Add DoubleToSmi optimistically, preventing boxing/unboxing of doubles and propagate smi-nessof the …

tests/standalone/double_to_int_test.dart

+// Copyright (c) 2012, 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.
+//
+// Tests optimization: transform double.toInt() to DoubleToSmi
+// unless we encounter a non-Smi result, in which case we deoptimize and
+// optimize it later to DoubleToInt.
+
+
+main() {
+  for (int i = 0; i < 600; i++) {
+    Expect.equals(100, foo(100, 1.2));
+  }
+  // Deoptimize 'foo', d2smi -> d2int.
+  Expect.equals(36507222016 * 2, foo(2, 36507222016.6));
+  for (int i = 0; i < 600; i++) {
+    Expect.equals(100, foo(100, 1.2));
+  }
+  Expect.equals(36507222016 * 2, foo(2, 36507222016.6));
+}
+
+
+foo(n, a) {
+  int k = 0;
+  for (int i = 0; i < n; i++) {
+    k += goo(a);
+  }
+  return k;
+}
+
+
+goo(a) {
+  return a.toInt();
+}