extractAccess: extract iterator expressions from identity function

This avoids the use of functions in the C++ interface that
will not be exported in mainline isl.

Author: Sven Verdoolaege

tc/core/halide2isl.cc

@@ -264,15 +264,15 @@ isl::map extractAccess(
   // the allocation could be accessed.
   isl::set access = isl::set::universe(tensorSpace);
 
+  auto identity = isl::multi_aff::identity(tensorSpace.map_from_set());
   for (size_t i = 0; i < args.size(); i++) {
     // Then add one equality constraint per dimension to encode the
     // point in the allocation actually read/written for each point in
     // the iteration space. In the case of gathers or scatters, we may
     // have to leave some things unconstrained.
 
     // The coordinate written to in the range ...
-    auto rangePoint =
-        isl::pw_aff(isl::local_space(tensorSpace), isl::dim_type::set, i);
+    auto rangePoint = identity.get_aff(i);
     // ... equals the coordinate accessed as a function of the parameters.
     auto domainPoint = halide2isl::makeIslAffFromExpr(tensorSpace, args[i]);
     if (!domainPoint.is_null()) {