Add UBSAN build option and fix undefined behaviour errors.

src/IceTargetLoweringX8664Traits.h

 //===- subzero/src/IceTargetLoweringX8664Traits.h - x86-64 traits -*- C++ -*-=//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 547 matching lines @@
   using Assembler = X8664::AssemblerX8664;
 
   /// X86Operand extends the Operand hierarchy.  Its subclasses are
   /// X86OperandMem and VariableSplit.
   class X86Operand : public ::Ice::Operand {
     X86Operand() = delete;
     X86Operand(const X86Operand &) = delete;
     X86Operand &operator=(const X86Operand &) = delete;
 
   public:
-    enum OperandKindX8664 { k__Start = ::Ice::Operand::kTarget, kMem, kSplit };
+    enum OperandKindX8664 { k__Start = ::Ice::Operand::kTarget0, kMem, kSplit };
     using ::Ice::Operand::dump;
 
     void dump(const Cfg *, Ostream &Str) const override;
 
   protected:
     X86Operand(OperandKindX8664 Kind, Type Ty)
         : Operand(static_cast<::Ice::Operand::OperandKind>(Kind), Ty) {}
   };
 
   /// X86OperandMem represents the m64 addressing mode, with optional base and
@@ skipping 99 matching lines @@
   class SpillVariable : public Variable {
     SpillVariable() = delete;
     SpillVariable(const SpillVariable &) = delete;
     SpillVariable &operator=(const SpillVariable &) = delete;
 
   public:
     static SpillVariable *create(Cfg *Func, Type Ty, SizeT Index) {
       return new (Func->allocate<SpillVariable>()) SpillVariable(Ty, Index);
     }
     const static OperandKind SpillVariableKind =
-        static_cast<OperandKind>(kVariable_Target);
+        static_cast<OperandKind>(kVariable_Target0);
     static bool classof(const Operand *Operand) {
       return Operand->getKind() == SpillVariableKind;
     }
     void setLinkedTo(Variable *Var) { LinkedTo = Var; }
     Variable *getLinkedTo() const { return LinkedTo; }
     // Inherit dump() and emit() from Variable.
 
   private:
     SpillVariable(Type Ty, SizeT Index)
         : Variable(SpillVariableKind, Ty, Index), LinkedTo(nullptr) {}
@@ skipping 23 matching lines @@
 
 } // end of namespace X86Internal
 
 namespace X8664 {
 using Traits = ::Ice::X86Internal::MachineTraits<TargetX8664>;
 } // end of namespace X8664
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGX8664TRAITS_H