add insertSequenceBelow

This will be useful in insertCopiesUnder to initialize a sequence
for placing reads before and/or writes after.

Author: Sven Verdoolaege

tc/core/polyhedral/schedule_transforms.cc

@@ -518,6 +518,16 @@ ScheduleTree* insertSequenceAbove(ScheduleTree* root, ScheduleTree* tree) {
   return parent->child({childPos});
 }
 
+void insertSequenceBelow(
+    const detail::ScheduleTree* root,
+    detail::ScheduleTree* tree) {
+  auto numChildren = tree->numChildren();
+  CHECK_LE(numChildren, 1u);
+  auto filter = activeDomainPointsBelow(root, tree).universe();
+  auto node = ScheduleTree::makeFilter(filter, tree->detachChildren());
+  tree->appendChild(ScheduleTree::makeSequence(std::move(node)));
+}
+
 ScheduleTree* insertExtensionAbove(
     ScheduleTree* relativeRoot,
     ScheduleTree* tree,

tc/core/polyhedral/schedule_transforms.h

@@ -167,6 +167,14 @@ detail::ScheduleTree* insertSequenceAbove(
     detail::ScheduleTree* root,
     detail::ScheduleTree* tree);
 
+// In a tree starting at "root", insert a sequence node underneath "tree".
+// "tree" is assumed to have at most one child.
+//
+// The tree is modified in place.
+void insertSequenceBelow(
+    const detail::ScheduleTree* root,
+    detail::ScheduleTree* tree);
+
 // In a tree starting at a "relativeRoot", insert an extension node with the
 // given extension above the node identified by "tree".
 //