llvmir some opt

frontend/ast/NodeStack.java

@@ -0,0 +1,23 @@
+package frontend.ast;
+
+import java.util.ArrayList;
+
+public class NodeStack {
+    private ArrayList<Node> stack;
+
+    public NodeStack() {
+        stack = new ArrayList<Node>();
+    }
+
+    public void push(Node node) {
+        stack.add(node);
+    }
+
+    public Node pop() {
+        return stack.remove(stack.size() - 1);
+    }
+
+    public int size() {
+        return stack.size();
+    }
+}