[clang] [clang][PAC] add support for options parameter to __ptrauth (PR #136828)

[Oliver Hunt via cfe-commits]

================
@@ -8373,10 +8375,140 @@ static void HandlePtrAuthQualifier(ASTContext &Ctx, QualType &T,
                                                    IsAddressDiscriminated);
   IsInvalid |= !S.checkPointerAuthDiscriminatorArg(
       ExtraDiscriminatorArg, PointerAuthDiscArgKind::Extra, ExtraDiscriminator);
+  std::string LastAuthenticationMode;
+  std::optional<PointerAuthenticationMode> AuthenticationMode = std::nullopt;
+  bool IsIsaPointer = false;
+  bool AuthenticatesNullValues = false;
+
+  if (AuthenticationOptionsArg && !AuthenticationOptionsArg->containsErrors()) {
+    StringRef OptionsString;
+    std::string EvaluatedString;
+    bool HasEvaluatedOptionsString = false;
+    const StringLiteral *OptionsStringLiteral =
+        dyn_cast<StringLiteral>(AuthenticationOptionsArg);
+    SourceRange AuthenticationOptionsRange =
+        AuthenticationOptionsArg->getSourceRange();
+    bool ReportedEvaluation = false;
+    auto ReportEvaluationOfExpressionIfNeeded = [&]() {
+      if (OptionsStringLiteral || !HasEvaluatedOptionsString ||
+          ReportedEvaluation)
+        return;
+      ReportedEvaluation = true;
+      S.Diag(AuthenticationOptionsRange.getBegin(),
+             diag::note_ptrauth_evaluating_options)
+          << OptionsString << AuthenticationOptionsRange;
+    };
+    auto DiagnoseInvalidOptionsParameter = [&](llvm::StringRef Reason) {
+      S.Diag(AuthenticationOptionsRange.getBegin(),
+             diag::err_ptrauth_invalid_option)
+          << AttrName << Reason;
+      Attr.setInvalid();
+      IsInvalid = true;
+      ReportEvaluationOfExpressionIfNeeded();
+    };
+    if (AuthenticationOptionsArg->isValueDependent() ||
+        AuthenticationOptionsArg->isTypeDependent()) {
+      DiagnoseInvalidOptionsParameter("is dependent");
+      return;
+    }
+    if (OptionsStringLiteral) {
+      OptionsString = OptionsStringLiteral->getString();
+      HasEvaluatedOptionsString = true;
+    } else {
+      Expr::EvalResult Eval;
+      bool Result = AuthenticationOptionsArg->EvaluateAsRValue(Eval, Ctx);
+      if (Result && Eval.Val.isLValue()) {
----------------
ojhunt wrote:

This section can be replaced once https://github.com/llvm/llvm-project/pull/135864 or similar is landed as it supports const char* constant expressions

https://github.com/llvm/llvm-project/pull/136828