[Polly] Move ScopStmt::getSchedule to islpp. NFC.

[grosser]

Thank you Nandini! I committed this and D36659.

lib/Analysis/ScopInfo.cpp

   isl::set AccDom = getLatestAccessRelation().domain();
 
   return isl_set_is_subset(StmtDom.keep(), AccDom.keep()) == isl_bool_false;
 }
 
 //===----------------------------------------------------------------------===//
 
 isl::map ScopStmt::getSchedule() const {
-  isl_set *Domain = getDomain().release();
-  if (isl_set_is_empty(Domain)) {
-    isl_set_free(Domain);
-    return isl::manage(isl_map_from_aff(isl_aff_zero_on_domain(
-        isl_local_space_from_space(getDomainSpace().release()))));
-  }
-  auto *Schedule = getParent()->getSchedule().release();
-  if (!Schedule) {
-    isl_set_free(Domain);
+  isl::set Domain = getDomain();
+  if (Domain.is_empty())
+    return isl::map::from_aff(isl::aff(isl::local_space(getDomainSpace())));
+  auto Schedule = getParent()->getSchedule();
+  if (!Schedule)
     return nullptr;
-  }
-  Schedule = isl_union_map_intersect_domain(
-      Schedule, isl_union_set_from_set(isl_set_copy(Domain)));
-  if (isl_union_map_is_empty(Schedule)) {
-    isl_set_free(Domain);
-    isl_union_map_free(Schedule);
-    return isl::manage(isl_map_from_aff(isl_aff_zero_on_domain(
-        isl_local_space_from_space(getDomainSpace().release()))));
-  }
-  auto *M = isl_map_from_union_map(Schedule);
-  M = isl_map_coalesce(M);
-  M = isl_map_gist_domain(M, Domain);
-  M = isl_map_coalesce(M);
-  return isl::manage(M);
+  Schedule = Schedule.intersect_domain(isl::union_set(Domain));
+  if (Schedule.is_empty())
+    return isl::map::from_aff(isl::aff(isl::local_space(getDomainSpace())));
+  isl::map M = M.from_union_map(Schedule);
+  M = M.coalesce();
+  M = M.gist_domain(Domain);
+  M = M.coalesce();
+  return M;
 }
 
 void ScopStmt::restrictDomain(isl::set NewDomain) {
   assert(NewDomain.is_subset(Domain) &&
          "New domain is not a subset of old domain!");
   Domain = NewDomain;
 }