Index: polly/trunk/lib/CodeGen/IslAst.cpp
===================================================================
--- polly/trunk/lib/CodeGen/IslAst.cpp
+++ polly/trunk/lib/CodeGen/IslAst.cpp
@@ -400,6 +400,14 @@
   bool PerformParallelTest = PollyParallel || DetectParallel ||
                              PollyVectorizerChoice != VECTORIZER_NONE;
 
+  // We can not perform the dependence analysis and, consequently,
+  // the parallel code generation in case the schedule tree contains
+  // extension nodes.
+  auto *ScheduleTree = S->getScheduleTree();
+  PerformParallelTest =
+      PerformParallelTest && !S->containsExtensionNode(ScheduleTree);
+  isl_schedule_free(ScheduleTree);
+
   // Skip AST and code generation if there was no benefit achieved.
   if (!benefitsFromPolly(S, PerformParallelTest))
     return;