Reland "VM: Handle null-comparisons in the flow graph type propagation"

runtime/lib/integers.dart

Index: runtime/lib/integers.dart
diff --git a/runtime/lib/integers.dart b/runtime/lib/integers.dart
index ff755e9c8dd2f9e65f9ef477f8a71029a62fff34..8b7e2b48dffcc493c8fd0f7b5f2dcab6af723a7c 100644
--- a/runtime/lib/integers.dart
+++ b/runtime/lib/integers.dart
@@ -2,6 +2,8 @@
 // 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.
 
+abstract class _int64 implements int {}

[Vyacheslav Egorov (Google), 2017/03/31 10:39:44]

Please add a comment about the reason to have this class.

[Florian Schneider, 2017/03/31 16:39:31]

Done.

+
 abstract class _IntegerImplementation {
   // The Dart class _Bigint extending _IntegerImplementation requires a
   // default constructor.
@@ -454,7 +456,7 @@ abstract class _IntegerImplementation {
   }
 }
 
-class _Smi extends _IntegerImplementation implements int {
+class _Smi extends _IntegerImplementation implements int, _int64 {
   factory _Smi._uninstantiable() {
     throw new UnsupportedError("_Smi can only be allocated by the VM");
   }
@@ -654,7 +656,7 @@ class _Smi extends _IntegerImplementation implements int {
 }
 
 // Represents integers that cannot be represented by Smi but fit into 64bits.
-class _Mint extends _IntegerImplementation implements int {
+class _Mint extends _IntegerImplementation implements int, _int64 {
   factory _Mint._uninstantiable() {
     throw new UnsupportedError("_Mint can only be allocated by the VM");
   }