Tweak register allocation for Math.round and do not use roundsd.

src/ia32/lithium-codegen-ia32.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 268 matching lines @@
                                 LOperand* key,
                                 Representation key_representation,
                                 ElementsKind elements_kind,
                                 uint32_t offset,
                                 uint32_t additional_index = 0);
 
   // Specific math operations - used from DoUnaryMathOperation.
   void EmitIntegerMathAbs(LUnaryMathOperation* instr);
   void DoMathAbs(LUnaryMathOperation* instr);
   void DoMathFloor(LUnaryMathOperation* instr);
-  void DoMathRound(LUnaryMathOperation* instr);
   void DoMathSqrt(LUnaryMathOperation* instr);
   void DoMathLog(LUnaryMathOperation* instr);
   void DoMathTan(LUnaryMathOperation* instr);
   void DoMathCos(LUnaryMathOperation* instr);
   void DoMathSin(LUnaryMathOperation* instr);
 
   // Support for recording safepoint and position information.
   void RecordSafepoint(LPointerMap* pointers,
                        Safepoint::Kind kind,
                        int arguments,
@@ skipping 167 matching lines @@
   LCodeGen* codegen_;
   Label entry_;
   Label exit_;
   Label* external_exit_;
   int instruction_index_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_LITHIUM_CODEGEN_IA32_H_