dart2js cps: Global value numbering and loop-invariant code motion.

tests/compiler/dart2js/js_backend_cps_ir_gvn_test.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Test that the GVN optimization pass works as expected.
+
+library basic_tests;
+
+import 'js_backend_cps_ir.dart';
+
+const List<TestEntry> tests = const [
+  const TestEntry.forMethod('function(foo)', r"""
+foo(x, list) {
+  var sum = 0;
+  for (int k = 0; k < 10; k++) {
+    // Everything can be hoisted out, except the bounds check and sum += z.
+    var a = x.left.left;
+    var b = x.left.right;
+    var c = x.right.left;
+    var d = x.right.right;
+    var i = a.value + c.value;
+    var j = b.value + d.value;
+    var z = list[i * j] + i;
+    sum += z;
+  }
+  return sum;
+}
+// Use a different class for each level in the tree, so type inference
+// is not confused.
+class Root {
+  Branch left, right;
+  Root(this.left, this.right);
+}
+class Branch {
+  Leaf left, right;
+  Branch(this.left, this.right);
+}
+class Leaf {
+  int value;
+  Leaf(this.value);
+}
+main() {
+  var x1 = new Leaf(1);
+  var x2 = new Leaf(10);
+  var x3 = new Leaf(20);
+  var x4 = new Leaf(-10);
+  var y1 = new Branch(x1, x2);
+  var y2 = new Branch(x3, x4);
+  var z  = new Root(y1, y2);
+  print(foo(z, [1,2,3,4,5,6,7,8,9,10]));
+}
+""",r"""
+function(x, list) {
+  var v0 = x.left, a = v0.left, b = v0.right, sum = 0, k = 0, c = (v0 = x.right).left, d = v0.right, i = a.value + c.value, v1 = list[v0 = i * (b.value + d.value)];
+  for (; k < 10; sum = sum + (v1 + i), k = k + 1)
+    if (v0 < 0 || v0 >= 10)
+      H.ioore(list, v0);
+  return sum;
+}"""),
+];
+
+void main() {
+  runTests(tests);
+}