@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=16486" name="attach_16486" title="Reproducer ll file">attachment 16486</a> <a href="attachment.cgi?id=16486&action=edit" title="Reproducer ll file">[details]</a></span>
Reproducer ll file
We've stumled upon a case where loop-distribute produces wrong code:
opt -loop-distribute loopdistbad.ll
gives
PHINode should have one entry for each predecessor of its parent basic block!
%split = phi i16 [ undef, %bb6 ]
LLVM ERROR: Broken function found, compilation aborted!
It's after LoopVersioning that the code looks bad. Specifically after the call
to
LVer.versionLoop(DefsUsedOutside);
Before bb5.bb7_crit_edge looks like:
bb5.bb7_crit_edge: ; preds = %bb6
%_tmp142.lcssa = phi i16 [ %_tmp142, %bb6 ]
%split = phi i16 [ %_tmp12114, %bb6 ]
store i16 %_tmp142.lcssa, i16* %k.19
br label %bb7
and after:
bb5.bb7_crit_edge: ; preds = %bb6.lver.orig, %bb6
%_tmp142.lcssa = phi i16 [ %_tmp142, %bb6 ], [ %_tmp142.lver.orig,
%bb6.lver.orig ]
%split = phi i16 [ %_tmp12114, %bb6 ]
store i16 %_tmp142.lcssa, i16* %k.19
br label %bb7
The PHI
%_tmp142.lcssa = phi i16 [ %_tmp142, %bb6 ]
is rewritten by LoopVersioning::addPHINodes to add the new incoming edge, but
DefsUsedOutside doesn't contain the other PHI so that one isn't rewritten and
thus is left in a bad state.</pre>
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