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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Using -exhaustive-register-search may lead to assert (RAGreedy)"
href="https://bugs.llvm.org/show_bug.cgi?id=38062">38062</a>
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<th>Summary</th>
<td>Using -exhaustive-register-search may lead to assert (RAGreedy)
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<th>Product</th>
<td>new-bugs
</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
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<th>Status</th>
<td>NEW
</td>
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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>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>verena@codeplay.com
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</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>When using the option -exhaustive-register-search and a low (or default) value
of -lcr-max-interf you may get the assertion `(i == Size || Traits::stopLess(b,
start(i))) && "Overlapping insert".
This is due to RAGreedy::mayRecolorAllInterferences:
if (Q.collectInterferingVRegs(LastChanceRecoloringMaxInterference) >=
LastChanceRecoloringMaxInterference && !ExhaustiveSearch) {
DEBUG(dbgs() << "Early abort: too many interferences.\n");
CutOffInfo |= CO_Interf;
return false;
}
for (unsigned i = Q.interferingVRegs().size(); i; --i) {
...
If ExhaustiveSearch is set then we loop through the interfering registers to
recolour them. But if LastChanceRecoloringMaxInterference is set to a number
lower than the actual number of interferences then we only process (deallocate)
a subset. When we then allocate the original interval we have introduced an
illegal overlap.
I feel -exhaustive-register-search should imply -lcr-max-interf=inf or at least
print a useful error message. I'm guessing without assertions enabled this
might just lead to wrong codegen.
I'm afraid my target is custom, so I can't provide a test case.</pre>
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