Scop: do not allow outside users to modify the domain

There is no need for outside users to modify the domain directly.
They should use the appropriate methods.

Author: Sven Verdoolaege

tc/core/polyhedral/scop.cc

@@ -78,7 +78,7 @@ ScopUPtr Scop::makeScop(isl::ctx ctx, const lang::TreeRef& treeRef) {
   return makeScop(ctx, tc2halide::translate(ctx, treeRef));
 }
 
-isl::union_set& Scop::domain() {
+isl::union_set& Scop::domainRef() {
   auto dom = scheduleRoot()->elemAs<ScheduleTreeElemDomain>();
   CHECK(dom) << "root is not a domain in: " << *scheduleRoot();
   // TODO: activate this when the invariant has a chance of working (i.e. we
@@ -92,7 +92,7 @@ isl::union_set& Scop::domain() {
 }
 
 const isl::union_set Scop::domain() const {
-  return const_cast<Scop*>(this)->domain();
+  return const_cast<Scop*>(this)->domainRef();
 }
 
 std::ostream& operator<<(std::ostream& os, const Scop& s) {

tc/core/polyhedral/scop.h

@@ -110,7 +110,7 @@ struct Scop {
 
   // Specialize the Scop with respect to its globalParameterContext.
   void specializeToContext() {
-    domain() = domain().intersect_params(globalParameterContext);
+    domainRef() = domain().intersect_params(globalParameterContext);
     reads = reads.intersect_params(globalParameterContext);
     writes = writes.intersect_params(globalParameterContext);
   }
@@ -489,7 +489,9 @@ struct Scop {
   // state is kept.
   // By analogy with generalized functions, the domain is the "support" part
   // of the ScheduleTree "function".
-  isl::union_set& domain();
+ private:
+  isl::union_set& domainRef();
+ public:
   const isl::union_set domain() const;
   // The parameter values of a specialized Scop.
   std::unordered_map<std::string, int> parameterValues;