Generalize if-conversion to arbitrary smi comparisons.

tests/language/vm/optimized_testsmi_test.dart

+// Copyright (c) 2013, 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.
+// VMOptions=--optimization_counter_threshold=10
+
+// Test branch optimization for TestSmiInstr
+
+import "package:expect/expect.dart";
+
+test(bool b) {
+  var a = 0;
+  if (b) {
+    a++;
+  } else {
+    a += 2;
+  }
+  if (a & 1 == 0) {
+    return "even";
+  }
+  return "odd";
+}
+
+main() {
+  Expect.equals("odd", test(true));
+  Expect.equals("even", test(false));
+  for (var i=0; i<20; i++) test(false);
+  Expect.equals("odd", test(true));
+  Expect.equals("even", test(false));
+}
+