Correctly set flag indicating a function has references to this symbol

`IsArgSaveRequired` depends on the flag that the function has references to `this` (amongst other conditions) to determine if we need to spill arguments to stack on x64. Since this flag is not set correctly, sometimes we end up not spilling arguments, and therefore have incorrect argument values. Also remove previously unreachable code due to the flag not being set.

Author: nhat-nguyen

lib/Runtime/ByteCode/ByteCodeEmitter.cpp

@@ -1967,7 +1967,7 @@ void ByteCodeGenerator::LoadAllConstants(FuncInfo *funcInfo)
         {
             if (funcInfo->GetThisSymbol())
             {
-            byteCodeFunction->MapAndSetThisRegisterForEventHandler(funcInfo->GetThisSymbol()->GetLocation());
+                byteCodeFunction->MapAndSetThisRegisterForEventHandler(funcInfo->GetThisSymbol()->GetLocation());
             }
             // The environment is the namespace hierarchy starting with "this".
             Assert(!funcInfo->RegIsConst(funcInfo->GetEnvRegister()));

lib/Runtime/ByteCode/ByteCodeGenerator.cpp

@@ -2394,6 +2394,7 @@ void AddVarsToScope(ParseNode *vars, ByteCodeGenerator *byteCodeGenerator)
                 if (sym->IsThis())
                 {
                     funcInfo->SetThisSymbol(sym);
+                    funcInfo->GetParsedFunctionBody()->SetHasThis(true);
                 }
                 else if (sym->IsNewTarget())
                 {

lib/Runtime/Library/GlobalObject.cpp

@@ -686,47 +686,6 @@ using namespace Js;
             pfuncScript->GetFunctionProxy()->EnsureDeserialized();
         }
 
-        if (pfuncScript->GetFunctionBody()->GetHasThis())
-        {
-            // The eval expression refers to "this"
-            if (args.Info.Flags & CallFlags_ExtraArg)
-            {
-                JavascriptFunction* pfuncCaller = nullptr;
-                // If we are non-hidden call to eval then look for the "this" object in the frame display if the caller is a lambda else get "this" from the caller's frame.
-
-                bool successful = false;
-                if (JavascriptStackWalker::GetCaller(&pfuncCaller, scriptContext))
-                {
-                    FunctionInfo* functionInfo = pfuncCaller->GetFunctionInfo();
-                    if (functionInfo != nullptr && (functionInfo->IsLambda() || functionInfo->IsClassConstructor()))
-                    {
-                        Var defaultInstance = (moduleID == kmodGlobal) ? JavascriptOperators::OP_LdRoot(scriptContext)->ToThis() : (Var)JavascriptOperators::GetModuleRoot(moduleID, scriptContext);
-                        varThis = JavascriptOperators::OP_GetThisScoped(environment, defaultInstance, scriptContext);
-                        if (!strictMode)
-                        {
-                            UpdateThisForEval(varThis, moduleID, scriptContext);
-                        }
-                        successful = true;
-                    }
-                }
-
-                if (!successful)
-                {
-                    JavascriptStackWalker::GetThis(&varThis, moduleID, scriptContext);
-                    if (!strictMode)
-                    {
-                        UpdateThisForEval(varThis, moduleID, scriptContext);
-                    }
-                }
-            }
-            else
-            {
-                // The expression, which refers to "this", is evaluated by an indirect eval.
-                // Set "this" to the current module root.
-                varThis = JavascriptOperators::OP_GetThis(scriptContext->GetLibrary()->GetUndefined(), moduleID, scriptContext);
-            }
-        }
-
         if (pfuncScript->HasSuperReference())
         {
             // Indirect evals cannot have a super reference.