Don't force representations in the loop builder.

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 2480 matching lines @@
   stream->Add("B%d", SuccessorAt(0)->block_id());
 }
 
 
 void HCompareIDAndBranch::InferRepresentation(HInferRepresentation* h_infer) {
   Representation left_rep = left()->representation();
   Representation right_rep = right()->representation();
   Representation observed_left = observed_input_representation(0);
   Representation observed_right = observed_input_representation(1);
 
-  Representation rep = Representation::Smi();
-  if (observed_left.IsInteger32() && observed_right.IsInteger32()) {
+  Representation rep = Representation::None();
+  rep = rep.generalize(observed_left);
+  rep = rep.generalize(observed_right);
+  if (rep.IsNone() || rep.IsSmiOrInteger32()) {
     if (!left_rep.IsTagged()) rep = rep.generalize(left_rep);
     if (!right_rep.IsTagged()) rep = rep.generalize(right_rep);
   } else {
     rep = Representation::Double();
   }
 
   if (rep.IsDouble()) {
     // According to the ES5 spec (11.9.3, 11.8.5), Equality comparisons (==, ===
     // and !=) have special handling of undefined, e.g. undefined == undefined
     // is 'true'. Relational comparisons have a different semantic, first
@@ skipping 1289 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