diff --git a/src/main/java/org/apidesign/demo/talk2compiler/Main.java b/src/main/java/org/apidesign/demo/talk2compiler/Main.java
index ee6afd9..a47dedf 100644
--- a/src/main/java/org/apidesign/demo/talk2compiler/Main.java
+++ b/src/main/java/org/apidesign/demo/talk2compiler/Main.java
@@ -1,15 +1,18 @@
 package org.apidesign.demo.talk2compiler;
 
 import com.oracle.truffle.api.CallTarget;
-import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.Truffle;
 import com.oracle.truffle.api.frame.VirtualFrame;
+import com.oracle.truffle.api.nodes.Node;
 import com.oracle.truffle.api.nodes.RootNode;
 
 public class Main extends RootNode {
     static final Main MAIN = new Main();
     static final CallTarget CODE = Truffle.getRuntime().createCallTarget(MAIN);
 
+    @Child
+    private Compute compute;
+
     private Main() {
         super(null);
     }
@@ -21,12 +24,45 @@ public static void main(String... args) {
 
     @Override
     public Object execute(VirtualFrame frame) {
-        final String name = (String) frame.getArguments()[0];
-        return formatGreeting("Hello from %s!", name);
+        final int[] name = (int[]) frame.getArguments()[0];
+        return compute.compute(name);
+    }
+
+    void setProgram(Compute program) {
+        compute = insert(program);
     }
 
-    @TruffleBoundary
-    private static String formatGreeting(String msg, String name) {
-        return String.format(msg, name);
+    public static abstract class Compute extends Node {
+        public abstract int compute(int[] arr);
+    }
+
+    public static final class Plus extends Compute {
+        @Child Compute left;
+        @Child Compute right;
+
+        public Plus(Compute left, Compute right) {
+            this.left = left;
+            this.right = right;
+        }
+
+        @Override
+        public int compute(int[] arr) {
+            int leftValue = left.compute(arr);
+            int rightValue = right.compute(arr);
+            return leftValue + rightValue;
+        }
+    }
+
+    public static final class Arg extends Compute {
+        private final int index;
+
+        public Arg(int index) {
+            this.index = index;
+        }
+
+        @Override
+        public int compute(int[] arr) {
+            return arr[index];
+        }
     }
 }
diff --git a/src/test/java/org/apidesign/demo/talk2compiler/MainTest.java b/src/test/java/org/apidesign/demo/talk2compiler/MainTest.java
index fca61a0..fc5cf82 100644
--- a/src/test/java/org/apidesign/demo/talk2compiler/MainTest.java
+++ b/src/test/java/org/apidesign/demo/talk2compiler/MainTest.java
@@ -7,12 +7,18 @@
 public class MainTest {
     @Before
     public void warmingUp() {
+        Main.Plus program = new Main.Plus(
+            new Main.Plus(new Main.Arg(0), new Main.Arg(1)),
+            new Main.Arg(2)
+        );
+        Main.MAIN.setProgram(program);
+
         int count;
         if (Boolean.getBoolean("noigv")) {
             // Skip warmup if IGV dump isn't requested
             count = 1;
         } else {
-            count = 1000000;
+            count = 10000000;
         }
         for (int i = 0; i < count; i++) {
             sayHelloTruffle();
@@ -21,10 +27,11 @@ public void warmingUp() {
 
     @Test
     public void checkSayHello() {
-        Assert.assertEquals("Hello from Truffle!", sayHelloTruffle());
+        Assert.assertEquals(7 + 8 + 2, sayHelloTruffle());
     }
 
     private static Object sayHelloTruffle() {
-        return Main.CODE.call("Truffle");
+        final Object arr = new int[] { 7, 8, 2, 4 };
+        return Main.CODE.call(arr);
     }
 }