SLPVectorizer: Use properlyDominates to satisfy the irreflexivity of a strict weak ordering.

STL debug mode checks this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194015 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -1626,7 +1626,7 @@ class DTCmp {
 public:
   DTCmp(const DominatorTree *DT) : DT(DT) {}
   bool operator()(const BasicBlock *A, const BasicBlock *B) const {
-    return DT->dominates(A, B);
+    return DT->properlyDominates(A, B);
   }
 };