Never hchange nan-hole to hole or hole to nan-hole.

src/hydrogen-representation-changes.cc

 // Copyright 2013 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 29 matching lines @@
   } else {
     next = HInstruction::cast(use_value);
   }
   // For constants we try to make the representation change at compile
   // time. When a representation change is not possible without loss of
   // information we treat constants like normal instructions and insert the
   // change instructions for them.
   HInstruction* new_value = NULL;
   bool is_truncating_to_smi = use_value->CheckFlag(HValue::kTruncatingToSmi);
   bool is_truncating_to_int = use_value->CheckFlag(HValue::kTruncatingToInt32);
-  bool allow_undefined_as_nan =
-      use_value->CheckFlag(HValue::kAllowUndefinedAsNaN);
   if (value->IsConstant()) {
     HConstant* constant = HConstant::cast(value);
     // Try to create a new copy of the constant with the new representation.
     if (is_truncating_to_int && to.IsInteger32()) {
       Maybe<HConstant*> res = constant->CopyToTruncatedInt32(graph()->zone());
       if (res.has_value) new_value = res.value;
     } else {
       new_value = constant->CopyToRepresentation(to, graph()->zone());
     }
   }
 
   if (new_value == NULL) {
-    new_value = new(graph()->zone()) HChange(value, to,
-                                             is_truncating_to_smi,
-                                             is_truncating_to_int,
-                                             allow_undefined_as_nan);
+    new_value = new(graph()->zone()) HChange(
+        value, to, is_truncating_to_smi, is_truncating_to_int);
   }
 
   new_value->InsertBefore(next);
   use_value->SetOperandAt(use_index, new_value);
 }
 
 
 void HRepresentationChangesPhase::InsertRepresentationChangesForValue(
     HValue* value) {
   Representation r = value->representation();
@@ skipping 95 matching lines @@
     // Process normal instructions.
     for (HInstruction* current = block->first(); current != NULL; ) {
       HInstruction* next = current->next();
       InsertRepresentationChangesForValue(current);
       current = next;
     }
   }
 }
 
 } }  // namespace v8::internal