Index: lib/Transform/ScheduleOptimizer.cpp
===================================================================
--- lib/Transform/ScheduleOptimizer.cpp
+++ lib/Transform/ScheduleOptimizer.cpp
@@ -463,8 +463,10 @@
 ///
 /// @param IslMap The isl map to be modified.
 static __isl_give isl_map *circularShiftOutputDims(__isl_take isl_map *IslMap) {
-  auto InputDimsId = isl_map_get_tuple_id(IslMap, isl_dim_in);
   auto DimNum = isl_map_dim(IslMap, isl_dim_out);
+  if (DimNum == 0)
+    return IslMap;
+  auto InputDimsId = isl_map_get_tuple_id(IslMap, isl_dim_in);
   IslMap = isl_map_move_dims(IslMap, isl_dim_in, 0, isl_dim_out, DimNum - 1, 1);
   IslMap = isl_map_move_dims(IslMap, isl_dim_out, 0, isl_dim_in, 0, 1);
   return isl_map_set_tuple_id(IslMap, isl_dim_in, InputDimsId);
@@ -482,6 +484,9 @@
     isl_map_free(NewPartialSchedule);
     return false;
   }
+  assert(isl_map_dim(NewPartialSchedule, isl_dim_out) == 3 &&
+         "Each schedule dimension should be represented by a union piecewise"
+         "quasi-affine expression.");
   NewPartialSchedule = circularShiftOutputDims(NewPartialSchedule);
   if (containsMatrMult(NewPartialSchedule)) {
     isl_map_free(NewPartialSchedule);