Remove two unused functions

src/Bounds.cpp

@@ -1857,20 +1857,6 @@ Interval bounds_of_expr_in_scope_with_indent(const Expr &expr, const Scope<Inter
     return b.interval;
 }
 
-Region region_union(const Region &a, const Region &b) {
-    internal_assert(a.size() == b.size()) << "Mismatched dimensionality in region union\n";
-    Region result;
-    for (size_t i = 0; i < a.size(); i++) {
-        Expr min = Min::make(a[i].min, b[i].min);
-        Expr max_a = a[i].min + a[i].extent;
-        Expr max_b = b[i].min + b[i].extent;
-        Expr max_plus_one = Max::make(max_a, max_b);
-        Expr extent = max_plus_one - min;
-        result.emplace_back(simplify(min), simplify(extent));
-    }
-    return result;
-}
-
 }  // namespace
 
 Interval bounds_of_expr_in_scope(const Expr &expr, const Scope<Interval> &scope, const FuncValueBounds &fb, bool const_bound) {

src/SplitTuples.cpp

@@ -36,29 +36,6 @@ class FindCallValueIndices : public IRVisitor {
     }
 };
 
-// Visitor and helper function to test if a piece of IR uses an extern image.
-class UsesExternImage : public IRVisitor {
-    using IRVisitor::visit;
-
-    void visit(const Call *c) override {
-        if (c->call_type == Call::Image) {
-            result = true;
-        } else {
-            IRVisitor::visit(c);
-        }
-    }
-
-public:
-    UsesExternImage() = default;
-    bool result = false;
-};
-
-inline bool uses_extern_image(const Stmt &s) {
-    UsesExternImage uses;
-    s.accept(&uses);
-    return uses.result;
-}
-
 class SplitTuples : public IRMutator {
     using IRMutator::visit;