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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Miscompilation in ARM backend"
href="http://bugs.llvm.org/show_bug.cgi?id=32658">32658</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Miscompilation in ARM backend
</td>
</tr>
<tr>
<th>Product</th>
<td>tools
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>Other
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>llc
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>jlerouge@apple.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=18285" name="attach_18285" title="Reduced test case">attachment 18285</a> <a href="attachment.cgi?id=18285&action=edit" title="Reduced test case">[details]</a></span>
Reduced test case
I have been chasing a miscompilation for the past few days, ended up reducing
it to the attached bitcode.
(Update the triple for your arm platform, I have been able to repro with
thumbv7-apple-ios9.0.0 or armv7-none-linux-androideabi)
Repro steps:
$ llc -O0 -relocation-model=pic -disable-fp-elim -o main.good.s repro.ll
$ clang -arch armv7 -o main.good main.good.s
Execute on your favorite iOS/Android armv7 device:
$ ./main.good
$ echo $?
0
$ llc -O1 -relocation-model=pic -disable-fp-elim -o main.bad.s repro.ll
$ clang -arch armv7 -o main.bad main.bad.s
Execute on your favorite iOS/Android armv7 device:
$ ./main.bad
$ echo $?
2
>From what I can tell, the fist byte of the arg buffer should be set to 0 after
the test, but in the bad case, it seems like we end up writing at offset 16
(which in the larger test where this was reduced from was causing a very nasty
corruption).
On that specific test, git bisect seems to say that the regression was
introduced by r250129, but I suspect that change is merely exposing a bug that
was already present somewhere else down the pipe.</pre>
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