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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - SCEV/IndVars has quadratic compile time complexity"
href="https://bugs.llvm.org/show_bug.cgi?id=50384">50384</a>
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<th>Summary</th>
<td>SCEV/IndVars has quadratic compile time complexity
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
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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>
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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>Transformation Utilities
</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>lebedev.ri@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<pre>Created <span class=""><a href="attachment.cgi?id=24863" name="attach_24863" title="n=32">attachment 24863</a> <a href="attachment.cgi?id=24863&action=edit" title="n=32">[details]</a></span>
n=32
I have not fully assessed what is going on, but -indvars, clearly,
scales non-linearly with the IR size.
<a href="https://www.wolframalpha.com/input/?i=fit+%7B32%2C+0.2114%7D%2C%7B64%2C+0.4191%7D%2C%7B128%2C+1.3613%7D%2C%7B256%2C+4.7540%7D%2C%7B512%2C+17.7136%7D%2C%7B1024%2C+74.2987%7D">https://www.wolframalpha.com/input/?i=fit+%7B32%2C+0.2114%7D%2C%7B64%2C+0.4191%7D%2C%7B128%2C+1.3613%7D%2C%7B256%2C+4.7540%7D%2C%7B512%2C+17.7136%7D%2C%7B1024%2C+74.2987%7D</a>
Where x is LoopMicroOpBufferSize in X86ScheduleZnver3.td
(aka the desired unrolled loop size), and y is the time -indvars takes.
As it stands right now, i've put myself into a corner,
and with -march=znver3 it is simply unfeasible
to compile e.g. vanilla test-suite, it just takes too long.</pre>
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