makeIslAffFromExpr: only accept parametric expressions

All the users have been converted to only pass in parametric expressions.
This removes a dependence on the names of set dimensions.

Author: Sven Verdoolaege

tc/core/halide2isl.cc

@@ -174,16 +174,9 @@ std::vector<isl::aff> makeIslAffBoundsFromExpr(
   const Max* maxOp = e.as<Max>();
 
   if (const Variable* op = e.as<Variable>()) {
-    isl::local_space ls = isl::local_space(space);
-    int pos = space.find_dim_by_name(isl::dim_type::param, op->name);
-    if (pos >= 0) {
-      return {isl::aff(ls, isl::dim_type::param, pos)};
-    } else {
-      // FIXME: thou shalt not rely upon set dimension names
-      pos = space.find_dim_by_name(isl::dim_type::set, op->name);
-      if (pos >= 0) {
-        return {isl::aff(ls, isl::dim_type::set, pos)};
-      }
+    isl::id id(space.get_ctx(), op->name);
+    if (space.has_param(id)) {
+      return {isl::aff::param_on_domain_space(space, id)};
     }
     LOG(FATAL) << "Variable not found in isl::space: " << space << ": " << op
                << ": " << op->name << '\n';

tc/core/halide2isl.h

@@ -53,7 +53,10 @@ isl::aff makeIslAffFromInt(isl::space space, int64_t i);
 
 // Make an affine function over a space from a Halide Expr. Returns a
 // null isl::aff if the expression is not affine. Fails if Variable
-// does not correspond to a parameter or set dimension of the space.
+// does not correspond to a parameter of the space.
+// Note that the input space can be either a parameter space or
+// a set space, but the expression can only reference
+// the parameters in the space.
 isl::aff makeIslAffFromExpr(isl::space space, const Halide::Expr& e);
 
 // Iteration domain information associated to a statement identifier.