Flexible representation for BuildIncrement, but CannotBeTagged.

src/hydrogen-instructions.cc

 // Copyright 2012 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 110 matching lines @@
 
   return Representation::None();
 }
 
 
 void HValue::UpdateRepresentation(Representation new_rep,
                                   HInferRepresentation* h_infer,
                                   const char* reason) {
   Representation r = representation();
   if (new_rep.is_more_general_than(r)) {
+    if (CheckFlag(kCannotBeTagged) && r.IsTagged()) return;
     if (FLAG_trace_representation) {
       PrintF("Changing #%d %s representation %s -> %s based on %s\n",
              id(), Mnemonic(), r.Mnemonic(), new_rep.Mnemonic(), reason);
     }
     ChangeRepresentation(new_rep);
     AddDependantsToWorklist(h_infer);
   }
 }
 
 
@@ skipping 3730 matching lines @@
     case kBackingStore:
       if (!name_.is_null()) stream->Add(*String::cast(*name_)->ToCString());
       stream->Add("[backing-store]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal