Let NaN flow as double into HBranch

src/hydrogen-instructions.h

 // 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 1579 matching lines @@
 
   HValue* value() { return OperandAt(0); }
 };
 
 
 class HBranch: public HUnaryControlInstruction {
  public:
   HBranch(HValue* value,
           HBasicBlock* true_target,
           HBasicBlock* false_target,
-          ToBooleanStub::Types expected_input_types = ToBooleanStub::no_types())
+          ToBooleanStub::Types expected_input_types = ToBooleanStub::Types())
       : HUnaryControlInstruction(value, true_target, false_target),
         expected_input_types_(expected_input_types) {
     ASSERT(true_target != NULL && false_target != NULL);
+    SetFlag(kAllowUndefinedAsNaN);
   }
   explicit HBranch(HValue* value)
-      : HUnaryControlInstruction(value, NULL, NULL) { }
+      : HUnaryControlInstruction(value, NULL, NULL) {
+    SetFlag(kAllowUndefinedAsNaN);
+  }
   HBranch(HValue* value, ToBooleanStub::Types expected_input_types)
       : HUnaryControlInstruction(value, NULL, NULL),
-        expected_input_types_(expected_input_types) { }
-
+        expected_input_types_(expected_input_types) {
+    SetFlag(kAllowUndefinedAsNaN);
+  }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
   virtual Representation observed_input_representation(int index);
 
   ToBooleanStub::Types expected_input_types() const {
     return expected_input_types_;
   }
 
@@ skipping 5019 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_