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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Incorrect result with -O1 -march=skx"
href="https://bugs.llvm.org/show_bug.cgi?id=32311">32311</a>
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<th>Summary</th>
<td>Incorrect result with -O1 -march=skx
</td>
</tr>
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<th>Product</th>
<td>new-bugs
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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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>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>Vsevolod.Livinskij@frtk.ru
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<pre>Created <span class=""><a href="attachment.cgi?id=18112" name="attach_18112" title="Reproducer.">attachment 18112</a> <a href="attachment.cgi?id=18112&action=edit" title="Reproducer.">[details]</a></span>
Reproducer.
Clang produces wrong code with -O1/2/3 -march=skx options.
According to LLVM bisect, it is a fault of X86 DAG->DAG Instruction Selection
(as far as I understood its output).
BISECT: running pass (62) X86 DAG->DAG Instruction Selection on function
BISECT: NOT running pass (63) Local Dynamic TLS Access Clean-up on function
Unfortunately, I failed to reduce test case further.
Error:
<span class="quote">>$ clang++ -w -O0 -march=skx *.cpp
>$ sde -skx -- ./a.out</span >
1
<span class="quote">>$ clang++ -w -O1 -march=skx *.cpp
>$ sde -skx -- ./a.out </span >
-1
LLVM version:
clang version 5.0.0 (trunk 297835)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/vsevolod/workspace/llvm/bin-trunk/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6.0.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64</pre>
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