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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [ScalarEvolution] Iteration order over Set depends on pointer values"
href="https://llvm.org/bugs/show_bug.cgi?id=26816">26816</a>
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<th>Summary</th>
<td>[ScalarEvolution] Iteration order over Set depends on pointer values
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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
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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>Global Analyses
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>mattias.v.eriksson@ericsson.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>I am seeing some non-deterministic behavior in the output files in some tests
that I am running.
I have been tracking the problem and I think it is caused by a new for loop in
ScalarEvolutionExpander. The iteration order over Set below will depend on
pointer values. I am not sure how to fix this.
Value *SCEVExpander::FindValueInExprValueMap(const SCEV *S,
const Instruction *InsertPt) {
SetVector<Value *> *Set = SE.getSCEVValues(S);
// If the expansion is not in CanonicalMode, and the SCEV contains any
// sub scAddRecExpr type SCEV, it is required to expand the SCEV literally.
if (CanonicalMode || !SE.containsAddRecurrence(S)) {
// If S is scConstant, it may be worse to reuse an existing Value.
if (S->getSCEVType() != scConstant && Set) {
// Choose a Value from the set which dominates the insertPt.
// insertPt should be inside the Value's parent loop so as not to break
// the LCSSA form.
for (auto const &Ent : *Set) {</pre>
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