[RFC] use templated isl types tensorElementsSet

Templated isl types require the user to specify the domain and range
universes of isl objects, allowing the compiler to check whether
it makes sense to combine pairs of objects.
This RFC only converts isPromotableToRegistersBelow and some related
functions to illustrate the effect.
The isPromotableToRegistersBelow was already applying operations
correctly, so the code itself did not require any changes.
However, one variable was reused to store different types
of intermediate result and this one had to be split up into
several variables because they now have different types.

Author: Sven Verdoolaege

tc/core/polyhedral/memory_promotion.cc

@@ -407,25 +407,25 @@ namespace {
 // each dimension of the tensor is contrained by the min_aff on the left and
 // by the min_aff + extent_aff on the right.  Intersect this set with the
 // context of the scop.
-isl::set tensorElementsSet(const Scop& scop, isl::id tensorId) {
+isl::Set<Tensor> tensorElementsSet(const Scop& scop, isl::id tensorId) {
   auto halideParameter = scop.findArgument(tensorId).parameter();
   auto space = scop.domain().get_space();
   auto nDim = halideParameter.dimensions();
   auto tensorTuple = constructTensorTuple(space, tensorId, nDim);
   auto tensorSpace = tensorTuple.get_space();
 
-  auto tensorElements = isl::set::universe(tensorSpace);
-  auto identity = isl::multi_aff::identity(tensorSpace.map_from_set());
+  auto tensorElements = isl::Set<Tensor>::universe(tensorSpace);
+  auto identity = isl::MultiAff<Tensor,Tensor>::identity(tensorSpace.map_from_set());
   for (int i = 0; i < nDim; ++i) {
-    isl::aff minAff = halide2isl::makeIslAffFromExpr(
+    auto minAff = halide2isl::makeIslAffFromExpr(
         space, halideParameter.min_constraint(i));
-    isl::aff extentAff = halide2isl::makeIslAffFromExpr(
+    auto extentAff = halide2isl::makeIslAffFromExpr(
         space, halideParameter.extent_constraint(i));
-    minAff = minAff.unbind_params_insert_domain(tensorTuple);
-    extentAff = extentAff.unbind_params_insert_domain(tensorTuple);
+    auto minAff2 = minAff.unbind_params_insert_domain(tensorTuple);
+    auto extentAff2 = extentAff.unbind_params_insert_domain(tensorTuple);
     auto aff = identity.get_aff(i);
-    tensorElements = tensorElements & (minAff <= isl::aff_set(aff)) &
-        (isl::aff_set(aff) < (minAff + extentAff));
+    tensorElements = tensorElements & (minAff2.le_set(aff)) &
+        (aff.lt_set(minAff2 + extentAff2));
   }
 
   tensorElements = tensorElements.intersect_params(scop.context());