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 84%
copy from lib/compiler/implementation/ssa/types.dart
copy to lib/compiler/implementation/ssa/types_propagation.dart
index 0f12bb9e8e1b3d6998147afeddea202411b5822c..a147f5e8e3ef26344bbd5fdb1a0e930e9a5c1ac5 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.
 
@@ -39,11 +39,16 @@ class SsaTypePropagator extends HGraphVisitor implements OptimizationPhase {
   visitBasicBlock(HBasicBlock block) {
     if (block.isLoopHeader()) {
       block.forEachPhi((HPhi phi) {
-        // Set the initial type for the phi. In theory we would need to mark the
-        // 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;
+        // Once the propagation has run once the propagated type can already
+        // be set. In this case we use that one for the first iteration of the
+        // loop.
+        if (phi.propagatedType.isUnknown()) {
+          // Set the initial type for the phi. In theory we would need to mark
+          // the 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;
+        }
         addToWorkList(phi);
       });
     } else {
@@ -110,8 +115,8 @@ 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 +139,6 @@ 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);
   }
 }