[clang] [clang] Fix PointerAuth semantics of cpp_trivially_relocatable (PR #143969)

[Oliver Hunt via cfe-commits]

================
@@ -629,25 +629,46 @@ class ASTContext : public RefCountedBase<ASTContext> {
   void setRelocationInfoForCXXRecord(const CXXRecordDecl *,
                                      CXXRecordDeclRelocationInfo);
 
-  /// Examines a given type, and returns whether the T itself
+  /// Examines a given type, and returns whether the type itself
   /// is address discriminated, or any transitively embedded types
   /// contain data that is address discriminated. This includes
   /// implicitly authenticated values like vtable pointers, as well as
   /// explicitly qualified fields.
-  bool containsAddressDiscriminatedPointerAuth(QualType T);
-  // A simple helper function to short circuit pointer auth checks.
+  bool containsAddressDiscriminatedPointerAuth(QualType T) {
+    if (!isPointerAuthenticationAvailable())
+      return false;
+    return findPointerAuthContent(T) != PointerAuthContent::None;
+  }
----------------
ojhunt wrote:

Ah right, this is used for the union check - in a union it does not matter what the source of the address discrimination is, a union containing anything address discriminated isn't valid. In principle with this change the only thing that would get here is a vtable pointer but it seems reasonable to be safe.

https://github.com/llvm/llvm-project/pull/143969