Refactor types in ssa nodes.

lib/compiler/implementation/ssa/types_propagation.dart

Index: lib/compiler/implementation/ssa/types_propagation.dart
diff --git a/lib/compiler/implementation/ssa/types.dart b/lib/compiler/implementation/ssa/types_propagation.dart
similarity index 93%
copy from lib/compiler/implementation/ssa/types.dart
copy to lib/compiler/implementation/ssa/types_propagation.dart
index 0f12bb9e8e1b3d6998147afeddea202411b5822c..5783756dee792936bd639e5149d79331eeac21d2 100644
--- a/lib/compiler/implementation/ssa/types.dart
+++ b/lib/compiler/implementation/ssa/types_propagation.dart
@@ -1,4 +1,4 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
@@ -43,7 +43,9 @@ class SsaTypePropagator extends HGraphVisitor implements OptimizationPhase {
         // type of all other incoming edges as "unitialized" and take this into
         // account when doing the propagation inside the phis. Just setting
         // the [propagatedType] is however easier.
-        phi.propagatedType = phi.inputs[0].propagatedType;
+        if (phi.propagatedType.isUnknown()) {

[ngeoffray, 2012/04/25 11:41:13]

Please add a comment on why the phi may already have a type.

[floitsch, 2012/04/25 19:52:15]

Done.

+          phi.propagatedType = phi.inputs[0].propagatedType;
+        }
         addToWorkList(phi);
       });
     } else {
@@ -110,8 +112,8 @@ class SsaSpeculativeTypePropagator extends SsaTypePropagator {
   HType computeDesiredType(HInstruction instruction) {
     HType desiredType = HType.UNKNOWN;
     for (final user in instruction.usedBy) {
-      desiredType =
-          desiredType.combine(user.computeDesiredTypeForInput(instruction));
+      HType userType = user.computeDesiredTypeForInput(instruction);
+      desiredType = desiredType.intersection(userType);
       // No need to continue if two users disagree on the type.
       if (desiredType.isConflicting()) break;
     }
@@ -134,6 +136,6 @@ class SsaSpeculativeTypePropagator extends SsaTypePropagator {
     // TODO(ngeoffray): Allow speculative optimizations on
     // non-primitive types?
     if (desiredType.isNonPrimitive()) return newType;
-    return newType.combine(desiredType);
+    return newType.intersection(desiredType);
   }
 }