Change some explicit type checks into using helper functions.

src/IceRegistersX8632.h

 //===- subzero/src/IceRegistersX8632.h - Register information ---*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the registers and their encodings for x86-32.
@@ skipping 67 matching lines @@
 }
 
 static inline ByteRegister getEncodedByteReg(int32_t RegNum) {
   assert(RegNum == Reg_ah || (Reg_GPR_First <= RegNum && RegNum <= Reg_ebx));
   if (RegNum == Reg_ah)
     return Encoded_Reg_ah;
   return ByteRegister(RegNum - Reg_GPR_First);
 }
 
 static inline GPRRegister getEncodedByteRegOrGPR(Type Ty, int32_t RegNum) {
-  if (Ty == IceType_i8 || Ty == IceType_i1)
+  if (isByteSizedType(Ty))
     return GPRRegister(getEncodedByteReg(RegNum));
   else
     return getEncodedGPR(RegNum);
 }
 
 } // end of namespace RegX8632
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEREGISTERSX8632_H