diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -986,6 +986,13 @@
       std::array<std::pair<Value *, int>, 2> Values = {{LHS, RHS}};
       for (int Idx = 0, IdxE = Values.size(); Idx != IdxE; ++Idx) {
         Value *V = Values[Idx].first;
+        if (isa<ConstantData>(V)) {
+          // Walking the use list of a Constant (particularly, ConstantData)
+          // is not scalable, since a given constant may be used by many
+          // instructinos in many functions in many modules.
+          continue;
+        }
+
         // Calculate the absolute lane, using the minimum relative lane of LHS
         // and RHS as base and Idx as the offset.
         int Ln = std::min(LHS.second, RHS.second) + Idx;