Subzero: Prototype to make use of RegNumT::No Register more concise

src/IceTargetLoweringX8664.cpp

 //===- subzero/src/IceTargetLoweringX8664.cpp - x86-64 lowering -----------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 401 matching lines @@
   if (Offset != nullptr) {
     if (const auto *CR = llvm::dyn_cast<ConstantRelocatable>(Offset)) {
       NeedsLea = CR->getName() != "" || CR->getOffset() < 0;
     } else if (const auto *Imm = llvm::dyn_cast<ConstantInteger32>(Offset)) {
       NeedsLea = Imm->getValue() < 0;
     } else {
       llvm::report_fatal_error("Unexpected Offset type.");
     }
   }
 
-  auto RegNum = RegNumT::NoRegister;
-  auto RegNum32 = RegNumT::NoRegister;
+  RegNumT RegNum, RegNum32;
   if (T != nullptr) {
     if (T->hasReg()) {
       RegNum = Traits::getGprForType(IceType_i64, T->getRegNum());
       RegNum32 = Traits::getGprForType(IceType_i32, RegNum);
       // At this point, if T was assigned to rsp/rbp, then we would have already
       // made this the ZeroReg.
       assert(RegNum != Traits::RegisterSet::Reg_rsp);
       assert(RegNum != Traits::RegisterSet::Reg_rbp);
     }
 
@@ skipping 372 matching lines @@
 #define X(tag, sizeLog2, align, elts, elty, str, rcstr)                        \
   static_assert(_table1_##tag == _table2_##tag,                                \
                 "Inconsistency between ICETYPEX8664_TABLE and ICETYPE_TABLE");
 ICETYPE_TABLE
 #undef X
 } // end of namespace dummy3
 } // end of anonymous namespace
 
 } // end of namespace X8664
 } // end of namespace Ice