Mark HStringCompareAndBranch as potentially causing GCs.

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 4063 matching lines @@
   HStringCompareAndBranch(HValue* context,
                            HValue* left,
                            HValue* right,
                            Token::Value token)
       : token_(token) {
     ASSERT(Token::IsCompareOp(token));
     SetOperandAt(0, context);
     SetOperandAt(1, left);
     SetOperandAt(2, right);
     set_representation(Representation::Tagged());
+    SetGVNFlag(kChangesNewSpacePromotion);
   }
 
   HValue* context() { return OperandAt(0); }
   HValue* left() { return OperandAt(1); }
   HValue* right() { return OperandAt(2); }
   Token::Value token() const { return token_; }
 
   virtual void PrintDataTo(StringStream* stream);
 
   virtual Representation RequiredInputRepresentation(int index) {
@@ skipping 2694 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_