Consolidate shift processing into utility function

src/IceTargetLoweringX86Base.h

 //===- subzero/src/IceTargetLoweringX86Base.h - x86 lowering ----*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 697 matching lines @@
   typename std::enable_if<!std::is_void<Ret>::value, Ret>::type
   dispatchToConcrete(Ret (Machine::*Method)(Args...), Args &&... args) {
     return (static_cast<Machine *>(this)->*Method)(std::forward<Args>(args)...);
   }
 
   template <typename... Args>
   void dispatchToConcrete(void (Machine::*Method)(Args...), Args &&... args) {
     (static_cast<Machine *>(this)->*Method)(std::forward<Args>(args)...);
   }
 
+  void lowerShift64(InstArithmetic::OpKind Op, Operand *Src0Lo, Operand *Src0Hi,
+                    Operand *Src1Lo, Variable *DestLo, Variable *DestHi);
+
   BoolFolding FoldingInfo;
 };
 } // end of namespace X86Internal
 } // end of namespace Ice
 
 #include "IceTargetLoweringX86BaseImpl.h"
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGX86BASE_H