Fixup redefinitions before doing code motion

tests/language/vm/regress_licm_test.dart

+// Copyright (c) 2017, 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=--enable-inlining-annotations --optimization-counter-threshold=1000 --no-background-compilation
+
+// Regression test for correct LICM and type propagation.
+
+const AlwaysInline = "AlwaysInline";
+const NeverInline = "NeverInline";
+
+class Attribute {
+  final id = 123;
+}
+
+class Name {
+  Name(this.name);
+  final String name;
+  get attr;
+
+  @AlwaysInline
+  int compareTo(other) {
+    int nameCompare = name.compareTo(other.name);
+    if (nameCompare != 0) return nameCompare;
+    if (attr == null) return 0;
+    return attr.id - other.attr.id;
+  }
+}
+
+class AName extends Name {
+  AName() : super("abc");
+  final attr = new Attribute();
+}
+
+class BName extends Name {
+  BName(name) : super(name);
+  get attr => null;
+}
+
+
+class Member {
+  Member(this.name);
+  var name;
+}
+
+
+Member find(List<Member> members, Name name) {
+  int low = 0, high = members.length - 1;
+  while (low <= high) {
+    int mid = low + ((high - low) >> 1);
+    Member pivot = members[mid];
+    int comparison = name.compareTo(pivot.name);
+    if (comparison < 0) {
+      high = mid - 1;
+    } else if (comparison > 0) {
+      low = mid + 1;
+    } else {
+      return pivot;
+    }
+  }
+  return null;
+}
+
+
+main() {
+  var list = [new Member(new AName()),
+              new Member(new BName("a")),
+              new Member(new BName("b")),
+              new Member(new BName("c")),
+              new Member(new BName("d"))
+              ];
+
+  find(list, new AName());
+  find(list, new BName("e"));
+  find(list, new BName("b"));
+  for (var i = 0; i < 1000; ++i) {
+    find(list, new BName("b"));
+    find(list, new BName("e"));
+  }
+}