add prefixMappingFilter

This will be used in the next commit.

Author: Sven Verdoolaege

tc/core/polyhedral/schedule_transforms.cc

@@ -112,6 +112,16 @@ isl::union_set applyAnyFilter(isl::union_set domain, const ScheduleTree* node) {
   return domain;
 }
 
+/*
+ * If "node" is a mapping filter, then intersect "domain" with that filter.
+ */
+isl::union_set applyMapping(isl::union_set domain, const ScheduleTree* node) {
+  if (auto filterElem = node->elemAs<ScheduleTreeElemMappingFilter>()) {
+    return domain.intersect(filterElem->filter_);
+  }
+  return domain;
+}
+
 // Get the set of domain elements that are active below
 // the given branch of nodes, filtered using "filter".
 //
@@ -150,6 +160,12 @@ isl::union_set activeDomainPointsHelper(
 
 } // namespace
 
+isl::union_set prefixMappingFilter(
+    const ScheduleTree* root,
+    const ScheduleTree* node) {
+  return collectDomain(root, node->ancestors(root), &applyMapping);
+}
+
 isl::union_set activeDomainPoints(
     const ScheduleTree* root,
     const ScheduleTree* node) {

tc/core/polyhedral/schedule_transforms.h

@@ -335,6 +335,12 @@ isl::union_set activeDomainPointsNoMappingNoExtension(
     const detail::ScheduleTree* root,
     const detail::ScheduleTree* tree);
 
+// Collect the outer block/thread identifier mappings
+// into a filter on the active domain elements.
+isl::union_set prefixMappingFilter(
+    const detail::ScheduleTree* root,
+    const detail::ScheduleTree* node);
+
 // Extract a mapping from the domain elements active at "tree" (in a tree
 // rooted at "root") to identifiers "ids", where all branches in "tree" are
 // assumed to have been mapped to these identifiers.  The result lives in a