Start propagating non-primitive types in the backend, and fold instructions that know about the typ…

lib/compiler/implementation/ssa/types.dart

 // Copyright (c) 2011, 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.
 
 class SsaTypePropagator extends HGraphVisitor implements OptimizationPhase {
 
   final Map<int, HInstruction> workmap;
   final List<int> worklist;
   final Compiler compiler;
   String get name() => 'type propagator';
@@ skipping 113 matching lines @@
     if (oldType.isConflicting()) return oldType;
 
     HType newType = super.computeType(instruction);
     // [computeDesiredType] goes to all usedBys and lets them compute their
     // desired type. By setting the [newType] here we give them more context to
     // work with.
     instruction.propagatedType = newType;
     HType desiredType = computeDesiredType(instruction);
     // If the desired type is conflicting just return the computed type.
     if (desiredType.isConflicting()) return newType;
+    // TODO(ngeoffray): Allow speculative optimizations on
+    // non-primitive types?
+    if (desiredType.isNonPrimitive()) return newType;
     return newType.combine(desiredType);
   }
 }