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

pkg/compiler/lib/src/cps_ir/type_mask_system.dart

Index: pkg/compiler/lib/src/cps_ir/type_mask_system.dart
diff --git a/pkg/compiler/lib/src/cps_ir/type_mask_system.dart b/pkg/compiler/lib/src/cps_ir/type_mask_system.dart
index a36f2843e8bd3d1f7a768a7acc0c4073e15a5509..58d7330cc754175d428d52499d86a7e1c60d0ad0 100644
--- a/pkg/compiler/lib/src/cps_ir/type_mask_system.dart
+++ b/pkg/compiler/lib/src/cps_ir/type_mask_system.dart
@@ -347,8 +347,12 @@ class TypeMaskSystem {
   }
 
   bool areDisjoint(TypeMask leftType, TypeMask rightType) {
-    TypeMask intersection = leftType.intersection(rightType, classWorld);
-    return intersection.isEmpty && !intersection.isNullable;
+    TypeMask intersected = intersection(leftType, rightType);
+    return intersected.isEmpty && !intersected.isNullable;
+  }
+
+  bool isMorePreciseOrEqual(TypeMask t1, TypeMask t2) {
+    return t2.containsMask(t1, classWorld);
   }
 
   AbstractBool isSubtypeOf(TypeMask value,