[Sema] Split special builtin type lookups into a separate function

In case further such cases appear in the future we've got a generic function to add them to.
Additionally changed the ObjC special case to check the language and the identifier builtin ID instead of the name.

Addresses the cleanup suggestion from D87917.

Reviewed By: rjmccall

Differential Revision: https://reviews.llvm.org/D87983

Author: tambry

clang/include/clang/Sema/Sema.h

@@ -3813,6 +3813,7 @@ class Sema final {
                               RedeclarationKind Redecl
                                 = NotForRedeclaration);
   bool LookupBuiltin(LookupResult &R);
+  void LookupNecessaryTypesForBuiltin(Scope *S, unsigned ID);
   bool LookupName(LookupResult &R, Scope *S,
                   bool AllowBuiltinCreation = false);
   bool LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,

clang/lib/Sema/SemaDecl.cpp

@@ -2035,24 +2035,6 @@ Scope *Sema::getNonFieldDeclScope(Scope *S) {
   return S;
 }
 
-/// Looks up the declaration of "struct objc_super" and
-/// saves it for later use in building builtin declaration of
-/// objc_msgSendSuper and objc_msgSendSuper_stret. If no such
-/// pre-existing declaration exists no action takes place.
-static void LookupPredefedObjCSuperType(Sema &ThisSema, Scope *S,
-                                        IdentifierInfo *II) {
-  if (!II->isStr("objc_msgSendSuper"))
-    return;
-  ASTContext &Context = ThisSema.Context;
-
-  LookupResult Result(ThisSema, &Context.Idents.get("objc_super"),
-                      SourceLocation(), Sema::LookupTagName);
-  ThisSema.LookupName(Result, S);
-  if (Result.getResultKind() == LookupResult::Found)
-    if (const TagDecl *TD = Result.getAsSingle<TagDecl>())
-      Context.setObjCSuperType(Context.getTagDeclType(TD));
-}
-
 static StringRef getHeaderName(Builtin::Context &BuiltinInfo, unsigned ID,
                                ASTContext::GetBuiltinTypeError Error) {
   switch (Error) {
@@ -2113,7 +2095,7 @@ FunctionDecl *Sema::CreateBuiltin(IdentifierInfo *II, QualType Type,
 NamedDecl *Sema::LazilyCreateBuiltin(IdentifierInfo *II, unsigned ID,
                                      Scope *S, bool ForRedeclaration,
                                      SourceLocation Loc) {
-  LookupPredefedObjCSuperType(*this, S, II);
+  LookupNecessaryTypesForBuiltin(S, ID);
 
   ASTContext::GetBuiltinTypeError Error;
   QualType R = Context.GetBuiltinType(ID, Error);
@@ -9671,7 +9653,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
             NewFD->addAttr(BuiltinAttr::CreateImplicit(Context, BuiltinID));
           } else {
             ASTContext::GetBuiltinTypeError Error;
-            LookupPredefedObjCSuperType(*this, S, NewFD->getIdentifier());
+            LookupNecessaryTypesForBuiltin(S, BuiltinID);
             QualType BuiltinType = Context.GetBuiltinType(BuiltinID, Error);
 
             if (!Error && !BuiltinType.isNull() &&
@@ -10880,7 +10862,7 @@ bool Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
     // declaration against the expected type for the builtin.
     if (unsigned BuiltinID = NewFD->getBuiltinID()) {
       ASTContext::GetBuiltinTypeError Error;
-      LookupPredefedObjCSuperType(*this, S, NewFD->getIdentifier());
+      LookupNecessaryTypesForBuiltin(S, BuiltinID);
       QualType T = Context.GetBuiltinType(BuiltinID, Error);
       // If the type of the builtin differs only in its exception
       // specification, that's OK.

clang/lib/Sema/SemaLookup.cpp

@@ -907,6 +907,24 @@ bool Sema::LookupBuiltin(LookupResult &R) {
   return false;
 }
 
+/// Looks up the declaration of "struct objc_super" and
+/// saves it for later use in building builtin declaration of
+/// objc_msgSendSuper and objc_msgSendSuper_stret.
+static void LookupPredefedObjCSuperType(Sema &Sema, Scope *S) {
+  ASTContext &Context = Sema.Context;
+  LookupResult Result(Sema, &Context.Idents.get("objc_super"), SourceLocation(),
+                      Sema::LookupTagName);
+  Sema.LookupName(Result, S);
+  if (Result.getResultKind() == LookupResult::Found)
+    if (const TagDecl *TD = Result.getAsSingle<TagDecl>())
+      Context.setObjCSuperType(Context.getTagDeclType(TD));
+}
+
+void Sema::LookupNecessaryTypesForBuiltin(Scope *S, unsigned ID) {
+  if (ID == Builtin::BIobjc_msgSendSuper)
+    LookupPredefedObjCSuperType(*this, S);
+}
+
 /// Determine whether we can declare a special member function within
 /// the class at this point.
 static bool CanDeclareSpecialMemberFunction(const CXXRecordDecl *Class) {