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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Floating point constants are not deterministic across platforms"
href="https://llvm.org/bugs/show_bug.cgi?id=24859">24859</a>
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<th>Summary</th>
<td>Floating point constants are not deterministic across platforms
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>3.7
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
</tr>
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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>
</tr>
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<th>Component</th>
<td>LLVM Codegen
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>ed@80386.nl
</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=14896" name="attach_14896" title="Tarball with testcase and output">attachment 14896</a> <a href="attachment.cgi?id=14896&action=edit" title="Tarball with testcase and output">[details]</a></span>
Tarball with testcase and output
If I install exactly the same version of Clang (3.7.0-RELEASE) on Mac OS X,
FreeBSD and Linux, all targeting the same platform (x86_64-unknown-cloudabi)
and build the same source file at different optimization levels, I get
different results. This bug is similar in nature to <a class="bz_bug_link
bz_status_NEW "
title="NEW --- - LLVM/Clang 3.7.0 become undeterministic at >= -O1"
href="show_bug.cgi?id=24734">bug 24734</a>, but the root
cause is different. My suspicion is that this is related to FPU rounding modes.
Attached is a tarball that contains a C source file, foo.c, that is a reduced
testcase based on libspeex's vbr.c. This testcase has been built on Mac OS X,
FreeBSD and Linux, using different optimization modes. As you can see, anything
above -O0 yields different results.</pre>
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