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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [SCEV] Enormous SCEV growth on linear calculations"
href="https://bugs.llvm.org/show_bug.cgi?id=40292">40292</a>
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<th>Summary</th>
<td>[SCEV] Enormous SCEV growth on linear calculations
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<th>Product</th>
<td>new-bugs
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>new bugs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>max.kazantsev@azul.com
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=21316" name="attach_21316" title="simple.ll">attachment 21316</a> <a href="attachment.cgi?id=21316&action=edit" title="simple.ll">[details]</a></span>
simple.ll
The attached file demonstrates a corner case that makes SCEV hang. opt
-loop-vectorize -S works "infinitely" on this test due to huge SCEV creation.
Sometimes I observe crashes by stack overflow that seem to also be caused by
attempts to create huge SCEVs. Also reproducible with opt -analyze
-scalar-evolution (so it is not something specific for vectorizer).
This is a typical scenario of linear calculations with powers that come from
unrolled loops. We used to face problems of this variety in the past. Maybe
it's time to add some mechanism to restrict SCEV from doing any attempts of
simplifications here. Limiting by depth doesn't seem sufficient.</pre>
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