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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - DAGCombiner: UNREACHABLE "Operand not processed?""
href="https://bugs.llvm.org/show_bug.cgi?id=36588">36588</a>
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<th>Summary</th>
<td>DAGCombiner: UNREACHABLE "Operand not processed?"
</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>
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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>enhancement
</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>paulsson@linux.vnet.ibm.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<pre>Created <span class=""><a href="attachment.cgi?id=19993" name="attach_19993" title="reduced testcase">attachment 19993</a> <a href="attachment.cgi?id=19993&action=edit" title="reduced testcase">[details]</a></span>
reduced testcase
A small, reduced csmith program seems to expose some bug in DAGCombiner where a
brcond gets incorrectly combined:
=== main
Initial selection DAG: %bb.0 'main:'
SelectionDAG has 16 nodes:
t2: ch = seteq
t6: i1 = setcc undef:i32, Constant:i32<0>, setne:ch
t7: i1 = or t6, Constant:i1<-1>
t0: ch = EntryToken
t8: i32 = any_extend t7
t10: ch = CopyToReg t0, Register:i32 %0, t8
t11: i1 = xor t7, Constant:i1<-1>
t13: ch = brcond t10, t11, BasicBlock:ch< 0x28c29288>
t15: ch = br t13, BasicBlock:ch<.preheader 0x28c29108>
Optimized lowered selection DAG: %bb.0 'main:'
SelectionDAG has 8 nodes:
t0: ch = EntryToken
t10: ch = CopyToReg t0, Register:i32 %0, Constant:i32<1>
t17: ch = brcond t10, t17, BasicBlock:ch< 0x28c29288>
t15: ch = br t17, BasicBlock:ch<.preheader 0x28c29108>
Operand not processed?
t15: ch = br t17, BasicBlock:ch<.preheader 0x28c29108>
---
Initial selection DAG: %bb.0 'main:'
SelectionDAG has 16 nodes:
t2: ch = seteq
t6: i1 = setcc undef:i32, Constant:i32<0>, setne:ch
t7: i1 = or t6, Constant:i1<-1>
t0: ch = EntryToken
t8: i32 = any_extend t7
t10: ch = CopyToReg t0, Register:i32 %0, t8
t11: i1 = xor t7, Constant:i1<-1>
t13: ch = brcond t10, t11, BasicBlock:ch< 0x36a3afd8>
t15: ch = br t13, BasicBlock:ch<.preheader 0x36a3ae58>
Combining: t15: ch = br t13, BasicBlock:ch<.preheader 0x36a3ae58>
Combining: t14: ch = BasicBlock<.preheader 0x36a3ae58>
Combining: t13: ch = brcond t10, t11, BasicBlock:ch< 0x36a3afd8>
Replacing.2 t11: i1 = xor t7, Constant:i1<-1>
With: t16: i1 = Constant<0>
... into: t17: ch = brcond t10, t17, BasicBlock:ch< 0x36a3afd8>
...
After first time in visitBRCOND(), the CC i1 becomes constant, and then things
seem to go wrong. t17 is then using itself which is impossible.
---
bin/llc -mtriple=s390x-linux-gnu -mcpu=z13 tc_isel.ll -o out.s -O3</pre>
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