ScheduleTreeElemThreadSpecificMarker: require isl::ctx in constructor

Since ScheduleTreeElemThreadSpecificMarker is now a subclass of
ScheduleTree, it needs an isl::ctx to construct the ScheduleTree.  It is
available in all callsites of the ScheduleTreeElemThreadSpecificMarker
constructor.  Pass it as an argument.

Author: ftynse

tc/core/polyhedral/schedule_tree.cc

@@ -304,8 +304,8 @@ std::unique_ptr<ScheduleTree> ScheduleTree::makeExtension(
 std::unique_ptr<ScheduleTree> ScheduleTree::makeThreadSpecificMarker(
     isl::ctx ctx,
     std::vector<ScheduleTreeUPtr>&& children) {
-  auto res =
-      std::unique_ptr<ScheduleTree>(new ScheduleTreeElemThreadSpecificMarker());
+  auto res = std::unique_ptr<ScheduleTree>(
+      new ScheduleTreeElemThreadSpecificMarker(ctx));
   res->type_ = detail::ScheduleTreeType::ThreadSpecificMarker;
   res->appendChildren(std::move(children));
   return res;

tc/core/polyhedral/schedule_tree_elem.h

@@ -256,9 +256,8 @@ struct ScheduleTreeElemBand : public ScheduleTree {
 struct ScheduleTreeElemThreadSpecificMarker : public ScheduleTree {
   static constexpr detail::ScheduleTreeType NodeType =
       detail::ScheduleTreeType::ThreadSpecificMarker;
-  explicit ScheduleTreeElemThreadSpecificMarker()
-      : ScheduleTree(isl::with_exceptions::globalIslCtx(), {}, NodeType) {
-  } // FIXME: accept a ctx instead of using the global ctx
+  explicit ScheduleTreeElemThreadSpecificMarker(isl::ctx ctx)
+      : ScheduleTree(ctx, {}, NodeType) {}
   virtual ~ScheduleTreeElemThreadSpecificMarker() override {}
   bool operator==(const ScheduleTreeElemThreadSpecificMarker& other) const {
     return true;