[ARITH] More robust int set checking (#487)

src/arithmetic/int_set.cc

@@ -132,27 +132,18 @@ IntSet IntSet::interval(Expr min, Expr max) {
   return IntervalSet::make(min, max);
 }
 
+inline bool prove_equal(Expr lhs, Expr rhs) {
+  return is_zero(ir::Simplify(lhs - rhs));
+}
+
 // Check if a is created from b.
 bool IntSet::match_range(const Range& b) const {
   const IntSet& a = *this;
   const IntervalSet* a_int = a.as<IntervalSet>();
   if (!a_int) return false;
   const Interval& i = a_int->i;
-  if (!i.min.same_as(b)) return false;
-  if (is_one(b->extent)) return i.is_single_point();
-  if (is_positive_const(b->extent) && is_const(b->min)) {
-    // deep equality
-    return Equal(
-        ComputeExpr<Sub>(ComputeExpr<Add>(b->extent, b->min), 1),
-        a_int->i.max);
-  }
-  const Sub* sub = i.max.as<Sub>();
-  if (!sub) return false;
-  if (is_one(sub->b)) return false;
-  const Add* add = sub->a.as<Add>();
-  return add &&
-      add->a.same_as(b->min) &&
-      add->b.same_as(b->extent);
+  return prove_equal(i.min, b->min) &&
+      prove_equal(i.max, ComputeExpr<Sub>(ComputeExpr<Add>(b->extent, b->min), 1));
 }
 
 inline bool MatchPoint(const IntSet& a,