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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [ScalarEvolution] createNodeForGEP over-optimistic about preserving nsw"
href="https://llvm.org/bugs/show_bug.cgi?id=23527">23527</a>
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<th>Summary</th>
<td>[ScalarEvolution] createNodeForGEP over-optimistic about preserving nsw
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<th>Product</th>
<td>libraries
</td>
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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>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Global Analyses
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>wujingyue@gmail.com
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</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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</tr></table>
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<pre>[Copied from llvmdev@]
I was looking at ScalarEvolution::createNodeForGEP
(<a href="http://llvm.org/docs/doxygen/html/ScalarEvolution_8cpp_source.html#l03702">http://llvm.org/docs/doxygen/html/ScalarEvolution_8cpp_source.html#l03702</a>),
and noticed that the code that applies nsw flags to the resultant SCEV is
inconsistent with the comment.
While the comment says
03709 // Don't blindly transfer the inbounds flag from the GEP instruction to
the
03710 // Add expression, because the Instruction may be guarded by control
flow
03711 // and the no-overflow bits may not be valid for the expression in any
03712 // context.
03713 SCEV::NoWrapFlags Wrap = GEP->isInBounds() ? SCEV::FlagNSW :
SCEV::FlagAnyWrap;
the code still transfers nsw to LocalOffset and BaseS+TotalOffset.</pre>
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