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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - LICM is moving an fdiv instruction out from under a control dependence"
href="https://bugs.llvm.org/show_bug.cgi?id=40954">40954</a>
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<th>Summary</th>
<td>LICM is moving an fdiv instruction out from under a control dependence
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Loop Optimizer
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>eric.schweitz@pgroup.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=21560" name="attach_21560" title="reproducer of LICM moving an fdiv instruction">attachment 21560</a> <a href="attachment.cgi?id=21560&action=edit" title="reproducer of LICM moving an fdiv instruction">[details]</a></span>
reproducer of LICM moving an fdiv instruction
In the attached reproducer, the instruction %33 is control dependent upon the
branch in block L.LB2_498. When we run the following command,
% opt -licm bug.ll -o bug.llvm
and look at the output file, we see that the fdiv becomes %28 and has been
moved to block L.LB2_555, which is a predecessor of L.LB2_498. This code
motion introduces a floating-point exception into the flow path which was
previously guarded by the conditional branch.</pre>
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