Propagate class ids using existing type propagation framework.

runtime/vm/flow_graph_optimizer.cc

 // 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.
 
 #include "vm/flow_graph_optimizer.h"
 
 #include "vm/flow_graph_builder.h"
 #include "vm/il_printer.h"
 #include "vm/object_store.h"
 #include "vm/parser.h"
@@ skipping 654 matching lines @@
   // No need to propagate the input types of the bound computation, as long as
   // PhiInstr's are handled as part of JoinEntryInstr.
   // Visit computation and possibly eliminate type check.
   bind->computation()->Accept(this, bind);
   // Cache propagated computation type.
   AbstractType& type = AbstractType::Handle(bind->computation()->CompileType());
   bool changed = bind->SetPropagatedType(type);
   if (changed) {
     still_changing_ = true;
   }
+  // Propagate class ids.
+  intptr_t cid = bind->computation()->ResultCid();
+  changed = bind->SetPropagatedCid(cid);
+  if (changed) {
+    still_changing_ = true;
+  }
 }
 
 
 void FlowGraphTypePropagator::VisitPhi(PhiInstr* phi) {
   // We could set the propagated type of the phi to the least upper bound of its
   // input propagated types. However, keeping all propagated types allows us to
   // optimize method dispatch.
   // TODO(regis): Support a set of propagated types. For now, we compute the
   // least specific of the input propagated types.
   AbstractType& type = AbstractType::Handle(phi->LeastSpecificInputType());
   bool changed = phi->SetPropagatedType(type);
   if (changed) {
     still_changing_ = true;
   }
+  if (phi->propagated_cid() == kDynamicCid) {

[regis, 2012/08/15 22:46:54]

So far, I have tried not to depend on the type of the result of the previous
iteration, but only on the types of the inputs in the current iteration.
In your case, it is not clear to me if a propagated cid could be dynamic in the
first iteration and change in a following one. I think it should be possible.

[srdjan, 2012/08/16 00:34:46]

Done.

+    return;
+  }
+  // Merge class ids: if any two inputs have different class ids than result

[regis, 2012/08/15 22:46:54]

s/than/then/

[srdjan, 2012/08/16 00:34:46]

Done.

+  // is kDynamicCid.
+  for (intptr_t i = 0; i < phi->InputCount(); i++) {
+    intptr_t cid = phi->InputAt(i)->ResultCid();
+    ASSERT(cid != kIllegalCid);
+    changed = phi->SetPropagatedCid(cid);

[regis, 2012/08/15 22:46:54]

This does not look right. You are not merging, but setting the cid of the last
input as the phi's cid.
OK, I understand now when looking at SetPropagatedCid(). See my comment there.

[srdjan, 2012/08/16 00:34:46]

Done.

+    if (changed) {
+      still_changing_ = true;
+    }
+  }
 }
 
 
 void FlowGraphTypePropagator::VisitParameter(ParameterInstr* param) {
   // TODO(regis): Once we inline functions, the propagated type of the formal
   // parameter will reflect the compile type of the passed-in argument.
   // For now, we do not know anything about the argument type and therefore set
   // it to the DynamicType, unless the argument is a compiler generated value,
   // i.e. the receiver argument or the constructor phase argument.
   AbstractType& param_type = AbstractType::Handle(Type::DynamicType());
@@ skipping 31 matching lines @@
       LocationSummary* locs = it.Current()->locs();
       if ((locs != NULL) && locs->can_call()) {
         is_leaf_ = false;
         return;
       }
     }
   }
 }
 
 }  // namespace dart