[polly] Change SmallPtrSet which are being iterated into SmallSetVector

Summary: Otherwise the lack of an iteration order results in non-determinism in codegen.

Reviewers: _jdoerfert, zinob, grosser

Tags: #polly

Differential Revision: https://reviews.llvm.org/D25863

llvm-svn: 284845

polly/lib/Analysis/ScopInfo.cpp

@@ -2978,7 +2978,7 @@ bool Scop::buildAliasGroups(AliasAnalysis &AA) {
   }
 
   auto &F = getFunction();
-  MapVector<const Value *, SmallPtrSet<MemoryAccess *, 8>> ReadOnlyPairs;
+  MapVector<const Value *, SmallSetVector<MemoryAccess *, 8>> ReadOnlyPairs;
   SmallPtrSet<const Value *, 4> NonReadOnlyBaseValues;
   for (AliasGroupTy &AG : AliasGroups) {
     NonReadOnlyBaseValues.clear();