Merge functionality of HExactType into HBoundedType and fix computation of unions and intersections.

lib/compiler/implementation/ssa/types_propagation.dart

Index: lib/compiler/implementation/ssa/types_propagation.dart
diff --git a/lib/compiler/implementation/ssa/types_propagation.dart b/lib/compiler/implementation/ssa/types_propagation.dart
index c9d69cce832009193595860533f5f9bc7f946f3b..44dc10b5f2c5503208786e73c69b4086ffc8d375 100644
--- a/lib/compiler/implementation/ssa/types_propagation.dart
+++ b/lib/compiler/implementation/ssa/types_propagation.dart
@@ -27,7 +27,7 @@ class SsaTypePropagator extends HGraphVisitor implements OptimizationPhase {
     // We unconditionally replace the propagated type with the new type. The
     // computeType must make sure that we eventually reach a stable state.
     instruction.propagatedType = newType;
-    return oldType !== newType;
+    return oldType != newType;

[ngeoffray, 2012/05/29 12:16:21]

I would have suggested to introduce a method on Type to avoid the equality being
so brittle, but we're getting rid of triple equality soon, so I should probably
get used to it.

   }
 
   void visitGraph(HGraph graph) {
@@ -52,7 +52,9 @@ class SsaTypePropagator extends HGraphVisitor implements OptimizationPhase {
       });
     } else {
       block.forEachPhi((HPhi phi) {
-        if (updateType(phi)) addDependentInstructionsToWorkList(phi);
+        if (updateType(phi)) {
+          addDependentInstructionsToWorkList(phi);
+        }
       });
     }