Subzero: Use a proper RegNumT type instead of int32_t/SizeT.

src/IceInstX8664.cpp

 //===- subzero/src/IceInstX8664.cpp - X86-64 instruction implementation ---===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 71 matching lines @@
     SizeT I = 0;
     if (Base)
       Vars[I++] = Base;
     if (Index)
       Vars[I++] = Index;
     assert(I == NumVars);
   }
 }
 
 namespace {
-static int32_t
-getRematerializableOffset(Variable *Var,
-                          const ::Ice::X8664::TargetX8664 *Target) {
+int32_t getRematerializableOffset(Variable *Var,
+                                  const ::Ice::X8664::TargetX8664 *Target) {
   int32_t Disp = Var->getStackOffset();
-  SizeT RegNum = static_cast<SizeT>(Var->getRegNum());
+  const auto RegNum = Var->getRegNum();
   if (RegNum == Target->getFrameReg()) {
     Disp += Target->getFrameFixedAllocaOffset();
   } else if (RegNum != Target->getStackReg()) {
     llvm::report_fatal_error("Unexpected rematerializable register type");
   }
   return Disp;
 }
 } // end of anonymous namespace
 
 void TargetX8664Traits::X86OperandMem::emit(const Cfg *Func) const {
@@ skipping 250 matching lines @@
     Var->dump(Func);
   else
     Var->dump(Str);
   Str << ")";
 }
 
 } // namespace X8664
 } // end of namespace Ice
 
 X86INSTS_DEFINE_STATIC_DATA(X8664, X8664::Traits)