Scop: use must-sources and kills in dependence analysis

Previous commit introduced must writes in Scop.  Use them in the
dependence analysis as must sources for flow dependences and as kills
for flow and false dependences.

Author: ftynse

src/core/polyhedral/scop.cc

@@ -358,19 +358,29 @@ namespace {
 
 using namespace tc::polyhedral;
 
+// Compute the dependence using the given may/must sources, sinks and kills.
+// Any of the inputs may be an empty (but non-null) union map.
+// Dependence analysis removes the cases transitively covered by a must source
+// or a kill.
 isl::union_map computeDependences(
-    isl::union_map sources,
+    isl::union_map maySources,
+    isl::union_map mustSources,
     isl::union_map sinks,
+    isl::union_map kills,
     isl::schedule schedule) {
   auto uai = isl::union_access_info(sinks);
-  uai = uai.set_may_source(sources);
+  uai = uai.set_may_source(maySources);
+  uai = uai.set_must_source(mustSources);
+  uai = uai.set_kill(kills);
   uai = uai.set_schedule(schedule);
   auto flow = uai.compute_flow();
   return flow.get_may_dependence();
 }
 
-// Do the simplest possible dependence analysis.
-// Live-range reordering needs tagged access relations to be available.
+// Set up schedule constraints by performing the dependence analysis using
+// access relations from "scop". Set up callbacks in the constraints depending
+// on "scheduleOptions".
+//
 // The domain of the constraints is intersected with "restrictDomain" if it is
 // provided.
 isl::schedule_constraints makeScheduleConstraints(
@@ -380,12 +390,16 @@ isl::schedule_constraints makeScheduleConstraints(
   auto schedule = toIslSchedule(scop.scheduleRoot());
   auto firstChildNode = scop.scheduleRoot()->child({0});
   auto reads = scop.reads.domain_factor_domain();
-  auto writes = scop.mayWrites.domain_factor_domain();
+  auto mayWrites = scop.mayWrites.domain_factor_domain();
+  auto mustWrites = scop.mustWrites.domain_factor_domain();
+  auto empty = isl::union_map::empty(mustWrites.get_space());
 
   // RAW
-  auto flowDeps = computeDependences(writes, reads, schedule);
+  auto flowDeps =
+      computeDependences(mayWrites, mustWrites, reads, mustWrites, schedule);
   // WAR and WAW
-  auto falseDeps = computeDependences(writes.unite(reads), writes, schedule);
+  auto falseDeps = computeDependences(
+      mayWrites.unite(reads), empty, mayWrites, mustWrites, schedule);
 
   auto allDeps = flowDeps.unite(falseDeps).coalesce();