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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - MachineCodeSink Is Incorrect for SetJmp/LongJmp with Spill"
href="https://llvm.org/bugs/show_bug.cgi?id=28068">28068</a>
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<th>Summary</th>
<td>MachineCodeSink Is Incorrect for SetJmp/LongJmp with Spill
</td>
</tr>
<tr>
<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>Common Code Generator Code
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>wmoses@mit.edu
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=16500" name="attach_16500" title="Sample Case for the bug">attachment 16500</a> <a href="attachment.cgi?id=16500&action=edit" title="Sample Case for the bug">[details]</a></span>
Sample Case for the bug
I've come across a bug in MachineSink for
llvm.eh.sjlj.setjmp/llvm.eh.sjlj.longjmp. The bug occurs when an instruction is
sunk past a setjmp and the instruction later needs to be spilled.
The attached C code illustrates an example of this error when run with the
following flags to clang/opt/llc.
clang -O0 test.c -S -emit-llvm -o bad.ll
opt -mem2reg bad.ll -S -o bad2.ll
llc -O1 bad2.ll -o bad2.s
clang bad2.s -o bad2.o
./bad2.o
The expected output of the program should be four "0"'s, however the actual
output is two "0"'s followed by two "-1"'s.
In the attached example, MachineSink effectively moves x-- past the setjmp.
Because this value is spilled, the register value (as stored inside the stack)
is not restored to the value beforehand -- resulting in the decrement occuring</pre>
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