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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - "Simplify the CFG" pass moves musttail call from tail position"
href="https://bugs.llvm.org/show_bug.cgi?id=35774">35774</a>
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<th>Summary</th>
<td>"Simplify the CFG" pass moves musttail call from tail position
</td>
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>5.0
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
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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
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<th>Component</th>
<td>Transformation Utilities
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>benzrf@gmail.com
</td>
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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=19611" name="attach_19611" title="Files mentioned in the description">attachment 19611</a> <a href="attachment.cgi?id=19611&action=edit" title="Files mentioned in the description">[details]</a></span>
Files mentioned in the description
The attached file `musttail.ll` branches before making a call. The callee is
the same in both branches, but it is a non-tail call in one branch and a
`musttail` call in the other. The optimizer mistakenly merges the two calls
into a single one before the branch, resulting in incorrect output. Running
`clang -O1 -S -emit-llvm musttail.ll -o musttail_O1.ll` produces an attached
malformed file which is rejected by `llc` for containing a `musttail` call in
non-tail position. I have also attached the output of `opt -O1 -S
-print-after-all musttail.ll`.</pre>
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