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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [SimplifyCFGPass] mergeEmptyReturnBlocks() leaves broken callbr (asm goto) instruction."
href="https://bugs.llvm.org/show_bug.cgi?id=45062">45062</a>
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<th>Summary</th>
<td>[SimplifyCFGPass] mergeEmptyReturnBlocks() leaves broken callbr (asm goto) instruction.
</td>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>paulsson@linux.vnet.ibm.com
</td>
</tr>
<tr>
<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=23188" name="attach_23188" title="reduced testcase">attachment 23188</a> <a href="attachment.cgi?id=23188&action=edit" title="reduced testcase">[details]</a></span>
reduced testcase
define void @j() {
bb:
callbr void asm sideeffect "", "X"(i8* blockaddress(@j, %bb4))
to label %bb13 [label %bb4]
bb4: ; preds = %bb
ret void
bb13: ; preds = %bb
ret void
}
-> /bin/opt ./tc_callbr.ll -simplifycfg
define void @j() {
bb:
callbr void asm sideeffect "", "X"(i8* blockaddress(@j, %bb4))
to label %bb4 [label %bb4]
bb4: ; preds = %bb, %bb
ret void
}
Duplicate callbr destination!
callbr void asm sideeffect "", "X"(i8* blockaddress(@j, %bb4))
to label %bb4 [label %bb4]
in function j
LLVM ERROR: Broken function found, compilation aborted!
Since a callbr is not allowed to have duplicate labels, the %bb4 argument and
indirect label must be removed but it is not done.
Perhaps SimplifyCFG should do this, or perhaps calling BB.replaceAllUsesWith()
should take care of this with a call similar to
BB->replaceSuccessorsPhiUsesWith()?</pre>
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