[llvm-exegesis] Re-enable liveliness tracker.

tools/llvm-exegesis/lib/Assembler.cpp

 static constexpr const char ModuleID[] = "ExegesisInfoTest";
 static constexpr const char FunctionID[] = "foo";
 
 static std::vector<llvm::MCInst>
 generateSnippetSetupCode(const ExegesisTarget &ET,
                          const llvm::MCSubtargetInfo *const MSI,
                          llvm::ArrayRef<RegisterValue> RegisterInitialValues,
                          bool &IsSnippetSetupComplete) {
+  IsSnippetSetupComplete = true;
   std::vector<llvm::MCInst> Result;
   for (const RegisterValue &RV : RegisterInitialValues) {
     // Load a constant in the register.
     const auto SetRegisterCode = ET.setRegTo(*MSI, RV.Register, RV.Value);
     if (SetRegisterCode.empty())
       IsSnippetSetupComplete = false;
     Result.insert(Result.end(), SetRegisterCode.begin(), SetRegisterCode.end());
   }
void assembleToStream(const ExegesisTarget &ET,
   // registers.
   auto &Properties = MF.getProperties();
   Properties.set(llvm::MachineFunctionProperties::Property::NoVRegs);
   Properties.reset(llvm::MachineFunctionProperties::Property::IsSSA);
 
   for (const unsigned Reg : LiveIns)
     MF.getRegInfo().addLiveIn(Reg);
 
-  bool IsSnippetSetupComplete = false;
+  bool IsSnippetSetupComplete;
   std::vector<llvm::MCInst> Code =
       generateSnippetSetupCode(ET, TM->getMCSubtargetInfo(),
                                RegisterInitialValues, IsSnippetSetupComplete);
 
   Code.insert(Code.end(), Instructions.begin(), Instructions.end());
 
   // If the snippet setup is not complete, we disable liveliness tracking. This
   // means that we won't know what values are in the registers.