Mark map-transition stores as map-changing instructions....

src/hydrogen.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3147 matching lines @@
     // from the end of the fixed part of the object.
     offset += type->instance_size();
   } else {
     offset += FixedArray::kHeaderSize;
   }
   HStoreNamedField* instr =
       new HStoreNamedField(object, name, value, is_in_object, offset);
   if (lookup->type() == MAP_TRANSITION) {
     Handle<Map> transition(lookup->GetTransitionMapFromMap(*type));
     instr->set_transition(transition);
+    // TODO(fschneider): Record the new map type of the object in the IR to
+    // enable elimination of redundant checks after the transition store.
+    instr->SetFlag(HValue::kChangesMaps);
   }
   return instr;
 }
 
 
 HInstruction* HGraphBuilder::BuildStoreNamedGeneric(HValue* object,
                                                     Handle<String> name,
                                                     HValue* value) {
   return new HStoreNamedGeneric(object, name, value);
 }
@@ skipping 2493 matching lines @@
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify();
   if (chunk_ != NULL) chunk_->Verify();
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal