Index: lib/CodeGen/IslNodeBuilder.cpp
===================================================================
--- lib/CodeGen/IslNodeBuilder.cpp
+++ lib/CodeGen/IslNodeBuilder.cpp
@@ -358,11 +358,17 @@
 
   auto *NewAccesses = createNewAccesses(Stmt, User);
   createSubstitutionsVector(Expr, Stmt, VLTS, IVS, IteratorID);
-  VectorBlockGenerator::generate(BlockGen, *Stmt, VLTS, S, NewAccesses);
+
+  if (Stmt->isRegionStmt())
+    createUser(User);
+  else {
+    VectorBlockGenerator::generate(BlockGen, *Stmt, VLTS, S, NewAccesses);
+    isl_ast_node_free(User);
+  }
+
   isl_id_to_ast_expr_free(NewAccesses);
   isl_map_free(S);
   isl_id_free(Id);
-  isl_ast_node_free(User);
 }
 
 void IslNodeBuilder::createMark(__isl_take isl_ast_node *Node) {
Index: test/Isl/CodeGen/region-vec-fallback.ll
===================================================================
--- test/Isl/CodeGen/region-vec-fallback.ll
+++ test/Isl/CodeGen/region-vec-fallback.ll
@@ -0,0 +1,49 @@
+; RUN: opt %loadPolly -polly-vectorizer=polly -polly-codegen -S < %s
+;
+; Check that we do not crash while attempting to vectorize a region stmt.
+;
+; CHECK : polly.start
+;
+source_filename = "bugpoint-output-4e649ba.bc"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: nounwind uwtable
+define void @calcfreq_nuc(double* %datafreq) #0 {
+entry:
+  br label %for.body
+
+for.cond1.preheader:                              ; preds = %for.body
+  br label %for.body37
+
+for.body:                                         ; preds = %for.body, %entry
+  br i1 undef, label %for.body, label %for.cond1.preheader
+
+for.cond49.preheader:                             ; preds = %for.inc46
+  ret void
+
+for.body37:                                       ; preds = %for.inc46, %for.cond1.preheader
+  %indvars.iv116 = phi i64 [ 0, %for.cond1.preheader ], [ %indvars.iv.next117, %for.inc46 ]
+  %arrayidx39 = getelementptr inbounds double, double* %datafreq, i64 %indvars.iv116
+  %cmp40 = fcmp olt double undef, 1.000000e-04
+  br i1 %cmp40, label %if.then42, label %for.inc46
+
+if.then42:                                        ; preds = %for.body37
+  store double 1.000000e-04, double* %arrayidx39, align 8, !tbaa !1
+  br label %for.inc46
+
+for.inc46:                                        ; preds = %if.then42, %for.body37
+  %indvars.iv.next117 = add nuw nsw i64 %indvars.iv116, 1
+  %exitcond118 = icmp ne i64 %indvars.iv.next117, 4
+  br i1 %exitcond118, label %for.body37, label %for.cond49.preheader
+}
+
+attributes #0 = { nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.ident = !{!0}
+
+!0 = !{!"clang version 5.0.0 "}
+!1 = !{!2, !2, i64 0}
+!2 = !{!"double", !3, i64 0}
+!3 = !{!"omnipotent char", !4, i64 0}
+!4 = !{!"Simple C/C++ TBAA"}